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<h1 id="overview"><a class="header" href="#overview">Overview</a></h1>
<p>Filament is a physically based rendering (PBR) engine for Android. Filament
offers a customizable material system that you can use to create both simple and
complex materials. This document describes all the features available to
materials and how to create your own material.</p>
<h2 id="core-concepts"><a class="header" href="#core-concepts">Core concepts</a></h2>
<p>Material
: A material defines the visual appearance of a surface. To completely
describe and render a surface, a material provides the following
information:
- Material model
- Set of use-controllable named parameters
- Raster state (blending mode, backface culling, etc.)
- Vertex shader code
- Fragment shader code</p>
<p>Material model
: Also called <em>shading model</em> or <em>lighting model</em>, the material model defines
the intrinsic properties of a surface. These properties have a direct
influence on the way lighting is computed and therefore on the appearance of
a surface.</p>
<p>Material definition
: A text file that describes all the information required by a material. This
is the file that you will directly author to create new materials.</p>
<p>Material package
: At runtime, materials are loaded from <em>material packages</em> compiled from
material definitions using the <code>matc</code> tool. A material package contains all
the information required to describe a material, and shaders generated for
the target runtime platforms. This is necessary because different platforms
(Android, macOS, Linux, etc.) use different graphics APIs or different
variants of similar graphics APIs (OpenGL vs OpenGL ES for instance).</p>
<p>Material instance
: A material instance is a reference to a material and a set of values for the
different values of that material. Material instances are not covered in
this document as they are created and manipulated directly from code using
Filament's APIs.</p>
<h1 id="material-models"><a class="header" href="#material-models">Material models</a></h1>
<p>Filament materials can use one of the following material models: - Lit (or
standard) - Subsurface - Cloth - Unlit - Specular glossiness (legacy)</p>
<h2 id="lit-model"><a class="header" href="#lit-model">Lit model</a></h2>
<p>The lit model is Filament's standard material model. This physically-based
shading model was designed after to offer good interoperability with other
common tools and engines such as <em>Unity 5</em>, <em>Unreal Engine 4</em>, <em>Substance
Designer</em> or <em>Marmoset Toolbag</em>.</p>
<p>This material model can be used to describe many non-metallic surfaces
(<em>dielectrics</em>) or metallic surfaces (<em>conductors</em>).</p>
<p>The appearance of a material using the standard model is controlled using the
properties described in table [standardProperties].</p>
<div class="table-wrapper"><table><thead><tr><th style="text-align: right">Property</th><th style="text-align: left">Definition</th></tr></thead><tbody>
<tr><td style="text-align: right"><strong>baseColor</strong></td><td style="text-align: left">Diffuse albedo for non-metallic surfaces, and specular color for metallic surfaces</td></tr>
<tr><td style="text-align: right"><strong>metallic</strong></td><td style="text-align: left">Whether a surface appears to be dielectric (0.0) or conductor (1.0). Often used as a binary value (0 or 1)</td></tr>
<tr><td style="text-align: right"><strong>roughness</strong></td><td style="text-align: left">Perceived smoothness (1.0) or roughness (0.0) of a surface. Smooth surfaces exhibit sharp reflections</td></tr>
<tr><td style="text-align: right"><strong>reflectance</strong></td><td style="text-align: left">Fresnel reflectance at normal incidence for dielectric surfaces. This directly controls the strength of the reflections</td></tr>
<tr><td style="text-align: right"><strong>sheenColor</strong></td><td style="text-align: left">Strength of the sheen layer</td></tr>
<tr><td style="text-align: right"><strong>sheenRoughness</strong></td><td style="text-align: left">Perceived smoothness or roughness of the sheen layer</td></tr>
<tr><td style="text-align: right"><strong>clearCoat</strong></td><td style="text-align: left">Strength of the clear coat layer</td></tr>
<tr><td style="text-align: right"><strong>clearCoatRoughness</strong></td><td style="text-align: left">Perceived smoothness or roughness of the clear coat layer</td></tr>
<tr><td style="text-align: right"><strong>anisotropy</strong></td><td style="text-align: left">Amount of anisotropy in either the tangent or bitangent direction</td></tr>
<tr><td style="text-align: right"><strong>anisotropyDirection</strong></td><td style="text-align: left">Local surface direction in tangent space</td></tr>
<tr><td style="text-align: right"><strong>ambientOcclusion</strong></td><td style="text-align: left">Defines how much of the ambient light is accessible to a surface point. It is a per-pixel shadowing factor between 0.0 and 1.0</td></tr>
<tr><td style="text-align: right"><strong>normal</strong></td><td style="text-align: left">A detail normal used to perturb the surface using <em>bump mapping</em> (<em>normal mapping</em>)</td></tr>
<tr><td style="text-align: right"><strong>bentNormal</strong></td><td style="text-align: left">A normal pointing in the average unoccluded direction. Can be used to improve indirect lighting quality</td></tr>
<tr><td style="text-align: right"><strong>clearCoatNormal</strong></td><td style="text-align: left">A detail normal used to perturb the clear coat layer using <em>bump mapping</em> (<em>normal mapping</em>)</td></tr>
<tr><td style="text-align: right"><strong>emissive</strong></td><td style="text-align: left">Additional diffuse albedo to simulate emissive surfaces (such as neons, etc.) This property is mostly useful in an HDR pipeline with a bloom pass</td></tr>
<tr><td style="text-align: right"><strong>postLightingColor</strong></td><td style="text-align: left">Additional color that can be blended with the result of the lighting computations. See <code>postLightingBlending</code></td></tr>
<tr><td style="text-align: right"><strong>ior</strong></td><td style="text-align: left">Index of refraction, either for refractive objects or as an alternative to reflectance</td></tr>
<tr><td style="text-align: right"><strong>transmission</strong></td><td style="text-align: left">Defines how much of the diffuse light of a dielectric is transmitted through the object, in other words this defines how transparent an object is</td></tr>
<tr><td style="text-align: right"><strong>absorption</strong></td><td style="text-align: left">Absorption factor for refractive objects</td></tr>
<tr><td style="text-align: right"><strong>microThickness</strong></td><td style="text-align: left">Thickness of the thin layer of refractive objects</td></tr>
<tr><td style="text-align: right"><strong>thickness</strong></td><td style="text-align: left">Thickness of the solid volume of refractive objects</td></tr>
</tbody></table>
</div>
<p>[Table [standardProperties]: Properties of the standard model]</p>
<p>The type and range of each property is described in table
[standardPropertiesTypes].</p>
<div class="table-wrapper"><table><thead><tr><th style="text-align: right">Property</th><th style="text-align: center">Type</th><th style="text-align: center">Range</th><th style="text-align: left">Note</th></tr></thead><tbody>
<tr><td style="text-align: right"><strong>baseColor</strong></td><td style="text-align: center">float4</td><td style="text-align: center">[0..1]</td><td style="text-align: left">Pre-multiplied linear RGB</td></tr>
<tr><td style="text-align: right"><strong>metallic</strong></td><td style="text-align: center">float</td><td style="text-align: center">[0..1]</td><td style="text-align: left">Should be 0 or 1</td></tr>
<tr><td style="text-align: right"><strong>roughness</strong></td><td style="text-align: center">float</td><td style="text-align: center">[0..1]</td><td style="text-align: left"></td></tr>
<tr><td style="text-align: right"><strong>reflectance</strong></td><td style="text-align: center">float</td><td style="text-align: center">[0..1]</td><td style="text-align: left">Prefer values &gt; 0.35</td></tr>
<tr><td style="text-align: right"><strong>sheenColor</strong></td><td style="text-align: center">float3</td><td style="text-align: center">[0..1]</td><td style="text-align: left">Linear RGB</td></tr>
<tr><td style="text-align: right"><strong>sheenRoughness</strong></td><td style="text-align: center">float</td><td style="text-align: center">[0..1]</td><td style="text-align: left"></td></tr>
<tr><td style="text-align: right"><strong>clearCoat</strong></td><td style="text-align: center">float</td><td style="text-align: center">[0..1]</td><td style="text-align: left">Should be 0 or 1</td></tr>
<tr><td style="text-align: right"><strong>clearCoatRoughness</strong></td><td style="text-align: center">float</td><td style="text-align: center">[0..1]</td><td style="text-align: left"></td></tr>
<tr><td style="text-align: right"><strong>anisotropy</strong></td><td style="text-align: center">float</td><td style="text-align: center">[-1..1]</td><td style="text-align: left">Anisotropy is in the tangent direction when this value is positive</td></tr>
<tr><td style="text-align: right"><strong>anisotropyDirection</strong></td><td style="text-align: center">float3</td><td style="text-align: center">[0..1]</td><td style="text-align: left">Linear RGB, encodes a direction vector in tangent space</td></tr>
<tr><td style="text-align: right"><strong>ambientOcclusion</strong></td><td style="text-align: center">float</td><td style="text-align: center">[0..1]</td><td style="text-align: left"></td></tr>
<tr><td style="text-align: right"><strong>normal</strong></td><td style="text-align: center">float3</td><td style="text-align: center">[0..1]</td><td style="text-align: left">Linear RGB, encodes a direction vector in tangent space</td></tr>
<tr><td style="text-align: right"><strong>bentNormal</strong></td><td style="text-align: center">float3</td><td style="text-align: center">[0..1]</td><td style="text-align: left">Linear RGB, encodes a direction vector in tangent space</td></tr>
<tr><td style="text-align: right"><strong>clearCoatNormal</strong></td><td style="text-align: center">float3</td><td style="text-align: center">[0..1]</td><td style="text-align: left">Linear RGB, encodes a direction vector in tangent space</td></tr>
<tr><td style="text-align: right"><strong>emissive</strong></td><td style="text-align: center">float4</td><td style="text-align: center">rgb=[0..n], a=[0..1]</td><td style="text-align: left">Linear RGB intensity in nits, alpha encodes the exposure weight</td></tr>
<tr><td style="text-align: right"><strong>postLightingColor</strong></td><td style="text-align: center">float4</td><td style="text-align: center">[0..1]</td><td style="text-align: left">Pre-multiplied linear RGB</td></tr>
<tr><td style="text-align: right"><strong>ior</strong></td><td style="text-align: center">float</td><td style="text-align: center">[1..n]</td><td style="text-align: left">Optional, usually deduced from the reflectance</td></tr>
<tr><td style="text-align: right"><strong>transmission</strong></td><td style="text-align: center">float</td><td style="text-align: center">[0..1]</td><td style="text-align: left"></td></tr>
<tr><td style="text-align: right"><strong>absorption</strong></td><td style="text-align: center">float3</td><td style="text-align: center">[0..n]</td><td style="text-align: left"></td></tr>
<tr><td style="text-align: right"><strong>microThickness</strong></td><td style="text-align: center">float</td><td style="text-align: center">[0..n]</td><td style="text-align: left"></td></tr>
<tr><td style="text-align: right"><strong>thickness</strong></td><td style="text-align: center">float</td><td style="text-align: center">[0..n]</td><td style="text-align: left"></td></tr>
</tbody></table>
</div>
<p>[Table [standardPropertiesTypes]: Range and type of the standard model's properties]</p>
<p>!!! Note: About linear RGB Several material model properties expect RGB colors.
Filament materials use RGB colors in linear space and you must take proper care
of supplying colors in that space. See the Linear colors section for more
information.</p>
<p>!!! Note: About pre-multiplied RGB Filament materials expect colors to use
pre-multiplied alpha. See the Pre-multiplied alpha section for more information.</p>
<p>!!! Note: About <code>absorption</code> The light attenuation through the material is
defined as \(e^{-absorption \cdot distance}\), and the distance depends on the
<code>thickness</code> parameter. If <code>thickness</code> is not provided, then the <code>absorption</code>
parameter is used directly and the light attenuation through the material
becomes \(1 - absorption\). To obtain a certain color at a desired distance, the
above equation can be inverted such as $absorption =
-\frac{ln(color)}{distance}$.</p>
<p>!!! Note: About <code>ior</code> and <code>reflectance</code> The index of refraction (IOR) and the
reflectance represent the same physical attribute, therefore they don't need to
be both specified. Typically, only the reflectance is specified, and the IOR is
deduced automatically. When only the IOR is specified, the reflectance is then
deduced automatically. It is possible to specify both, in which case their
values are kept as-is, which can lead to physically impossible materials,
however, this might be desirable for artistic reasons.</p>
<p>!!! Note: About <code>thickness</code> and <code>microThickness</code> for refraction <code>thickness</code>
represents the thickness of solid objects in the direction of the normal, for
satisfactory results, this should be provided per fragment (e.g.: as a texture)
or at least per vertex. <code>microThickness</code> represent the thickness of the thin
layer of an object, and can generally be provided as a constant value. For
example, a 1mm thin hollow sphere of radius 1m, would have a <code>thickness</code> of 1
and a <code>microThickness</code> of 0.001. Currently <code>thickness</code> is not used when
<code>refractionType</code> is set to <code>thin</code>.</p>
<h3 id="base-color"><a class="header" href="#base-color">Base color</a></h3>
<p>The <code>baseColor</code> property defines the perceived color of an object (sometimes
called albedo). The effect of <code>baseColor</code> depends on the nature of the surface,
controlled by the <code>metallic</code> property explained in the Metallic section.</p>
<p>Non-metals (dielectrics)
: Defines the diffuse color of the surface. Real-world values are typically
found in the range \([10..240]\) if the value is encoded between 0 and 255, or
in the range \([0.04..0.94]\) between 0 and 1. Several examples of base colors
for non-metallic surfaces can be found in table [baseColorsDielectrics].</p>
<div class="table-wrapper"><table><thead><tr><th style="text-align: right">Metal</th><th style="text-align: center">sRGB</th><th style="text-align: center">Hexadecimal</th><th>Color</th></tr></thead><tbody>
<tr><td style="text-align: right">Coal</td><td style="text-align: center">0.19, 0.19, 0.19</td><td style="text-align: center">#323232</td><td><div style="background-color: #323232; width: 60px"> </div></td></tr>
<tr><td style="text-align: right">Rubber</td><td style="text-align: center">0.21, 0.21, 0.21</td><td style="text-align: center">#353535</td><td><div style="background-color: #353535; width: 60px"> </div></td></tr>
<tr><td style="text-align: right">Mud</td><td style="text-align: center">0.33, 0.24, 0.19</td><td style="text-align: center">#553d31</td><td><div style="background-color: #875c3c; width: 60px"> </div></td></tr>
<tr><td style="text-align: right">Wood</td><td style="text-align: center">0.53, 0.36, 0.24</td><td style="text-align: center">#875c3c</td><td><div style="background-color: #c4c6c6; width: 60px"> </div></td></tr>
<tr><td style="text-align: right">Vegetation</td><td style="text-align: center">0.48, 0.51, 0.31</td><td style="text-align: center">#7b824e</td><td><div style="background-color: #7b824e; width: 60px"> </div></td></tr>
<tr><td style="text-align: right">Brick</td><td style="text-align: center">0.58, 0.49, 0.46</td><td style="text-align: center">#947d75</td><td><div style="background-color: #947d75; width: 60px"> </div></td></tr>
<tr><td style="text-align: right">Sand</td><td style="text-align: center">0.69, 0.66, 0.52</td><td style="text-align: center">#b1a884</td><td><div style="background-color: #b1a884; width: 60px"> </div></td></tr>
<tr><td style="text-align: right">Concrete</td><td style="text-align: center">0.75, 0.75, 0.73</td><td style="text-align: center">#c0bfbb</td><td><div style="background-color: #c0bfbb; width: 60px"> </div></td></tr>
</tbody></table>
</div>
<p>[Table [baseColorsDielectrics]: <code>baseColor</code> for common non-metals]</p>
<p>Metals (conductors)
: Defines the specular color of the surface. Real-world values are typically found in the range
\([170..255]\) if the value is encoded between 0 and 255, or in the range \([0.66..1.0]\)
between 0 and 1. Several examples of base colors for metallic surfaces can be found in table
[baseColorsConductors].</p>
<div class="table-wrapper"><table><thead><tr><th style="text-align: right">Metal</th><th style="text-align: center">sRGB</th><th style="text-align: center">Hexadecimal</th><th>Color</th></tr></thead><tbody>
<tr><td style="text-align: right">Silver</td><td style="text-align: center">0.97, 0.96, 0.91</td><td style="text-align: center">#f7f4e8</td><td><div style="background-color: #faf9f5; width: 60px"> </div></td></tr>
<tr><td style="text-align: right">Aluminum</td><td style="text-align: center">0.91, 0.92, 0.92</td><td style="text-align: center">#e8eaea</td><td><div style="background-color: #f4f5f5; width: 60px"> </div></td></tr>
<tr><td style="text-align: right">Titanium</td><td style="text-align: center">0.76, 0.73, 0.69</td><td style="text-align: center">#c1baaf</td><td><div style="background-color: #cec8c2; width: 60px"> </div></td></tr>
<tr><td style="text-align: right">Iron</td><td style="text-align: center">0.77, 0.78, 0.78</td><td style="text-align: center">#c4c6c6</td><td><div style="background-color: #c0bdba; width: 60px"> </div></td></tr>
<tr><td style="text-align: right">Platinum</td><td style="text-align: center">0.83, 0.81, 0.78</td><td style="text-align: center">#d3cec6</td><td><div style="background-color: #d6d1c8; width: 60px"> </div></td></tr>
<tr><td style="text-align: right">Gold</td><td style="text-align: center">1.00, 0.85, 0.57</td><td style="text-align: center">#ffd891</td><td><div style="background-color: #fedc9d; width: 60px"> </div></td></tr>
<tr><td style="text-align: right">Brass</td><td style="text-align: center">0.98, 0.90, 0.59</td><td style="text-align: center">#f9e596</td><td><div style="background-color: #f4e4ad; width: 60px"> </div></td></tr>
<tr><td style="text-align: right">Copper</td><td style="text-align: center">0.97, 0.74, 0.62</td><td style="text-align: center">#f7bc9e</td><td><div style="background-color: #fbd8b8; width: 60px"> </div></td></tr>
</tbody></table>
</div>
<p>[Table [baseColorsConductors]: <code>baseColor</code> for common metals]</p>
<h3 id="metallic"><a class="header" href="#metallic">Metallic</a></h3>
<p>The <code>metallic</code> property defines whether the surface is a metallic (<em>conductor</em>)
or a non-metallic (<em>dielectric</em>) surface. This property should be used as a
binary value, set to either 0 or 1. Intermediate values are only truly useful to
create transitions between different types of surfaces when using textures.</p>
<p>This property can dramatically change the appearance of a surface. Non-metallic
surfaces have chromatic diffuse reflection and achromatic specular reflection
(reflected light does not change color). Metallic surfaces do not have any
diffuse reflection and chromatic specular reflection (reflected light takes on
the color of the surfaced as defined by <code>baseColor</code>).</p>
<p>The effect of <code>metallic</code> is shown in figure
[metallicProperty](click on the image to see a larger version).</p>
<p><img src="images/materials/metallic.png" alt="Figure [metallicProperty]: metallic varying from 0.0 (left) to 1.0 (right)" /></p>
<h3 id="roughness"><a class="header" href="#roughness">Roughness</a></h3>
<p>The <code>roughness</code> property controls the perceived smoothness of the surface. When
<code>roughness</code> is set to 0, the surface is perfectly smooth and highly glossy. The
rougher a surface is, the &quot;blurrier&quot; the reflections are. This property is often
called <em>glossiness</em> in other engines and tools, and is simply the opposite of
the roughness (<code>roughness = 1 - glossiness</code>).</p>
<h3 id="non-metals"><a class="header" href="#non-metals">Non-metals</a></h3>
<p>The effect of <code>roughness</code> on non-metallic surfaces is shown in figure
[roughnessProperty](click on the image to see a larger version).</p>
<p><img src="images/materials/dielectric_roughness.png" alt="Figure [roughnessProperty]: Dielectric roughness varying from 0.0 (left) to 1.0 (right)" /></p>
<h3 id="metals"><a class="header" href="#metals">Metals</a></h3>
<p>The effect of <code>roughness</code> on metallic surfaces is shown in figure
[roughnessConductorProperty](click on the image to see a larger version).</p>
<p><img src="images/materials/conductor_roughness.png" alt="Figure [roughnessConductorProperty]: Conductor roughness varying from 0.0 (left) to 1.0 (right)" /></p>
<h3 id="refraction"><a class="header" href="#refraction">Refraction</a></h3>
<p>When refraction through an object is enabled (using a <code>refractonType</code> of <code>thin</code>
or <code>solid</code>), the <code>roughness</code> property will also affect the refractions, as shown
in figure
[roughnessRefractionProperty](click on the image to see a larger version).</p>
<p><img src="images/materials/refraction_roughness.png" alt="Figure [roughnessRefractionProperty]: Refractive sphere with roughness varying from 0.0 (left) to 1.0 (right)" /></p>
<h3 id="reflectance"><a class="header" href="#reflectance">Reflectance</a></h3>
<p>The <code>reflectance</code> property only affects non-metallic surfaces. This property can
be used to control the specular intensity and index of refraction of materials.
This value is defined between 0 and 1 and represents a remapping of a percentage
of reflectance. For instance, the default value of 0.5 corresponds to a
reflectance of 4%. Values below 0.35 (2% reflectance) should be avoided as no
real-world materials have such low reflectance.</p>
<p>The effect of <code>reflectance</code> on non-metallic surfaces is shown in figure
[reflectanceProperty](click on the image to see a larger version).</p>
<p><img src="images/materials/reflectance.png" alt="Figure [reflectanceProperty]: reflectance varying from 0.0 (left) to 1.0 (right)" /></p>
<p>Figure [reflectance] shows common values and how they relate to the mapping
function.</p>
<p><img src="images/diagram_reflectance.png" alt="Figure [reflectance]: Common reflectance values" /></p>
<p>Table [commonMatReflectance] describes acceptable reflectance values for various
types of materials (no real world material has a value under 2%).</p>
<div class="table-wrapper"><table><thead><tr><th style="text-align: right">Material</th><th style="text-align: left">Reflectance</th><th style="text-align: left">IOR</th><th style="text-align: left">Linear value</th></tr></thead><tbody>
<tr><td style="text-align: right">Water</td><td style="text-align: left">2%</td><td style="text-align: left">1.33</td><td style="text-align: left">0.35</td></tr>
<tr><td style="text-align: right">Fabric</td><td style="text-align: left">4% to 5.6%</td><td style="text-align: left">1.5 to 1.62</td><td style="text-align: left">0.5 to 0.59</td></tr>
<tr><td style="text-align: right">Common liquids</td><td style="text-align: left">2% to 4%</td><td style="text-align: left">1.33 to 1.5</td><td style="text-align: left">0.35 to 0.5</td></tr>
<tr><td style="text-align: right">Common gemstones</td><td style="text-align: left">5% to 16%</td><td style="text-align: left">1.58 to 2.33</td><td style="text-align: left">0.56 to 1.0</td></tr>
<tr><td style="text-align: right">Plastics, glass</td><td style="text-align: left">4% to 5%</td><td style="text-align: left">1.5 to 1.58</td><td style="text-align: left">0.5 to 0.56</td></tr>
<tr><td style="text-align: right">Other dielectric materials</td><td style="text-align: left">2% to 5%</td><td style="text-align: left">1.33 to 1.58</td><td style="text-align: left">0.35 to 0.56</td></tr>
<tr><td style="text-align: right">Eyes</td><td style="text-align: left">2.5%</td><td style="text-align: left">1.38</td><td style="text-align: left">0.39</td></tr>
<tr><td style="text-align: right">Skin</td><td style="text-align: left">2.8%</td><td style="text-align: left">1.4</td><td style="text-align: left">0.42</td></tr>
<tr><td style="text-align: right">Hair</td><td style="text-align: left">4.6%</td><td style="text-align: left">1.55</td><td style="text-align: left">0.54</td></tr>
<tr><td style="text-align: right">Teeth</td><td style="text-align: left">5.8%</td><td style="text-align: left">1.63</td><td style="text-align: left">0.6</td></tr>
<tr><td style="text-align: right">Default value</td><td style="text-align: left">4%</td><td style="text-align: left">1.5</td><td style="text-align: left">0.5</td></tr>
</tbody></table>
</div>
<p>[Table [commonMatReflectance]: Reflectance of common materials]</p>
<p>Note that the <code>reflectance</code> property also defines the index of refraction of the
surface. When this property is defined it is not necessary to define the <code>ior</code>
property. Setting either of these properties will automatically compute the
other property. It is possible to specify both, in which case their values are
kept as-is, which can lead to physically impossible materials, however, this
might be desirable for artistic reasons.</p>
<p>The <code>reflectance</code> property is designed as a normalized property in the range
0..1 which makes it easy to define from a texture.</p>
<p>See section [Index of refraction] for more information about the <code>ior</code> property
and refractive indices.</p>
<h3 id="sheen-color"><a class="header" href="#sheen-color">Sheen color</a></h3>
<p>The sheen color controls the color appearance and strength of an optional sheen
layer on top of the base layer described by the properties above. The sheen
layer always sits below the clear coat layer if such a layer is present.</p>
<p>The sheen layer can be used to represent cloth and fabric materials. Please
refer to section [Cloth model] for more information about cloth and fabric
materials.</p>
<p>The effect of <code>sheenColor</code> is shown in figure
[materialSheenColor](click on the image to see a larger version).</p>
<p><img src="images/screenshot_sheen_color.png" alt="Figure [materialSheenColor]: Different sheen colors" /></p>
<p>!!! Note If you do not need the other properties offered by the standard lit
material model but want to create a cloth-like or fabric-like appearance, it is
more efficient to use the dedicated cloth model described in section [Cloth
model].</p>
<h3 id="sheen-roughness"><a class="header" href="#sheen-roughness">Sheen roughness</a></h3>
<p>The <code>sheenRoughness</code> property is similar to the <code>roughness</code> property but applies
only to the sheen layer.</p>
<p>The effect of <code>sheenRoughness</code> on a rough metal is shown in figure
[sheenRoughnessProperty](click on the image to see a larger version). In this
picture, the base layer is a dark blue, with <code>metallic</code> set to <code>0.0</code> and
<code>roughness</code> set to <code>1.0</code>.</p>
<p><img src="images/materials/sheen_roughness.png" alt="Figure [sheenRoughnessProperty]: sheenRoughness varying from 0.0 (left) to 1.0 (right)" /></p>
<h3 id="clear-coat"><a class="header" href="#clear-coat">Clear coat</a></h3>
<p>Multi-layer materials are fairly common, particularly materials with a thin
translucent layer over a base layer. Real world examples of such materials
include car paints, soda cans, lacquered wood and acrylic.</p>
<p>The <code>clearCoat</code> property can be used to describe materials with two layers. The
clear coat layer will always be isotropic and dielectric.</p>
<p><img src="images/material_carbon_fiber.png" alt="Figure [clearCoat]: Comparison of a carbon-fiber material under the standard material model (left) and the clear coat model (right)" /></p>
<p>The <code>clearCoat</code> property controls the strength of the clear coat layer. This
should be treated as a binary value, set to either 0 or 1. Intermediate values
are useful to control transitions between parts of the surface that have a clear
coat layers and parts that don't.</p>
<p>The effect of <code>clearCoat</code> on a rough metal is shown in figure
[clearCoatProperty](click on the image to see a larger version).</p>
<p><img src="images/materials/clear_coat.png" alt="Figure [clearCoatProperty]: clearCoat varying from 0.0 (left) to 1.0 (right)" /></p>
<p>!!! Warning The clear coat layer effectively doubles the cost of specular
computations. Do not assign a value, even 0.0, to the clear coat property if you
don't need this second layer.</p>
<p>!!! Note The clear coat layer is added on top of the sheen layer if present.</p>
<h3 id="clear-coat-roughness"><a class="header" href="#clear-coat-roughness">Clear coat roughness</a></h3>
<p>The <code>clearCoatRoughness</code> property is similar to the <code>roughness</code> property but
applies only to the clear coat layer.</p>
<p>The effect of <code>clearCoatRoughness</code> on a rough metal is shown in figure
[clearCoatRoughnessProperty](click on the image to see a larger version).</p>
<p><img src="images/materials/clear_coat_roughness.png" alt="Figure [clearCoatRoughnessProperty]: clearCoatRoughness varying from 0.0 (left) to 1.0 (right)" /></p>
<h3 id="anisotropy"><a class="header" href="#anisotropy">Anisotropy</a></h3>
<p>Many real-world materials, such as brushed metal, can only be replicated using
an anisotropic reflectance model. A material can be changed from the default
isotropic model to an anisotropic model by using the <code>anisotropy</code> property.</p>
<p><img src="images/material_anisotropic.png" alt="Figure [anisotropic]: Comparison of isotropic material (left) and anistropic material (right)" /></p>
<p>The effect of <code>anisotropy</code> on a rough metal is shown in figure
[anisotropyProperty](click on the image to see a larger version).</p>
<p><img src="images/materials/anisotropy.png" alt="Figure [anisotropyProperty]: anisotropy varying from 0.0 (left) to 1.0 (right)" /></p>
<p>The figure [anisotropyDir] below shows how the direction of the anisotropic
highlights can be controlled by using either positive or negative values:
positive values define anisotropy in the tangent direction and negative values
in the bitangent direction.</p>
<p><img src="images/screenshot_anisotropy_direction.png" alt="Figure [anisotropyDir]: Positive (left) vs negative (right) anisotropy values" /></p>
<p>!!! Tip The anisotropic material model is slightly more expensive than the
standard material model. Do not assign a value (even 0.0) to the <code>anisotropy</code>
property if you don't need anisotropy.</p>
<h3 id="anisotropy-direction"><a class="header" href="#anisotropy-direction">Anisotropy direction</a></h3>
<p>The <code>anisotropyDirection</code> property defines the direction of the surface at a
given point and thus control the shape of the specular highlights. It is
specified as vector of 3 values that usually come from a texture, encoding the
directions local to the surface in tangent space. Because the direction is in
tangent space, the Z component should be set to 0.</p>
<p>The effect of <code>anisotropyDirection</code> on a metal is shown in figure
[anisotropyDirectionProperty](click on the image to see a larger version).</p>
<p><img src="images/screenshot_anisotropy.png" alt="Figure [anisotropyDirectionProperty]: Anisotropic metal rendered with a direction map" /></p>
<p>The result shown in figure [anisotropyDirectionProperty] was obtained using the
direction map shown in figure [anisotropyDirectionProperty].</p>
<p><img src="images/screenshot_anisotropy_map.jpg" alt="Figure [anisotropyDirectionProperty]: Example of Lighting: specularAmbientOcclusiona direction map" /></p>
<h3 id="ambient-occlusion"><a class="header" href="#ambient-occlusion">Ambient occlusion</a></h3>
<p>The <code>ambientOcclusion</code> property defines how much of the ambient light is
accessible to a surface point. It is a per-pixel shadowing factor between 0.0
(fully shadowed) and 1.0 (fully lit). This property only affects diffuse
indirect lighting (image-based lighting), not direct lights such as directional,
point and spot lights, nor specular lighting.</p>
<p><img src="images/screenshot_ao.jpg" alt="Figure [aoExample]: Comparison of materials without diffuse ambient occlusion (left) and with (right)" /></p>
<h3 id="normal"><a class="header" href="#normal">Normal</a></h3>
<p>The <code>normal</code> property defines the normal of the surface at a given point. It
usually comes from a <em>normal map</em> texture, which allows to vary the property
per-pixel. The normal is supplied in tangent space, which means that +Z points
outside of the surface.</p>
<p>For example, let's imagine that we want to render a piece of furniture covered
in tufted leather. Modeling the geometry to accurately represent the tufted
pattern would require too many triangles so we instead bake a high-poly mesh
into a normal map. Once the base map is applied to a simplified mesh, we get the
result in figure [normalMapped].</p>
<p>Note that the <code>normal</code> property affects the <em>base layer</em> and not the clear coat
layer.</p>
<p><img src="images/screenshot_normal_mapping.jpg" alt="Figure [normalMapped]: Low-poly mesh without normal mapping (left) and with (right)" /></p>
<p>!!! Warning Using a normal map increases the runtime cost of the material model.</p>
<h3 id="bent-normal"><a class="header" href="#bent-normal">Bent normal</a></h3>
<p>The <code>bentNormal</code> property defines the average unoccluded direction at a point on
the surface. It is used to improve the accuracy of indirect lighting. Bent
normals can also improve the quality of specular ambient occlusion (see section
[Lighting: specularAmbientOcclusion] about <code>specularAmbientOcclusion</code>).</p>
<p>Bent normals can greatly increase the visual fidelity of an asset with various
cavities and concave areas, as shown in figure [bentNormalMapped]. See the areas
of the ears, nostrils and eyes for instance.</p>
<p><img src="images/material_bent_normal.gif" alt="Figure [bentNormalMapped]: Example of a model rendered with and without a bent normal map. Both versions use the same ambient occlusion map." /></p>
<h3 id="clear-coat-normal"><a class="header" href="#clear-coat-normal">Clear coat normal</a></h3>
<p>The <code>clearCoatNormal</code> property defines the normal of the clear coat layer at a
given point. It behaves otherwise like the <code>normal</code> property.</p>
<p><img src="images/screenshot_clear_coat_normal.jpg" alt="Figure [clearCoatNormalMapped]: A material with a clear coat normal map and a surface normal map" /></p>
<p>!!! Warning Using a clear coat normal map increases the runtime cost of the
material model.</p>
<h3 id="emissive"><a class="header" href="#emissive">Emissive</a></h3>
<p>The <code>emissive</code> property can be used to simulate additional light emitted by the
surface. It is defined as a <code>float4</code> value that contains an RGB intensity in
nits as well as an exposure weight (in the alpha channel).</p>
<p>The intensity in nits allows an emissive surface to function as a light and can
be used to recreate real world surfaces. For instance a computer display has an
intensity between 200 and 1,000 nits.</p>
<p>If you prefer to work in EV (or f-stops), you can simplify multiply your
emissive color by the output of the API <code>filament::Exposure::luminance(ev)</code>.
This API returns the luminance in nits of the specific EV. You can perform this
conversion yourself using the following formula, where \(L\) is the final
intensity in nits: \( L = 2^{EV - 3} \).</p>
<p>The exposure weight carried in the alpha channel can be used to undo the camera
exposure, and thus force an emissive surface to bloom. When the exposure weight
is set to 0, the emissive intensity is not affected by the camera exposure. When
the weight is set to 1, the intensity is multiplied by the camera exposure like
with any regular light.</p>
<h3 id="post-lighting-color"><a class="header" href="#post-lighting-color">Post-lighting color</a></h3>
<p>The <code>postLightingColor</code> can be used to modify the surface color after lighting
computations. This property has no physical meaning and only exists to implement
specific effects or to help with debugging. This property is defined as a
<code>float4</code> value containing a pre-multiplied RGB color in linear space.</p>
<p>The post-lighting color is blended with the result of lighting according to the
blending mode specified by the <code>postLightingBlending</code> material option. Please
refer to the documentation of this option for more information.</p>
<p>!!! Tip <code>postLightingColor</code> can be used as a simpler <code>emissive</code> property by
setting <code>postLightingBlending</code> to <code>add</code> and by providing an RGB color with alpha
set to <code>0.0</code>.</p>
<h3 id="index-of-refraction"><a class="header" href="#index-of-refraction">Index of refraction</a></h3>
<p>The <code>ior</code> property only affects non-metallic surfaces. This property can be used
to control the index of refraction and the specular intensity of materials. The
<code>ior</code> property is intended to be used with refractive (transmissive) materials,
which are enabled when the <code>refractionMode</code> is set to <code>cubemap</code> or
<code>screenspace</code>. It can also be used on non-refractive objects as an alternative
to setting the reflectance.</p>
<p>The index of refraction (or refractive index) of a material is a dimensionless
number that describes how fast light travels through that material. The higher
the number, the slower light travels through the medium. More importantly for
rendering materials, the refractive index determines how the path light travels
is bent when entering the material. Higher indices of refraction will cause
light to bend further away from the initial path.</p>
<p>Table [commonMatIOR] describes acceptable refractive indices for various types
of materials.</p>
<div class="table-wrapper"><table><thead><tr><th style="text-align: right">Material</th><th style="text-align: left">IOR</th></tr></thead><tbody>
<tr><td style="text-align: right">Air</td><td style="text-align: left">1.0</td></tr>
<tr><td style="text-align: right">Water</td><td style="text-align: left">1.33</td></tr>
<tr><td style="text-align: right">Common liquids</td><td style="text-align: left">1.33 to 1.5</td></tr>
<tr><td style="text-align: right">Common gemstones</td><td style="text-align: left">1.58 to 2.33</td></tr>
<tr><td style="text-align: right">Plastics, glass</td><td style="text-align: left">1.5 to 1.58</td></tr>
<tr><td style="text-align: right">Other dielectric materials</td><td style="text-align: left">1.33 to 1.58</td></tr>
</tbody></table>
</div>
<p>[Table [commonMatIOR]: Index of refraction of common materials]</p>
<p>The appearance of a refractive material will greatly depend on the
<code>refractionType</code> and <code>refractionMode</code> settings of the material. Refer to section
[Blending and transparency: refractionType] and section [Blending and
transparency: refractionMode] for more information.</p>
<p>The effect of <code>ior</code> when <code>refractionMode</code> is set to <code>cubemap</code> and
<code>refractionType</code> is set to <code>solid</code> can be seen in figure
[iorProperty2](click on the image to see a larger version).</p>
<p><img src="images/materials/ior.png" alt="Figure [iorProperty2]: transmission varying from 1.0 (left) to 1.5 (right)" /></p>
<p>Figure [iorProperty] shows the comparison of a sphere of <code>ior</code> 1.0 with a sphere
of <code>ior</code> 1.33, with the <code>refractionMode</code> set to <code>screenspace</code> and the
<code>refractionType</code> set to <code>solid</code> (click on the image to see a larger version).</p>
<p><img src="images/material_ior.png" alt="Figure [iorProperty]: ior of 1.0 (left) and 1.33 (right)" /></p>
<p>Note that the <code>ior</code> property also defines the reflectance (or specular
intensity) of the surface. When this property is defined it is not necessary to
define the <code>reflectance</code> property. Setting either of these properties will
automatically compute the other property. It is possible to specify both, in
which case their values are kept as-is, which can lead to physically impossible
materials, however, this might be desirable for artistic reasons.</p>
<p>See the Reflectance section for more information on the <code>reflectance</code> property.</p>
<p>!!! Tip Refractive materials are affected by the <code>roughness</code> property. Rough
materials will scatter light, creating a diffusion effect useful to recreate
&quot;blurry&quot; appearances such as frosted glass, certain plastics, etc.</p>
<h3 id="transmission"><a class="header" href="#transmission">Transmission</a></h3>
<p>The <code>transmission</code> property defines what ratio of diffuse light is transmitted
through a refractive material. This property only affects materials with a
<code>refractionMode</code> set to <code>cubemap</code> or <code>screenspace</code>.</p>
<p>When <code>transmission</code> is set to 0, no amount of light is transmitted and the
diffuse component of the surface is 100% visible. When <code>transmission</code> is set to
1, all the light is transmitted and the diffuse component is not visible
anymore, only the specular component is.</p>
<p>The effect of <code>transmission</code> on a glossy dielectric (<code>ior</code> of 1.5,
<code>refractionMode</code> set to <code>cubemap</code>, <code>refractionType</code> set to <code>solid</code>) is shown in
figure [transmissionProperty](click on the image to see a larger version).</p>
<p><img src="images/materials/transmission.png" alt="Figure [transmissionProperty]: transmission varying from 0.0 (left) to 1.0 (right)" /></p>
<p>!!! Tip The <code>transmission</code> property is useful to create decals, paint, etc. at
the surface of refractive materials.</p>
<h3 id="absorption"><a class="header" href="#absorption">Absorption</a></h3>
<p>The <code>absorption</code> property defines the absorption coefficients of light
transmitted through the material. Figure [absorptionExample] shows the effect of
<code>absorption</code> on a refracting object with an index of refraction of 1.5 and a
base color set to white.</p>
<p><img src="images/material_absorption.png" alt="Figure [absorptionExample]: Refracting object without (left) and with (right) absorption" /></p>
<p>Transmittance through a volume is exponential with respect to the optical depth
(defined either with <code>microThickness</code> or <code>thickness</code>). The computed color
follows the following formula:</p>
<p>$$color \cdot e^{-absorption \cdot distance}$$</p>
<p>Where <code>distance</code> is either <code>microThickness</code> or <code>thickness</code>, that is the distance
light will travel through the material at a given point. If no
thickness/distance is specified, the computed color follows this formula
instead:</p>
<p>$$color \cdot (1 - absorption)$$</p>
<p>The effect of varying the <code>absorption</code> coefficients is shown in figure
[absorptionProperty](click on the image to see a larger version). In this
picture, the object has a fixed <code>thickness</code> of 4.5 and an index of refraction
set to 1.3.</p>
<p><img src="images/materials/absorption.png" alt="Figure [absorptionProperty]: absorption varying from (0.0, 0.02, 0.14) (left) to (0.0, 0.36, 2.3) (right)" /></p>
<p>Setting the absorption coefficients directly can be unintuitive which is why we
recommend working with a <em>transmittance color</em> and a <em>&quot;at distance&quot;</em> factor
instead. These two parameters allow an artist to specify the precise color the
material should have at a specified distance through the volume. The value to
pass to <code>absorption</code> can be computed this way:</p>
<p>$$absorption = -\frac{ln(transmittanceColor)}{atDistance}$$</p>
<p>While this computation can be done in the material itself we recommend doing it
offline whenever possible. Filament provides an API for this purpose,
<code>Color::absorptionAtDistance()</code>.</p>
<h3 id="micro-thickness-and-thickness"><a class="header" href="#micro-thickness-and-thickness">Micro-thickness and thickness</a></h3>
<p>The <code>microThickness</code> and <code>thickness</code> properties define the optical depth of the
material of a refracting object. <code>microThickness</code> is used when <code>refractionType</code>
is set to <code>thin</code>, and <code>thickness</code> is used when <code>refractionType</code> is set to
<code>volume</code>.</p>
<p><code>thickness</code> represents the thickness of solid objects in the direction of the
normal, for satisfactory results, this should be provided per fragment (e.g.: as
a texture) or at least per vertex.</p>
<p><code>microThickness</code> represent the thickness of the thin layer (shell) of an object,
and can generally be provided as a constant value. For example, a 1mm thin
hollow sphere of radius 1m, would have a <code>thickness</code> of 1 and a <code>microThickness</code>
of 0.001. Currently <code>thickness</code> is not used when <code>refractionType</code> is set to
<code>thin</code>. Both properties are made available for possible future use.</p>
<p>Both <code>thickness</code> and <code>microThickness</code> are used to compute the transmitted color
of the material when the <code>absorption</code> property is set. In solid volumes,
<code>thickness</code> will also affect how light rays are refracted.</p>
<p>The effect <code>thickness</code> in a solid volume with <code>refractionMode</code> set to
<code>screenSpace</code> is shown in figure
[thicknessProperty](click on the image to see a larger version). Note how the
<code>thickness</code> value not only changes the effect of <code>absorption</code> but also modifies
the direction of the refracted light.</p>
<p><img src="images/materials/thickness.png" alt="Figure [thicknessProperty]: thickness varying from 0.0 (left) to 2.0 (right)" /></p>
<p>Figure [varyingThickness] shows what a prism with spatially varying <code>thickness</code>
looks like when the <code>refractionType</code> is set to <code>solid</code> and <code>absorption</code>
coefficients are set.</p>
<p><img src="images/material_thickness.png" alt="Figure [varyingThickness]: thickness varying from 0.0 at the top of the prism to 3.0 at the bottom of the prism" /></p>
<h2 id="subsurface-model"><a class="header" href="#subsurface-model">Subsurface model</a></h2>
<h3 id="thickness"><a class="header" href="#thickness">Thickness</a></h3>
<h3 id="subsurface-color"><a class="header" href="#subsurface-color">Subsurface color</a></h3>
<h3 id="subsurface-power"><a class="header" href="#subsurface-power">Subsurface power</a></h3>
<h2 id="cloth-model"><a class="header" href="#cloth-model">Cloth model</a></h2>
<p>All the material models described previously are designed to simulate dense
surfaces, both at a macro and at a micro level. Clothes and fabrics are however
often made of loosely connected threads that absorb and scatter incident light.
When compared to hard surfaces, cloth is characterized by a softer specular lob
with a large falloff and the presence of fuzz lighting, caused by
forward/backward scattering. Some fabrics also exhibit two-tone specular colors
(velvets for instance).</p>
<p>Figure [materialCloth] shows how the standard material model fails to capture
the appearance of a sample of denim fabric. The surface appears rigid (almost
plastic-like), more similar to a tarp than a piece of clothing. This figure also
shows how important the softer specular lobe caused by absorption and scattering
is to the faithful recreation of the fabric.</p>
<p><img src="images/screenshot_cloth.png" alt="Figure [materialCloth]: Comparison of denim fabric rendered using the standard model (left) and the cloth model (right)" /></p>
<p>Velvet is an interesting use case for a cloth material model. As shown in figure
[materialVelvet] this type of fabric exhibits strong rim lighting due to forward
and backward scattering. These scattering events are caused by fibers standing
straight at the surface of the fabric. When the incident light comes from the
direction opposite to the view direction, the fibers will forward scatter the
light. Similarly, when the incident light from the same direction as the view
direction, the fibers will scatter the light backward.</p>
<p><img src="images/screenshot_cloth_velvet.png" alt="Figure [materialVelvet]: Velvet fabric showcasing forward and backward scattering" /></p>
<p>It is important to note that there are types of fabrics that are still best
modeled by hard surface material models. For instance, leather, silk and satin
can be recreated using the standard or anisotropic material models.</p>
<p>The cloth material model encompasses all the parameters previously defined for
the standard material mode except for <em>metallic</em> and <em>reflectance</em>. Two extra
parameters described in table [clothProperties] are also available.</p>
<div class="table-wrapper"><table><thead><tr><th style="text-align: right">Parameter</th><th style="text-align: left">Definition</th></tr></thead><tbody>
<tr><td style="text-align: right"><strong>sheenColor</strong></td><td style="text-align: left">Specular tint to create two-tone specular fabrics (defaults to \(\sqrt{baseColor}\))</td></tr>
<tr><td style="text-align: right"><strong>subsurfaceColor</strong></td><td style="text-align: left">Tint for the diffuse color after scattering and absorption through the material</td></tr>
</tbody></table>
</div>
<p>[Table [clothProperties]: Cloth model parameters]</p>
<p>The type and range of each property is described in table
[clothPropertiesTypes].</p>
<div class="table-wrapper"><table><thead><tr><th style="text-align: right">Property</th><th style="text-align: center">Type</th><th style="text-align: center">Range</th><th style="text-align: left">Note</th></tr></thead><tbody>
<tr><td style="text-align: right"><strong>sheenColor</strong></td><td style="text-align: center">float3</td><td style="text-align: center">[0..1]</td><td style="text-align: left">Linear RGB</td></tr>
<tr><td style="text-align: right"><strong>subsurfaceColor</strong></td><td style="text-align: center">float3</td><td style="text-align: center">[0..1]</td><td style="text-align: left">Linear RGB</td></tr>
</tbody></table>
</div>
<p>[Table [clothPropertiesTypes]: Range and type of the cloth model's properties]</p>
<p>To create a velvet-like material, the base color can be set to black (or a dark
color). Chromaticity information should instead be set on the sheen color. To
create more common fabrics such as denim, cotton, etc. use the base color for
chromaticity and use the default sheen color or set the sheen color to the
luminance of the base color.</p>
<p>!!! Tip To see the effect of the <code>roughness</code> parameter make sure the
<code>sheenColor</code> is brighter than <code>baseColor</code>. This can be used to create a fuzz
effect. Taking the luminance of <code>baseColor</code> as the <code>sheenColor</code> will produce a
fairly natural effect that works for common cloth. A dark <code>baseColor</code> combined
with a bright/saturated <code>sheenColor</code> can be used to create velvet.</p>
<p>!!! Tip The <code>subsurfaceColor</code> parameter should be used with care. High values
can interfere with shadows in some areas. It is best suited for subtle
transmission effects through the material.</p>
<h3 id="sheen-color-1"><a class="header" href="#sheen-color-1">Sheen color</a></h3>
<p>The <code>sheenColor</code> property can be used to directly modify the specular
reflectance. It offers better control over the appearance of cloth and gives
give the ability to create two-tone specular materials.</p>
<p>The effect of <code>sheenColor</code> is shown in figure
[materialClothSheen](click on the image to see a larger version).</p>
<p><img src="images/screenshot_cloth_sheen.png" alt="Figure [materialClothSheen]: Blue fabric without (left) and with (right) sheen" /></p>
<h3 id="subsurface-color-1"><a class="header" href="#subsurface-color-1">Subsurface color</a></h3>
<p>The <code>subsurfaceColor</code> property is not physically-based and can be used to
simulate the scattering, partial absorption and re-emission of light in certain
types of fabrics. This is particularly useful to create softer fabrics.</p>
<p>!!! Warning The cloth material model is more expensive to compute when the
<code>subsurfaceColor</code> property is used.</p>
<p>The effect of <code>subsurfaceColor</code> is shown in figure
[materialClothSubsurface](click on the image to see a larger version).</p>
<p><img src="images/screenshot_cloth_subsurface.png" alt="Figure [materialClothSubsurface]: White cloth (left column) vs white cloth with brown subsurface scatting (right)" /></p>
<h2 id="unlit-model"><a class="header" href="#unlit-model">Unlit model</a></h2>
<p>The unlit material model can be used to turn off all lighting computations. Its
primary purpose is to render pre-lit elements such as a cubemap, external
content (such as a video or camera stream), user interfaces,
visualization/debugging etc. The unlit model exposes only two properties
described in table [unlitProperties].</p>
<div class="table-wrapper"><table><thead><tr><th style="text-align: right">Property</th><th style="text-align: left">Definition</th></tr></thead><tbody>
<tr><td style="text-align: right"><strong>baseColor</strong></td><td style="text-align: left">Surface diffuse color</td></tr>
<tr><td style="text-align: right"><strong>emissive</strong></td><td style="text-align: left">Additional diffuse color to simulate emissive surfaces. This property is mostly useful in an HDR pipeline with a bloom pass</td></tr>
<tr><td style="text-align: right"><strong>postLightingColor</strong></td><td style="text-align: left">Additional color to blend with base color and emissive</td></tr>
</tbody></table>
</div>
<p>[Table [unlitProperties]: Properties of the standard model]</p>
<p>The type and range of each property is described in table
[unlitPropertiesTypes].</p>
<div class="table-wrapper"><table><thead><tr><th style="text-align: right">Property</th><th style="text-align: center">Type</th><th style="text-align: center">Range</th><th style="text-align: left">Note</th></tr></thead><tbody>
<tr><td style="text-align: right"><strong>baseColor</strong></td><td style="text-align: center">float4</td><td style="text-align: center">[0..1]</td><td style="text-align: left">Pre-multiplied linear RGB</td></tr>
<tr><td style="text-align: right"><strong>emissive</strong></td><td style="text-align: center">float4</td><td style="text-align: center">rgb=[0..n], a=[0..1]</td><td style="text-align: left">Linear RGB intensity in nits, alpha encodes the exposure weight</td></tr>
<tr><td style="text-align: right"><strong>postLightingColor</strong></td><td style="text-align: center">float4</td><td style="text-align: center">[0..1]</td><td style="text-align: left">Pre-multiplied linear RGB</td></tr>
</tbody></table>
</div>
<p>[Table [unlitPropertiesTypes]: Range and type of the unlit model's properties]</p>
<p>The value of <code>postLightingColor</code> is blended with the sum of <code>emissive</code> and
<code>baseColor</code> according to the blending mode specified by the
<code>postLightingBlending</code> material option.</p>
<p>Figure [materialUnlit] shows an example of the unlit material model (click on
the image to see a larger version).</p>
<p><img src="images/screenshot_unlit.jpg" alt="Figure [materialUnlit]: The unlit model is used to render debug information" /></p>
<h2 id="specular-glossiness"><a class="header" href="#specular-glossiness">Specular glossiness</a></h2>
<p>This alternative lighting model exists to comply with legacy standards. Since it
is not a physically-based formulation, we do not recommend using it except when
loading legacy assets.</p>
<p>This model encompasses the parameters previously defined for the standard lit
mode except for <em>metallic</em>, <em>reflectance</em>, and <em>roughness</em>. It adds parameters
for <em>specularColor</em> and <em>glossiness</em>.</p>
<div class="table-wrapper"><table><thead><tr><th style="text-align: right">Parameter</th><th style="text-align: left">Definition</th></tr></thead><tbody>
<tr><td style="text-align: right"><strong>baseColor</strong></td><td style="text-align: left">Surface diffuse color</td></tr>
<tr><td style="text-align: right"><strong>specularColor</strong></td><td style="text-align: left">Specular tint (defaults to black)</td></tr>
<tr><td style="text-align: right"><strong>glossiness</strong></td><td style="text-align: left">Glossiness (defaults to 0.0)</td></tr>
</tbody></table>
</div>
<p>[Table [glossinessProperties]: Properties of the specular-glossiness shading
model]</p>
<p>The type and range of each property is described in table
[glossinessPropertiesTypes].</p>
<div class="table-wrapper"><table><thead><tr><th style="text-align: right">Property</th><th style="text-align: center">Type</th><th style="text-align: center">Range</th><th style="text-align: left">Note</th></tr></thead><tbody>
<tr><td style="text-align: right"><strong>baseColor</strong></td><td style="text-align: center">float4</td><td style="text-align: center">[0..1]</td><td style="text-align: left">Pre-multiplied linear RGB</td></tr>
<tr><td style="text-align: right"><strong>specularColor</strong></td><td style="text-align: center">float3</td><td style="text-align: center">[0..1]</td><td style="text-align: left">Linear RGB</td></tr>
<tr><td style="text-align: right"><strong>glossiness</strong></td><td style="text-align: center">float</td><td style="text-align: center">[0..1]</td><td style="text-align: left">Inverse of roughness</td></tr>
</tbody></table>
</div>
<p>[Table [glossinessPropertiesTypes]: Range and type of the specular-glossiness
model's properties]</p>
<h1 id="material-definitions"><a class="header" href="#material-definitions">Material definitions</a></h1>
<p>A material definition is a text file that describes all the information required
by a material:</p>
<ul>
<li>Name</li>
<li>User parameters</li>
<li>Material model</li>
<li>Required attributes</li>
<li>Interpolants (called <em>variables</em>)</li>
<li>Raster state (blending mode, etc.)</li>
<li>Shader code (fragment shader, optionally vertex shader)</li>
</ul>
<h2 id="format"><a class="header" href="#format">Format</a></h2>
<p>The material definition format is a format loosely based on
<a href="https://www.json.org/">JSON</a> that we call <em>JSONish</em>. At the top level a
material definition is composed of 3 different blocks that use the JSON object
notation:</p>
<pre><code class="language-json">material {
// material properties
}
vertex {
// vertex shader, optional
}
fragment {
// fragment shader
}
</code></pre>
<p>A minimum viable material definition must contain a <code>material</code> preamble and a
<code>fragment</code> block. The <code>vertex</code> block is optional.</p>
<h3 id="differences-with-json"><a class="header" href="#differences-with-json">Differences with JSON</a></h3>
<p>In JSON, an object is made of key/value <em>pairs</em>. A JSON pair has the following
syntax:</p>
<pre><code class="language-json">&quot;key&quot; : value
</code></pre>
<p>Where value can be a string, number, object, array or a literal (<code>true</code>, <code>false</code>
or <code>null</code>). While this syntax is perfectly valid in a material definition, a
variant without quotes around strings is also accepted in JSONish:</p>
<pre><code class="language-json">key : value
</code></pre>
<p>Quotes remain mandatory when the string contains spaces.</p>
<p>The <code>vertex</code> and <code>fragment</code> blocks contain unescaped, unquoted GLSL code, which
is not valid in JSON.</p>
<p>Single-line C++-style comments are allowed.</p>
<p>The key of a pair is case-sensitive.</p>
<p>The value of a pair is not case-sensitive.</p>
<h3 id="example"><a class="header" href="#example">Example</a></h3>
<p>The following code listing shows an example of a valid material definition. This
definition uses the <em>lit</em> material model (see Lit model section), uses the
default opaque blending mode, requires that a set of UV coordinates be presented
in the rendered mesh and defines 3 user parameters. The following sections of
this document describe the <code>material</code> and <code>fragment</code> blocks in detail.</p>
<pre><code class="language-json">material {
name : &quot;Textured material&quot;,
parameters : [
{
type : sampler2d,
name : texture
},
{
type : float,
name : metallic
},
{
type : float,
name : roughness
}
],
requires : [
uv0
],
shadingModel : lit,
blending : opaque
}
fragment {
void material(inout MaterialInputs material) {
prepareMaterial(material);
material.baseColor = texture(materialParams_texture, getUV0());
material.metallic = materialParams.metallic;
material.roughness = materialParams.roughness;
}
}
</code></pre>
<h2 id="material-block"><a class="header" href="#material-block">Material block</a></h2>
<p>The material block is mandatory block that contains a list of property pairs to
describe all non-shader data.</p>
<h3 id="general-name"><a class="header" href="#general-name">General: name</a></h3>
<p>Type
: <code>string</code></p>
<p>Value
: Any string. Double quotes are required if the name contains spaces.</p>
<p>Description
: Sets the name of the material. The name is retained at runtime for debugging
purpose.</p>
<pre><code class="language-json">material {
name : stone
}
material {
name : &quot;Wet pavement&quot;
}
</code></pre>
<h3 id="general-featurelevel"><a class="header" href="#general-featurelevel">General: featureLevel</a></h3>
<p>Type
: <code>number</code></p>
<p>Value
: An integer value, either 1, 2 or 3. Defaults to 1.</p>
<div class="table-wrapper"><table><thead><tr><th style="text-align: right">Feature Level</th><th style="text-align: left">Guaranteed features</th></tr></thead><tbody>
<tr><td style="text-align: right">1</td><td style="text-align: left">9 textures per material</td></tr>
<tr><td style="text-align: right">2</td><td style="text-align: left">9 textures per material, cubemap arrays, ESSL 3.10</td></tr>
<tr><td style="text-align: right">3</td><td style="text-align: left">12 textures per material, cubemap arrays, ESSL 3.10</td></tr>
</tbody></table>
</div>
<p>[Table [featureLevels]: Feature levels]</p>
<p>Description
: Sets the feature level of the material. Each feature level defines a set of
features the material can use. If the material uses a feature not supported
by the selected level, <code>matc</code> will generate an error during compilation. A
given feature level is guaranteed to support all features of lower feature
levels.</p>
<pre><code class="language-json">material {
featureLevel : 2
}
</code></pre>
<p>Bugs
: <code>matc</code> doesn't verify that a material is not using features above its
selected feature level.</p>
<h3 id="general-shadingmodel"><a class="header" href="#general-shadingmodel">General: shadingModel</a></h3>
<p>Type
: <code>string</code></p>
<p>Value
: Any of <code>lit</code>, <code>subsurface</code>, <code>cloth</code>, <code>unlit</code>, <code>specularGlossiness</code>. Defaults
to <code>lit</code>.</p>
<p>Description
: Selects the material model as described in the Material models section.</p>
<pre><code class="language-json">material {
shadingModel : unlit
}
material {
shadingModel : &quot;subsurface&quot;
}
</code></pre>
<h3 id="general-parameters"><a class="header" href="#general-parameters">General: parameters</a></h3>
<p>Type
: array of parameter objects</p>
<p>Value
: Each entry is an object with the properties <code>name</code> and <code>type</code>, both of
<code>string</code> type. The name must be a valid GLSL identifier. Entries also have
an optional <code>precision</code>, which can be one of <code>default</code> (best precision for
the platform, typically <code>high</code> on desktop, <code>medium</code> on mobile), <code>low</code>,
<code>medium</code>, <code>high</code>. The type must be one of the types described in table
[materialParamsTypes].</p>
<div class="table-wrapper"><table><thead><tr><th style="text-align: right">Type</th><th style="text-align: left">Description</th></tr></thead><tbody>
<tr><td style="text-align: right">bool</td><td style="text-align: left">Single boolean</td></tr>
<tr><td style="text-align: right">bool2</td><td style="text-align: left">Vector of 2 booleans</td></tr>
<tr><td style="text-align: right">bool3</td><td style="text-align: left">Vector of 3 booleans</td></tr>
<tr><td style="text-align: right">bool4</td><td style="text-align: left">Vector of 4 booleans</td></tr>
<tr><td style="text-align: right">float</td><td style="text-align: left">Single float</td></tr>
<tr><td style="text-align: right">float2</td><td style="text-align: left">Vector of 2 floats</td></tr>
<tr><td style="text-align: right">float3</td><td style="text-align: left">Vector of 3 floats</td></tr>
<tr><td style="text-align: right">float4</td><td style="text-align: left">Vector of 4 floats</td></tr>
<tr><td style="text-align: right">int</td><td style="text-align: left">Single integer</td></tr>
<tr><td style="text-align: right">int2</td><td style="text-align: left">Vector of 2 integers</td></tr>
<tr><td style="text-align: right">int3</td><td style="text-align: left">Vector of 3 integers</td></tr>
<tr><td style="text-align: right">int4</td><td style="text-align: left">Vector of 4 integers</td></tr>
<tr><td style="text-align: right">uint</td><td style="text-align: left">Single unsigned integer</td></tr>
<tr><td style="text-align: right">uint2</td><td style="text-align: left">Vector of 2 unsigned integers</td></tr>
<tr><td style="text-align: right">uint3</td><td style="text-align: left">Vector of 3 unsigned integers</td></tr>
<tr><td style="text-align: right">uint4</td><td style="text-align: left">Vector of 4 unsigned integers</td></tr>
<tr><td style="text-align: right">float3x3</td><td style="text-align: left">Matrix of 3x3 floats</td></tr>
<tr><td style="text-align: right">float4x4</td><td style="text-align: left">Matrix of 4x4 floats</td></tr>
<tr><td style="text-align: right">sampler2d</td><td style="text-align: left">2D texture</td></tr>
<tr><td style="text-align: right">sampler2dArray</td><td style="text-align: left">Array of 2D textures</td></tr>
<tr><td style="text-align: right">samplerExternal</td><td style="text-align: left">External texture (platform-specific)</td></tr>
<tr><td style="text-align: right">samplerCubemap</td><td style="text-align: left">Cubemap texture</td></tr>
</tbody></table>
</div>
<p>[Table [materialParamsTypes]: Material parameter types]</p>
<p>Samplers
: Sampler types can also specify a <code>format</code> which can be either <code>int</code> or
<code>float</code> (defaults to <code>float</code>).</p>
<p>Arrays
: A parameter can define an array of values by appending <code>[size]</code> after the
type name, where <code>size</code> is a positive integer. For instance: <code>float[9]</code>
declares an array of nine <code>float</code> values. This syntax does not apply to
samplers as arrays are treated as separate types.</p>
<p>Description
: Lists the parameters required by your material. These parameters can be set
at runtime using Filament's material API. Accessing parameters from the
shaders varies depending on the type of parameter:</p>
<pre><code>- **Samplers types**: use the parameter name prefixed with
`materialParams_`. For instance, `materialParams_myTexture`.
- **Other types**: use the parameter name as the field of a structure
called `materialParams`. For instance, `materialParams.myColor`.
</code></pre>
<pre><code class="language-json">material {
parameters : [
{
type : float4,
name : albedo
},
{
type : sampler2d,
format : float,
precision : high,
name : roughness
},
{
type : float2,
name : metallicReflectance
}
],
requires : [
uv0
],
shadingModel : lit,
}
fragment {
void material(inout MaterialInputs material) {
prepareMaterial(material);
material.baseColor = materialParams.albedo;
material.roughness = texture(materialParams_roughness, getUV0());
material.metallic = materialParams.metallicReflectance.x;
material.reflectance = materialParams.metallicReflectance.y;
}
}
</code></pre>
<h3 id="general-constants"><a class="header" href="#general-constants">General: constants</a></h3>
<p>Type
: array of constant objects</p>
<p>Value
: Each entry is an object with the properties <code>name</code> and <code>type</code>, both of
<code>string</code> type. The name must be a valid GLSL identifier. Entries also have
an optional <code>default</code>, which can either be a <code>bool</code> or <code>number</code>, depending
on the <code>type</code> of the constant. The type must be one of the types described
in table [materialConstantsTypes].</p>
<div class="table-wrapper"><table><thead><tr><th style="text-align: right">Type</th><th style="text-align: left">Description</th><th style="text-align: left">Default</th></tr></thead><tbody>
<tr><td style="text-align: right">int</td><td style="text-align: left">A signed, 32 bit GLSL int</td><td style="text-align: left"></td></tr>
<tr><td style="text-align: right">float</td><td style="text-align: left">A single-precision GLSL float</td><td style="text-align: left">0.0</td></tr>
<tr><td style="text-align: right">bool</td><td style="text-align: left">A GLSL bool</td><td style="text-align: left">false</td></tr>
</tbody></table>
</div>
<p>[Table [materialConstantsTypes]: Material constants types]</p>
<p>Description
: Lists the constant parameters accepted by your material. These constants can
be set, or &quot;specialized&quot;, at runtime when loading a material package.
Multiple materials can be loaded from the same material package with
differing constant parameter specializations. Once a material is loaded from
a material package, its constant parameters cannot be changed. Compared to
regular parameters, constant parameters allow the compiler to generate more
efficient code. Access constant parameters from the shader by prefixing the
name with <code>materialConstant_</code>. For example, a constant parameter named
<code>myConstant</code> is accessed in the shader as <code>materialConstant_myConstant</code>. If
a constant parameter is not set at runtime, the default is used.</p>
<pre><code class="language-json">material {
constants : [
{
name : overrideAlpha,
type : bool
},
{
name : customAlpha,
type : float,
default : 0.5
}
],
shadingModel : lit,
blending : transparent,
}
fragment {
void material(inout MaterialInputs material) {
prepareMaterial(material);
if (materialConstants_overrideAlpha) {
material.baseColor.a = materialConstants_customAlpha;
material.baseColor.rgb *= material.baseColor.a;
}
}
}
</code></pre>
<h3 id="general-variantfilter"><a class="header" href="#general-variantfilter">General: variantFilter</a></h3>
<p>Type
: array of <code>string</code></p>
<p>Value
: Each entry must be any of <code>dynamicLighting</code>, <code>directionalLighting</code>,
<code>shadowReceiver</code>, <code>skinning</code>, <code>ssr</code>, or <code>stereo</code>.</p>
<p>Description
: Used to specify a list of shader variants that the application guarantees
will never be needed. These shader variants are skipped during the code
generation phase, thus reducing the overall size of the material. Note that
some variants may automatically be filtered out. For instance, all lighting
related variants (<code>directionalLighting</code>, etc.) are filtered out when
compiling an <code>unlit</code> material. Use the variant filter with caution,
filtering out a variant required at runtime may lead to crashes.</p>
<p>Description of the variants: - <code>directionalLighting</code>, used when a directional
light is present in the scene - <code>dynamicLighting</code>, used when a non-directional
light (point, spot, etc.) is present in the scene - <code>shadowReceiver</code>, used when
an object can receive shadows - <code>skinning</code>, used when an object is animated
using GPU skinning - <code>fog</code>, used when global fog is applied to the scene -
<code>vsm</code>, used when VSM shadows are enabled and the object is a shadow receiver -
<code>ssr</code>, used when screen-space reflections are enabled in the View - <code>stereo</code>,
used when stereoscopic rendering is enabled in the View</p>
<pre><code class="language-json">material {
name : &quot;Invisible shadow plane&quot;,
shadingModel : unlit,
shadowMultiplier : true,
blending : transparent,
variantFilter : [ skinning ]
}
</code></pre>
<h3 id="general-flipuv"><a class="header" href="#general-flipuv">General: flipUV</a></h3>
<p>Type
: <code>boolean</code></p>
<p>Value
: <code>true</code> or <code>false</code>. Defaults to <code>true</code>.</p>
<p>Description
: When set to <code>true</code> (default value), the Y coordinate of UV attributes will
be flipped when read by this material's vertex shader. Flipping is
equivalent to <code>y = 1.0 - y</code>. When set to <code>false</code>, flipping is disabled and
the UV attributes are read as is.</p>
<pre><code class="language-json">material {
flipUV : false
}
</code></pre>
<h3 id="general-quality"><a class="header" href="#general-quality">General: quality</a></h3>
<p>Type
: <code>string</code></p>
<p>Value
: Any of <code>low</code>, <code>normal</code>, <code>high</code>, <code>default</code>. Defaults to <code>default</code>.</p>
<p>Description
: Set some global quality parameters of the material. <code>low</code> enables
optimizations that can slightly affect correctness and is the default on
mobile platforms. <code>normal</code> does not affect correctness and is otherwise
similar to <code>low</code>. <code>high</code> enables quality settings that can adversely affect
performance and is the default on desktop platforms.</p>
<pre><code class="language-json">material {
quality : default
}
</code></pre>
<h3 id="general-instanced"><a class="header" href="#general-instanced">General: instanced</a></h3>
<p>Type
: <code>boolean</code></p>
<p>Value
: <code>true</code> or <code>false</code>. Defaults to <code>false</code>.</p>
<p>Description
: Allows a material to access the instance index (i.e.:
<strong><code>gl_InstanceIndex</code></strong>) of instanced primitives using <code>getInstanceIndex()</code>
in the material's shader code. Never use <strong><code>gl_InstanceIndex</code></strong> directly.
This is typically used with <code>RenderableManager::Builder::instances()</code>.
<code>getInstanceIndex()</code> is available in both the vertex and fragment shader.</p>
<pre><code class="language-json">material {
instanced : true
}
</code></pre>
<h3 id="general-vertexdomaindevicejittered"><a class="header" href="#general-vertexdomaindevicejittered">General: vertexDomainDeviceJittered</a></h3>
<p>Type
: <code>boolean</code></p>
<p>Value
: <code>true</code> or <code>false</code>. Defaults to <code>false</code>.</p>
<p>Description
: Only meaningful for <code>vertexDomain:Device</code> materials, this parameter
specifies whether the filament clip-space transforms need to be applied or
not, which affects TAA and guard bands. Generally it needs to be applied
because by definition <code>vertexDomain:Device</code> materials vertices are not
transformed and used <em>as is</em>. However, if the vertex shader uses for
instance <code>getViewFromClipMatrix()</code> (or other matrices based on the
projection), the clip-space transform is already applied. Setting this
parameter incorrectly can prevent TAA or the guard bands to work correctly.</p>
<pre><code class="language-json">material {
vertexDomainDeviceJittered : true
}
</code></pre>
<h3 id="vertex-and-attributes-requires"><a class="header" href="#vertex-and-attributes-requires">Vertex and attributes: requires</a></h3>
<p>Type
: array of <code>string</code></p>
<p>Value
: Each entry must be any of <code>uv0</code>, <code>uv1</code>, <code>color</code>, <code>position</code>, <code>tangents</code>,
<code>custom0</code> through <code>custom7</code>.</p>
<p>Description
: Lists the vertex attributes required by the material. The <code>position</code>
attribute is always required and does not need to be specified. The
<code>tangents</code> attribute is automatically required when selecting any shading
model that is not <code>unlit</code>. See the shader sections of this document for more
information on how to access these attributes from the shaders.</p>
<pre><code class="language-json">material {
parameters : [
{
type : sampler2d,
name : texture
},
],
requires : [
uv0,
custom0
],
shadingModel : lit,
}
fragment {
void material(inout MaterialInputs material) {
prepareMaterial(material);
material.baseColor = texture(materialParams_texture, getUV0());
material.baseColor.rgb *= getCustom0().rgb;
}
}
</code></pre>
<h3 id="vertex-and-attributes-variables"><a class="header" href="#vertex-and-attributes-variables">Vertex and attributes: variables</a></h3>
<p>Type
: array of <code>string</code></p>
<p>Value
: Up to 4 strings, each must be a valid GLSL identifier.</p>
<p>Description
: Defines custom interpolants (or variables) that are output by the material's
vertex shader. Each entry of the array defines the name of an interpolant.
The full name in the fragment shader is the name of the interpolant with the
<code>variable_</code> prefix. For instance, if you declare a variable called
<code>eyeDirection</code> you can access it in the fragment shader using
<code>variable_eyeDirection</code>. In the vertex shader, the interpolant name is
simply a member of the <code>MaterialVertexInputs</code> structure
(<code>material.eyeDirection</code> in your example). Each interpolant is of type
<code>float4</code> (<code>vec4</code>) in the shaders.</p>
<pre><code class="language-json">material {
name : Skybox,
parameters : [
{
type : samplerCubemap,
name : skybox
}
],
variables : [
eyeDirection
],
vertexDomain : device,
depthWrite : false,
shadingModel : unlit
}
fragment {
void material(inout MaterialInputs material) {
prepareMaterial(material);
float3 sky = texture(materialParams_skybox, variable_eyeDirection.xyz).rgb;
material.baseColor = vec4(sky, 1.0);
}
}
vertex {
void materialVertex(inout MaterialVertexInputs material) {
float3 p = getPosition().xyz;
float3 u = mulMat4x4Float3(getViewFromClipMatrix(), p).xyz;
material.eyeDirection.xyz = mulMat3x3Float3(getWorldFromViewMatrix(), u);
}
}
</code></pre>
<h3 id="vertex-and-attributes-vertexdomain"><a class="header" href="#vertex-and-attributes-vertexdomain">Vertex and attributes: vertexDomain</a></h3>
<p>Type
: <code>string</code></p>
<p>Value
: Any of <code>object</code>, <code>world</code>, <code>view</code>, <code>device</code>. Defaults to <code>object</code>.</p>
<p>Description
: Defines the domain (or coordinate space) of the rendered mesh. The domain
influences how the vertices are transformed in the vertex shader. The
possible domains are:</p>
<pre><code>- **Object**: the vertices are defined in the object (or model) coordinate
space. The vertices are transformed using the rendered object's
transform matrix
- **World**: the vertices are defined in world coordinate space. The
vertices are not transformed using the rendered object's transform.
- **View**: the vertices are defined in view (or eye or camera) coordinate
space. The vertices are not transformed using the rendered object's
transform.
- **Device**: the vertices are defined in normalized device (or clip)
coordinate space. The vertices are not transformed using the rendered
object's transform.
</code></pre>
<pre><code class="language-json">material {
vertexDomain : device
}
</code></pre>
<h3 id="vertex-and-attributes-interpolation"><a class="header" href="#vertex-and-attributes-interpolation">Vertex and attributes: interpolation</a></h3>
<p>Type
: <code>string</code></p>
<p>Value
: Any of <code>smooth</code>, <code>flat</code>. Defaults to <code>smooth</code>.</p>
<p>Description
: Defines how interpolants (or variables) are interpolated between vertices.
When this property is set to <code>smooth</code>, a perspective correct interpolation
is performed on each interpolant. When set to <code>flat</code>, no interpolation is
performed and all the fragments within a given triangle will be shaded the
same.</p>
<pre><code class="language-json">material {
interpolation : flat
}
</code></pre>
<h3 id="blending-and-transparency-blending"><a class="header" href="#blending-and-transparency-blending">Blending and transparency: blending</a></h3>
<p>Type
: <code>string</code></p>
<p>Value
: Any of <code>opaque</code>, <code>transparent</code>, <code>fade</code>, <code>add</code>, <code>masked</code>, <code>multiply</code>,
<code>screen</code>. Defaults to <code>opaque</code>.</p>
<p>Description
: Defines how/if the rendered object is blended with the content of the render
target. The possible blending modes are:</p>
<pre><code>- **Opaque**: blending is disabled, the alpha channel of the material's
output is ignored.
- **Transparent**: blending is enabled. The material's output is alpha
composited with the render target, using Porter-Duff's `source over`
rule. This blending mode assumes pre-multiplied alpha.
- **Fade**: acts as `transparent` but transparency is also applied to
specular lighting. In `transparent` mode, the material's alpha values
only applies to diffuse lighting. This blending mode is useful to fade
lit objects in and out.
- **Add**: blending is enabled. The material's output is added to the
content of the render target.
- **Multiply**: blending is enabled. The material's output is multiplied
with the content of the render target, darkening the content.
- **Screen**: blending is enabled. Effectively the opposite of the
`multiply`, the content of the render target is brightened.
- **Masked**: blending is disabled. This blending mode enables alpha
masking. The alpha channel of the material's output defines whether a
fragment is discarded or not. Additionally, ALPHA_TO_COVERAGE is enabled
for non-translucent views. See the maskThreshold section for more
information.
</code></pre>
<p>!!! Note When <code>blending</code> is set to <code>masked</code>, alpha to coverage is automatically
enabled for the material. If this behavior is undesirable, refer to the
Rasterization: alphaToCoverage section to turn alpha to coverage off using the
<code>alphaToCoverage</code> property.</p>
<pre><code class="language-json">material {
blending : transparent
}
</code></pre>
<h3 id="blending-and-transparency-postlightingblending"><a class="header" href="#blending-and-transparency-postlightingblending">Blending and transparency: postLightingBlending</a></h3>
<p>Type
: <code>string</code></p>
<p>Value
: Any of <code>opaque</code>, <code>transparent</code>, <code>add</code>. Defaults to <code>transparent</code>.</p>
<p>Description
: Defines how the <code>postLightingColor</code> material property is blended with the
result of the lighting computations. The possible blending modes are:</p>
<pre><code>- **Opaque**: blending is disabled, the material will output
`postLightingColor` directly.
- **Transparent**: blending is enabled. The material's computed color is
alpha composited with the `postLightingColor`, using Porter-Duff's
`source over` rule. This blending mode assumes pre-multiplied alpha.
- **Add**: blending is enabled. The material's computed color is added to
`postLightingColor`.
- **Multiply**: blending is enabled. The material's computed color is
multiplied with `postLightingColor`.
- **Screen**: blending is enabled. The material's computed color is
inverted and multiplied with `postLightingColor`, and the result is
added to the material's computed color.
</code></pre>
<pre><code class="language-json">material {
postLightingBlending : add
}
</code></pre>
<h3 id="blending-and-transparency-transparency"><a class="header" href="#blending-and-transparency-transparency">Blending and transparency: transparency</a></h3>
<p>Type
: <code>string</code></p>
<p>Value
: Any of <code>default</code>, <code>twoPassesOneSide</code> or <code>twoPassesTwoSides</code>. Defaults to
<code>default</code>.</p>
<p>Description
: Controls how transparent objects are rendered. It is only valid when the
<code>blending</code> mode is not <code>opaque</code> and <code>refractionMode</code> is <code>none</code>. None of
these methods can accurately render concave geometry, but in practice they
are often good enough.</p>
<p>The three possible transparency modes are: - <code>default</code>: the transparent object
is rendered normally (as seen in figure [transparencyDefault]), honoring the
<code>culling</code> mode, etc. - <code>twoPassesOneSide</code>: the transparent object is first
rendered in the depth buffer, then again in the color buffer, honoring the
<code>culling</code> mode. This effectively renders only half of the transparent object as
shown in figure [transparencyTwoPassesOneSide]. - <code>twoPassesTwoSides</code>: the
transparent object is rendered twice in the color buffer: first with its back
faces, then with its front faces. This mode lets you render both set of faces
while reducing or eliminating sorting issues, as shown in figure
[transparencyTwoPassesTwoSides]. <code>twoPassesTwoSides</code> can be combined with
<code>doubleSided</code> for better effect.</p>
<pre><code class="language-json">material {
transparency : twoPassesOneSide
}
</code></pre>
<p><img src="images/screenshot_transparency_default.png" alt="Figure [transparencyDefault]: This double sided model shows the type of sorting issues transparent objects can be subject to in default mode" /></p>
<p><img src="images/screenshot_twopasses_oneside.png" alt="Figure [transparencyTwoPassesOneSide]: In twoPassesOneSide mode, only one set of faces is visible and correctly sorted" /></p>
<p><img src="images/screenshot_twopasses_twosides.png" alt="Figure [transparencyTwoPassesTwoSides]: In twoPassesTwoSides mode, both set of faces are visible and sorting issues are minimized or eliminated" /></p>
<h3 id="blending-and-transparency-maskthreshold"><a class="header" href="#blending-and-transparency-maskthreshold">Blending and transparency: maskThreshold</a></h3>
<p>Type
: <code>number</code></p>
<p>Value
: A value between <code>0.0</code> and <code>1.0</code>. Defaults to <code>0.4</code>.</p>
<p>Description
: Sets the minimum alpha value a fragment must have to not be discarded when
the <code>blending</code> mode is set to <code>masked</code>. If the fragment is not discarded,
its source alpha is set to 1. When the blending mode is not <code>masked</code>, this
value is ignored. This value can be used to controlled the appearance of
alpha-masked objects.</p>
<pre><code class="language-json">material {
blending : masked,
maskThreshold : 0.5
}
</code></pre>
<h3 id="blending-and-transparency-refractionmode"><a class="header" href="#blending-and-transparency-refractionmode">Blending and transparency: refractionMode</a></h3>
<p>Type
: <code>string</code></p>
<p>Value
: Any of <code>none</code>, <code>cubemap</code>, <code>screenspace</code>. Defaults to <code>none</code>.</p>
<p>Description
: Activates refraction when set to anything but <code>none</code>. A value of <code>cubemap</code>
will only use the IBL cubemap as source of refraction, while this is
significantly more efficient, no scene objects will be refracted, only the
distant environment encoded in the cubemap. This mode is adequate for an
object viewer for instance. A value of <code>screenspace</code> will employ the more
advanced screen-space refraction algorithm which allows opaque objects in
the scene to be refracted. In <code>cubemap</code> mode, refracted rays are assumed to
emerge from the center of the object and the <code>thickness</code> parameter is only
used for computing the absorption, but has no impact on the refraction
itself. In <code>screenspace</code> mode, refracted rays are assumed to travel parallel
to the view direction when they exit the refractive medium.</p>
<pre><code class="language-json">material {
refractionMode : cubemap,
}
</code></pre>
<h3 id="blending-and-transparency-refractiontype"><a class="header" href="#blending-and-transparency-refractiontype">Blending and transparency: refractionType</a></h3>
<p>Type
: <code>string</code></p>
<p>Value
: Any of <code>solid</code>, <code>thin</code>. Defaults to <code>solid</code>.</p>
<p>Description
: This is only meaningful when <code>refractionMode</code> is set to anything but <code>none</code>.
<code>refractionType</code> defines the refraction model used. <code>solid</code> is used for
thick objects such as a crystal ball, an ice cube or as sculpture. <code>thin</code> is
used for thin objects such as a window, an ornament ball or a soap bubble.
In <code>solid</code> mode all refracive objects are assumed to be a sphere tangent to
the entry point and of radius <code>thickness</code>. In <code>thin</code> mode, all refractive
objects are assumed to be flat and thin and of thickness <code>thickness</code>.</p>
<pre><code class="language-json">material {
refractionMode : cubemap,
refractionType : thin,
}
</code></pre>
<h3 id="rasterization-culling"><a class="header" href="#rasterization-culling">Rasterization: culling</a></h3>
<p>Type
: <code>string</code></p>
<p>Value
: Any of <code>none</code>, <code>front</code>, <code>back</code>, <code>frontAndBack</code>. Defaults to <code>back</code>.</p>
<p>Description
: Defines which triangles should be culled: none, front-facing triangles,
back-facing triangles or all.</p>
<pre><code class="language-json">material {
culling : none
}
</code></pre>
<h3 id="rasterization-colorwrite"><a class="header" href="#rasterization-colorwrite">Rasterization: colorWrite</a></h3>
<p>Type
: <code>boolean</code></p>
<p>Value
: <code>true</code> or <code>false</code>. Defaults to <code>true</code>.</p>
<p>Description
: Enables or disables writes to the color buffer.</p>
<pre><code class="language-json">material {
colorWrite : false
}
</code></pre>
<h3 id="rasterization-depthwrite"><a class="header" href="#rasterization-depthwrite">Rasterization: depthWrite</a></h3>
<p>Type
: <code>boolean</code></p>
<p>Value
: <code>true</code> or <code>false</code>. Defaults to <code>true</code> for opaque materials, <code>false</code> for
transparent materials.</p>
<p>Description
: Enables or disables writes to the depth buffer.</p>
<pre><code class="language-json">material {
depthWrite : false
}
</code></pre>
<h3 id="rasterization-depthculling"><a class="header" href="#rasterization-depthculling">Rasterization: depthCulling</a></h3>
<p>Type
: <code>boolean</code></p>
<p>Value
: <code>true</code> or <code>false</code>. Defaults to <code>true</code>.</p>
<p>Description
: Enables or disables depth testing. When depth testing is disabled, an object
rendered with this material will always appear on top of other opaque
objects.</p>
<pre><code class="language-json">material {
depthCulling : false
}
</code></pre>
<h3 id="rasterization-doublesided"><a class="header" href="#rasterization-doublesided">Rasterization: doubleSided</a></h3>
<p>Type
: <code>boolean</code></p>
<p>Value
: <code>true</code> or <code>false</code>. Defaults to <code>false</code>.</p>
<p>Description
: Enables two-sided rendering and its capability to be toggled at run time.
When set to <code>true</code>, <code>culling</code> is automatically set to <code>none</code>; if the
triangle is back-facing, the triangle's normal is flipped to become
front-facing. When explicitly set to <code>false</code>, this allows the
double-sidedness to be toggled at run time.</p>
<pre><code class="language-json">material {
name : &quot;Double sided material&quot;,
shadingModel : lit,
doubleSided : true
}
fragment {
void material(inout MaterialInputs material) {
prepareMaterial(material);
material.baseColor = materialParams.albedo;
}
}
</code></pre>
<h3 id="rasterization-alphatocoverage"><a class="header" href="#rasterization-alphatocoverage">Rasterization: alphaToCoverage</a></h3>
<p>Type
: <code>boolean</code></p>
<p>Value
: <code>true</code> or <code>false</code>. Defaults to <code>false</code>.</p>
<p>Description
: Enables or disables alpha to coverage. When alpha to coverage is enabled,
the coverage of fragment is derived from its alpha. This property is only
meaningful when MSAA is enabled. Note: setting <code>blending</code> to <code>masked</code>
automatically enables alpha to coverage. If this is not desired, you can
override this behavior by setting alpha to coverage to false as in the
example below.</p>
<pre><code class="language-json">material {
name : &quot;Alpha to coverage&quot;,
shadingModel : lit,
blending : masked,
alphaToCoverage : false
}
fragment {
void material(inout MaterialInputs material) {
prepareMaterial(material);
material.baseColor = materialParams.albedo;
}
}
</code></pre>
<h3 id="lighting-reflections"><a class="header" href="#lighting-reflections">Lighting: reflections</a></h3>
<p>Type
: <code>string</code></p>
<p>Value
: <code>default</code> or <code>screenspace</code>. Defaults to <code>default</code>.</p>
<p>Description
: Controls the source of specular reflections for this material. When this
property is set to <code>default</code>, reflections only come image-based lights. When
this property is set to <code>screenspace</code>, reflections come from the screen
space's color buffer in addition to image-based lights.</p>
<pre><code class="language-json">material {
name : &quot;Glossy metal&quot;,
reflections : screenspace
}
</code></pre>
<h3 id="lighting-shadowmultiplier"><a class="header" href="#lighting-shadowmultiplier">Lighting: shadowMultiplier</a></h3>
<p>Type
: <code>boolean</code></p>
<p>Value
: <code>true</code> or <code>false</code>. Defaults to <code>false</code>.</p>
<p>Description
: Only available in the <code>unlit</code> shading model. If this property is enabled,
the final color computed by the material is multiplied by the shadowing
factor (or visibility). This allows to create transparent shadow-receiving
objects (for instance an invisible ground plane in AR). This is only
supported with shadows from directional lights.</p>
<pre><code class="language-json">material {
name : &quot;Invisible shadow plane&quot;,
shadingModel : unlit,
shadowMultiplier : true,
blending : transparent
}
fragment {
void material(inout MaterialInputs material) {
prepareMaterial(material);
// baseColor defines the color and opacity of the final shadow
material.baseColor = vec4(0.0, 0.0, 0.0, 0.7);
}
}
</code></pre>
<h3 id="lighting-transparentshadow"><a class="header" href="#lighting-transparentshadow">Lighting: transparentShadow</a></h3>
<p>Type
: <code>boolean</code></p>
<p>Value
: <code>true</code> or <code>false</code>. Defaults to <code>false</code>.</p>
<p>Description
: Enables transparent shadows on this material. When this feature is enabled,
Filament emulates transparent shadows using a dithering pattern: they work
best with variance shadow maps (VSM) and blurring enabled. The opacity of
the shadow derives directly from the alpha channel of the material's
<code>baseColor</code> property. Transparent shadows can be enabled on opaque objects,
making them compatible with refractive/transmissive objects that are
otherwise considered opaque.</p>
<pre><code class="language-json">material {
name : &quot;Clear plastic with stickers&quot;,
transparentShadow : true,
blending : transparent,
// ...
}
fragment {
void material(inout MaterialInputs material) {
prepareMaterial(material);
material.baseColor = texture(materialParams_baseColor, getUV0());
}
}
</code></pre>
<p><img src="images/screenshot_transparent_shadows.jpg" alt="Figure [transparentShadow]: Objects rendered with transparent shadows and blurry VSM with a radius of 4. Model Bottle of Water by T-Art." /></p>
<h3 id="lighting-clearcoatiorchange"><a class="header" href="#lighting-clearcoatiorchange">Lighting: clearCoatIorChange</a></h3>
<p>Type
: <code>boolean</code></p>
<p>Value
: <code>true</code> or <code>false</code>. Defaults to <code>true</code>.</p>
<p>Description
: When adding a clear coat layer, the change in index of refraction (IoR) is
taken into account to modify the specular color of the base layer. This
appears to darken <code>baseColor</code>. When this effect is disabled, <code>baseColor</code> is
left unmodified. See figure [clearCoatIorChange] for an example of how this
property can affect a red metallic base layer.</p>
<pre><code class="language-json">material {
clearCoatIorChange : false
}
</code></pre>
<p><img src="images/screenshot_clear_coat_ior_change.jpg" alt="Figure [clearCoatIorChange]: The same rough metallic ball with a clear coat layer rendered with clearCoatIorChange enabled (left) and disabled (right)." /></p>
<h3 id="lighting-multibounceambientocclusion"><a class="header" href="#lighting-multibounceambientocclusion">Lighting: multiBounceAmbientOcclusion</a></h3>
<p>Type
: <code>boolean</code></p>
<p>Value
: <code>true</code> or <code>false</code>. Defaults to <code>false</code> on mobile, <code>true</code> on desktop.</p>
<p>Description
: Multi-bounce ambient occlusion takes into account interreflections when
applying ambient occlusion to image-based lighting. Turning this feature on
avoids over-darkening occluded areas. It also takes the surface color into
account to generate colored ambient occlusion. Figure [multiBounceAO]
compares the ambient occlusion term of a surface with and without
multi-bounce ambient occlusion. Notice how multi-bounce ambient occlusion
introduces color in the occluded areas. Figure [multiBounceAOAnimated]
toggles between multi-bounce ambient occlusion on and off on a lit brick
material to highlight the effects of this property.</p>
<pre><code class="language-json">material {
multiBounceAmbientOcclusion : true
}
</code></pre>
<p><img src="images/screenshot_multi_bounce_ao.jpg" alt="Figure [multiBounceAO]: Brick texture amient occlusion map rendered with multi-bounce ambient occclusion enabled (left) and disabled (right)." /></p>
<p><img src="images/screenshot_multi_bounce_ao.gif" alt="Figure [multiBounceAOAnimated]: Brick texture rendered with multi-bounce ambient occclusion enabled and disabled." /></p>
<h3 id="lighting-specularambientocclusion"><a class="header" href="#lighting-specularambientocclusion">Lighting: specularAmbientOcclusion</a></h3>
<p>Type
: <code>string</code></p>
<p>Value
: <code>none</code>, <code>simple</code> or <code>bentNormals</code>. Defaults to <code>none</code> on mobile, <code>simple</code> on
desktop. For compatibility reasons, <code>true</code> and <code>false</code> are also accepted and
map respectively to <code>simple</code> and <code>none</code>.</p>
<p>Description
: Static ambient occlusion maps and dynamic ambient occlusion (SSAO, etc.)
apply to diffuse indirect lighting. When setting this property to other than
<code>none</code>, a new ambient occlusion term is derived from the surface roughness
and applied to specular indirect lighting. This effect helps remove unwanted
specular reflections as shown in figure [specularAO]. When this value is set
to <code>simple</code>, Filament uses a cheap but approximate method of computing the
specular ambient occlusion term. If this value is set to <code>bentNormals</code>,
Filament will use a much more accurate but much more expensive method.</p>
<pre><code class="language-json">material {
specularAmbientOcclusion : simple
}
</code></pre>
<p><img src="images/screenshot_specular_ao.gif" alt="Figure [specularAO]: Comparison of specular ambient occlusion on and off. The effect is particularly visible under the hose." /></p>
<h3 id="anti-aliasing-specularantialiasing"><a class="header" href="#anti-aliasing-specularantialiasing">Anti-aliasing: specularAntiAliasing</a></h3>
<p>Type
: <code>boolean</code></p>
<p>Value
: <code>true</code> or <code>false</code>. Defaults to <code>false</code>.</p>
<p>Description
: Reduces specular aliasing and preserves the shape of specular highlights as
an object moves away from the camera. This anti-aliasing solution is
particularly effective on glossy materials (low roughness) but increases the
cost of the material. The strength of the anti-aliasing effect can be
controlled using two other properties: <code>specularAntiAliasingVariance</code> and
<code>specularAntiAliasingThreshold</code>.</p>
<pre><code class="language-json">material {
specularAntiAliasing : true
}
</code></pre>
<h3 id="anti-aliasing-specularantialiasingvariance"><a class="header" href="#anti-aliasing-specularantialiasingvariance">Anti-aliasing: specularAntiAliasingVariance</a></h3>
<p>Type
: <code>float</code></p>
<p>Value
: A value between 0 and 1, set to 0.15 by default.</p>
<p>Description
: Sets the screen space variance of the filter kernel used when applying
specular anti-aliasing. Higher values will increase the effect of the filter
but may increase roughness in unwanted areas.</p>
<pre><code class="language-json">material {
specularAntiAliasingVariance : 0.2
}
</code></pre>
<h3 id="anti-aliasing-specularantialiasingthreshold"><a class="header" href="#anti-aliasing-specularantialiasingthreshold">Anti-aliasing: specularAntiAliasingThreshold</a></h3>
<p>Type
: <code>float</code></p>
<p>Value
: A value between 0 and 1, set to 0.2 by default.</p>
<p>Description
: Sets the clamping threshold used to suppress estimation errors when applying
specular anti-aliasing. When set to 0, specular anti-aliasing is disabled.</p>
<pre><code class="language-json">material {
specularAntiAliasingThreshold : 0.1
}
</code></pre>
<h3 id="shading-customsurfaceshading"><a class="header" href="#shading-customsurfaceshading">Shading: customSurfaceShading</a></h3>
<p>Type
: <code>bool</code></p>
<p>Value
: <code>true</code> or <code>false</code>. Defaults to <code>false</code>.</p>
<p>Description
: Enables custom surface shading when set to true. When surface shading is
enabled, the fragment shader must provide an extra function that will be
invoked for every light in the scene that may influence the current
fragment. Please refer to the Custom surface shading section below for more
information.</p>
<pre><code class="language-json">material {
customSurfaceShading : true
}
</code></pre>
<h2 id="vertex-block"><a class="header" href="#vertex-block">Vertex block</a></h2>
<p>The vertex block is optional and can be used to control the vertex shading stage
of the material. The vertex block must contain valid
<a href="https://www.khronos.org/registry/OpenGL/specs/es/3.0/GLSL_ES_Specification_3.00.pdf">ESSL 3.0</a>
code (the version of GLSL supported in OpenGL ES 3.0). You are free to create
multiple functions inside the vertex block but you <strong>must</strong> declare the
<code>materialVertex</code> function:</p>
<pre><code class="language-glsl">vertex {
void materialVertex(inout MaterialVertexInputs material) {
// vertex shading code
}
}
</code></pre>
<p>This function will be invoked automatically at runtime by the shading system and
gives you the ability to read and modify material properties using the
<code>MaterialVertexInputs</code> structure. This full definition of the structure can be
found in the Material vertex inputs section.</p>
<p>You can use this structure to compute your custom variables/interpolants or to
modify the value of the attributes. For instance, the following vertex blocks
modifies both the color and the UV coordinates of the vertex over time:</p>
<pre><code class="language-glsl">material {
requires : [uv0, color]
}
vertex {
void materialVertex(inout MaterialVertexInputs material) {
material.color *= sin(getUserTime().x);
material.uv0 *= sin(getUserTime().x);
}
}
</code></pre>
<p>In addition to the <code>MaterialVertexInputs</code> structure, your vertex shading code
can use all the public APIs listed in the Shader public APIs section.</p>
<h3 id="material-vertex-inputs"><a class="header" href="#material-vertex-inputs">Material vertex inputs</a></h3>
<pre><code class="language-glsl">struct MaterialVertexInputs {
float4 color; // if the color attribute is required
float2 uv0; // if the uv0 attribute is required
float2 uv1; // if the uv1 attribute is required
float3 worldNormal; // only if the shading model is not unlit
float4 worldPosition; // always available (see note below about world-space)
mat4 clipSpaceTransform; // default: identity, transforms the clip-space position, only available for `vertexDomain:device`
// variable* names are replaced with actual names
float4 variable0; // if 1 or more variables is defined
float4 variable1; // if 2 or more variables is defined
float4 variable2; // if 3 or more variables is defined
float4 variable3; // if 4 or more variables is defined
};
</code></pre>
<p>!!! TIP: worldPosition To achieve good precision, the <code>worldPosition</code> coordinate
in the vertex shader is shifted by the camera position. To get the true
world-space position, users can use <code>getUserWorldPosition()</code>, however be aware
that the true world-position might not be able to fit in a <code>float</code> or might be
represented with severely reduced precision.</p>
<p>!!! TIP: UV attributes By default the vertex shader of a material will flip the
Y coordinate of the UV attributes of the current mesh: <code>material.uv0 = vec2(mesh_uv0.x, 1.0 - mesh_uv0.y)</code>. You can control this behavior using the
<code>flipUV</code> property and setting it to <code>false</code>.</p>
<h3 id="custom-vertex-attributes"><a class="header" href="#custom-vertex-attributes">Custom vertex attributes</a></h3>
<p>You can use up to 8 custom vertex attributes, all of type <code>float4</code>. These
attributes can be accessed using the vertex block shader functions
<code>getCustom0()</code> to <code>getCustom7()</code>. However, before using custom attributes, you
<em>must</em> declare those attributes as required in the <code>requires</code> property of the
material:</p>
<pre><code class="language-json">material {
requires : [
custom0,
custom1,
custom2
]
}
</code></pre>
<h2 id="fragment-block"><a class="header" href="#fragment-block">Fragment block</a></h2>
<p>The fragment block must be used to control the fragment shading stage of the
material. The fragment block must contain valid
<a href="https://www.khronos.org/registry/OpenGL/specs/es/3.0/GLSL_ES_Specification_3.00.pdf">ESSL 3.0</a>
code (the version of GLSL supported in OpenGL ES 3.0). You are free to create
multiple functions inside the fragment block but you <strong>must</strong> declare the
<code>material</code> function:</p>
<pre><code class="language-glsl">fragment {
void material(inout MaterialInputs material) {
prepareMaterial(material);
// fragment shading code
}
}
</code></pre>
<p>This function will be invoked automatically at runtime by the shading system and
gives you the ability to read and modify material properties using the
<code>MaterialInputs</code> structure. This full definition of the structure can be found
in the Material fragment inputs section. The full definition of the various
members of the structure can be found in the Material models section of this
document.</p>
<p>The goal of the <code>material()</code> function is to compute the material properties
specific to the selected shading model. For instance, here is a fragment block
that creates a glossy red metal using the standard lit shading model:</p>
<pre><code class="language-glsl">fragment {
void material(inout MaterialInputs material) {
prepareMaterial(material);
material.baseColor.rgb = vec3(1.0, 0.0, 0.0);
material.metallic = 1.0;
material.roughness = 0.0;
}
}
</code></pre>
<h3 id="preparematerial-function"><a class="header" href="#preparematerial-function">prepareMaterial function</a></h3>
<p>Note that you <strong>must</strong> call <code>prepareMaterial(material)</code> before exiting the
<code>material()</code> function. This <code>prepareMaterial</code> function sets up the internal
state of the material model. Some of the APIs described in the Fragment APIs
section - like <code>shading_normal</code> for instance - can only be accessed <em>after</em>
invoking <code>prepareMaterial()</code>.</p>
<p>It is also important to remember that the <code>normal</code> property - as described in
the Material fragment inputs section - only has an effect when modified <em>before</em>
calling <code>prepareMaterial()</code>. Here is an example of a fragment shader that
properly modifies the <code>normal</code> property to implement a glossy red plastic with
bump mapping:</p>
<pre><code class="language-glsl">fragment {
void material(inout MaterialInputs material) {
// fetch the normal in tangent space
vec3 normal = texture(materialParams_normalMap, getUV0()).xyz;
material.normal = normal * 2.0 - 1.0;
// prepare the material
prepareMaterial(material);
// from now on, shading_normal, etc. can be accessed
material.baseColor.rgb = vec3(1.0, 0.0, 0.0);
material.metallic = 0.0;
material.roughness = 1.0;
}
}
</code></pre>
<h3 id="material-fragment-inputs"><a class="header" href="#material-fragment-inputs">Material fragment inputs</a></h3>
<pre><code class="language-glsl">struct MaterialInputs {
float4 baseColor; // default: float4(1.0)
float4 emissive; // default: float4(0.0, 0.0, 0.0, 1.0)
float4 postLightingColor; // default: float4(0.0)
// no other field is available with the unlit shading model
float roughness; // default: 1.0
float metallic; // default: 0.0, not available with cloth or specularGlossiness
float reflectance; // default: 0.5, not available with cloth or specularGlossiness
float ambientOcclusion; // default: 0.0
// not available when the shading model is subsurface or cloth
float3 sheenColor; // default: float3(0.0)
float sheenRoughness; // default: 0.0
float clearCoat; // default: 1.0
float clearCoatRoughness; // default: 0.0
float3 clearCoatNormal; // default: float3(0.0, 0.0, 1.0)
float anisotropy; // default: 0.0
float3 anisotropyDirection; // default: float3(1.0, 0.0, 0.0)
// only available when the shading model is subsurface or refraction is enabled
float thickness; // default: 0.5
// only available when the shading model is subsurface
float subsurfacePower; // default: 12.234
float3 subsurfaceColor; // default: float3(1.0)
// only available when the shading model is cloth
float3 sheenColor; // default: sqrt(baseColor)
float3 subsurfaceColor; // default: float3(0.0)
// only available when the shading model is specularGlossiness
float3 specularColor; // default: float3(0.0)
float glossiness; // default: 0.0
// not available when the shading model is unlit
// must be set before calling prepareMaterial()
float3 normal; // default: float3(0.0, 0.0, 1.0)
// only available when refraction is enabled
float transmission; // default: 1.0
float3 absorption; // default float3(0.0, 0.0, 0.0)
float ior; // default: 1.5
float microThickness; // default: 0.0, not available with refractionType &quot;solid&quot;
}
</code></pre>
<h3 id="custom-surface-shading"><a class="header" href="#custom-surface-shading">Custom surface shading</a></h3>
<p>When <code>customSurfaceShading</code> is set to <code>true</code> in the material block, the fragment
block <strong>must</strong> declare and implement the <code>surfaceShading</code> function:</p>
<pre><code class="language-glsl">fragment {
void material(inout MaterialInputs material) {
prepareMaterial(material);
// prepare material inputs
}
vec3 surfaceShading(
const MaterialInputs materialInputs,
const ShadingData shadingData,
const LightData lightData
) {
return vec3(1.0); // output of custom lighting
}
}
</code></pre>
<p>This function will be invoked for every light (directional, spot or point) in
the scene that may influence the current fragment. The <code>surfaceShading</code> is
invoked with 3 sets of data:</p>
<ul>
<li><code>MaterialInputs</code>, as described in the Material fragment inputs section and
prepared in the <code>material</code> function explained above</li>
<li><code>ShadingData</code>, a structure containing values derived from <code>MaterialInputs</code>
(see below)</li>
<li><code>LightData</code>, a structure containing values specific to the light being
currently evaluated (see below)</li>
</ul>
<p>The <code>surfaceShading</code> function must return an RGB color in linear sRGB. Alpha
blending and alpha masking are handled outside of this function and must
therefore be ignored.</p>
<p>!!! Note: About shadowed fragments The <code>surfaceShading</code> function is invoked even
when a fragment is known to be fully in the shadow of the current light
(<code>lightData.NdotL &lt;= 0.0</code> or <code>lightData.visibility &lt;= 0.0</code>). This gives more
flexibility to the <code>surfaceShading</code> function as it provides a simple way to
handle constant ambient lighting for instance.</p>
<p>!!! Warning: Shading models Custom surface shading only works with the <code>lit</code>
shading model. Attempting to use any other model will result in an error.</p>
<h4 id="shading-data-structure"><a class="header" href="#shading-data-structure">Shading data structure</a></h4>
<pre><code class="language-glsl">struct ShadingData {
// The material's diffuse color, as derived from baseColor and metallic.
// This color is pre-multiplied by alpha and in the linear sRGB color space.
vec3 diffuseColor;
// The material's specular color, as derived from baseColor and metallic.
// This color is pre-multiplied by alpha and in the linear sRGB color space.
vec3 f0;
// The perceptual roughness is the roughness value set in MaterialInputs,
// with extra processing:
// - Clamped to safe values
// - Filtered if specularAntiAliasing is enabled
// This value is between 0.0 and 1.0.
float perceptualRoughness;
// The roughness value expected by BRDFs. This value is the square of
// perceptualRoughness. This value is between 0.0 and 1.0.
float roughness;
};
</code></pre>
<h4 id="light-data-structure"><a class="header" href="#light-data-structure">Light data structure</a></h4>
<pre><code class="language-glsl">struct LightData {
// The color (.rgb) and pre-exposed intensity (.w) of the light.
// The color is an RGB value in the linear sRGB color space.
// The pre-exposed intensity is the intensity of the light multiplied by
// the camera's exposure value.
vec4 colorIntensity;
// The normalized light vector, in world space (direction from the
// current fragment's position to the light).
vec3 l;
// The dot product of the shading normal (with normal mapping applied)
// and the light vector. This value is equal to the result of
// saturate(dot(getWorldSpaceNormal(), lightData.l)).
// This value is always between 0.0 and 1.0. When the value is &lt;= 0.0,
// the current fragment is not visible from the light and lighting
// computations can be skipped.
float NdotL;
// The position of the light in world space.
vec3 worldPosition;
// Attenuation of the light based on the distance from the current
// fragment to the light in world space. This value between 0.0 and 1.0
// is computed differently for each type of light (it's always 1.0 for
// directional lights).
float attenuation;
// Visibility factor computed from shadow maps or other occlusion data
// specific to the light being evaluated. This value is between 0.0 and
// 1.0.
float visibility;
};
</code></pre>
<h4 id="example-1"><a class="header" href="#example-1">Example</a></h4>
<p>The material below shows how to use custom surface shading to implement a
simplified toon shader:</p>
<pre><code class="language-glsl">material {
name : Toon,
shadingModel : lit,
parameters : [
{
type : float3,
name : baseColor
}
],
customSurfaceShading : true
}
fragment {
void material(inout MaterialInputs material) {
prepareMaterial(material);
material.baseColor.rgb = materialParams.baseColor;
}
vec3 surfaceShading(
const MaterialInputs materialInputs,
const ShadingData shadingData,
const LightData lightData
) {
// Number of visible shade transitions
const float shades = 5.0;
// Ambient intensity
const float ambient = 0.1;
float toon = max(ceil(lightData.NdotL * shades) / shades, ambient);
// Shadowing and attenuation
toon *= lightData.visibility * lightData.attenuation;
// Color and intensity
vec3 light = lightData.colorIntensity.rgb * lightData.colorIntensity.w;
return shadingData.diffuseColor * light * toon;
}
}
</code></pre>
<p>The result can be seen in figure [toonShading].</p>
<p><img src="images/screenshot_toon_shading.png" alt="Figure [toonShading]: simple toon shading implemented with custom surface shading" /></p>
<h2 id="shader-public-apis"><a class="header" href="#shader-public-apis">Shader public APIs</a></h2>
<h3 id="types"><a class="header" href="#types">Types</a></h3>
<p>While GLSL types can be used directly (<code>vec4</code> or <code>mat4</code>) we recommend the use of
the following type aliases:</p>
<div class="table-wrapper"><table><thead><tr><th style="text-align: left">Name</th><th style="text-align: center">GLSL type</th><th style="text-align: left">Description</th></tr></thead><tbody>
<tr><td style="text-align: left"><strong>bool2</strong></td><td style="text-align: center">bvec2</td><td style="text-align: left">A vector of 2 booleans</td></tr>
<tr><td style="text-align: left"><strong>bool3</strong></td><td style="text-align: center">bvec3</td><td style="text-align: left">A vector of 3 booleans</td></tr>
<tr><td style="text-align: left"><strong>bool4</strong></td><td style="text-align: center">bvec4</td><td style="text-align: left">A vector of 4 booleans</td></tr>
<tr><td style="text-align: left"><strong>int2</strong></td><td style="text-align: center">ivec2</td><td style="text-align: left">A vector of 2 integers</td></tr>
<tr><td style="text-align: left"><strong>int3</strong></td><td style="text-align: center">ivec3</td><td style="text-align: left">A vector of 3 integers</td></tr>
<tr><td style="text-align: left"><strong>int4</strong></td><td style="text-align: center">ivec4</td><td style="text-align: left">A vector of 4 integers</td></tr>
<tr><td style="text-align: left"><strong>uint2</strong></td><td style="text-align: center">uvec2</td><td style="text-align: left">A vector of 2 unsigned integers</td></tr>
<tr><td style="text-align: left"><strong>uint3</strong></td><td style="text-align: center">uvec3</td><td style="text-align: left">A vector of 3 unsigned integers</td></tr>
<tr><td style="text-align: left"><strong>uint4</strong></td><td style="text-align: center">uvec4</td><td style="text-align: left">A vector of 4 unsigned integers</td></tr>
<tr><td style="text-align: left"><strong>float2</strong></td><td style="text-align: center">float2</td><td style="text-align: left">A vector of 2 floats</td></tr>
<tr><td style="text-align: left"><strong>float3</strong></td><td style="text-align: center">float3</td><td style="text-align: left">A vector of 3 floats</td></tr>
<tr><td style="text-align: left"><strong>float4</strong></td><td style="text-align: center">float4</td><td style="text-align: left">A vector of 4 floats</td></tr>
<tr><td style="text-align: left"><strong>float4x4</strong></td><td style="text-align: center">mat4</td><td style="text-align: left">A 4x4 float matrix</td></tr>
<tr><td style="text-align: left"><strong>float3x3</strong></td><td style="text-align: center">mat3</td><td style="text-align: left">A 3x3 float matrix</td></tr>
</tbody></table>
</div>
<h3 id="math"><a class="header" href="#math">Math</a></h3>
<div class="table-wrapper"><table><thead><tr><th style="text-align: left">Name</th><th style="text-align: center">Type</th><th style="text-align: left">Description</th></tr></thead><tbody>
<tr><td style="text-align: left"><strong>PI</strong></td><td style="text-align: center">float</td><td style="text-align: left">A constant that represent \(\pi\)</td></tr>
<tr><td style="text-align: left"><strong>HALF_PI</strong></td><td style="text-align: center">float</td><td style="text-align: left">A constant that represent \(\frac{\pi}{2}\)</td></tr>
<tr><td style="text-align: left"><strong>saturate(float x)</strong></td><td style="text-align: center">float</td><td style="text-align: left">Clamps the specified value between 0.0 and 1.0</td></tr>
<tr><td style="text-align: left"><strong>pow5(float x)</strong></td><td style="text-align: center">float</td><td style="text-align: left">Computes \(x^5\)</td></tr>
<tr><td style="text-align: left"><strong>sq(float x)</strong></td><td style="text-align: center">float</td><td style="text-align: left">Computes \(x^2\)</td></tr>
<tr><td style="text-align: left"><strong>max3(float3 v)</strong></td><td style="text-align: center">float</td><td style="text-align: left">Returns the maximum value of the specified <code>float3</code></td></tr>
<tr><td style="text-align: left"><strong>mulMat4x4Float3(float4x4 m, float3 v)</strong></td><td style="text-align: center">float4</td><td style="text-align: left">Returns \(m * v\)</td></tr>
<tr><td style="text-align: left"><strong>mulMat3x3Float3(float4x4 m, float3 v)</strong></td><td style="text-align: center">float4</td><td style="text-align: left">Returns \(m * v\)+</td></tr>
</tbody></table>
</div>
<h3 id="matrices"><a class="header" href="#matrices">Matrices</a></h3>
<div class="table-wrapper"><table><thead><tr><th style="text-align: left">Name</th><th style="text-align: center">Type</th><th style="text-align: left">Description</th></tr></thead><tbody>
<tr><td style="text-align: left"><strong>getViewFromWorldMatrix()</strong></td><td style="text-align: center">float4x4</td><td style="text-align: left">Matrix that converts from world space to view/eye space</td></tr>
<tr><td style="text-align: left"><strong>getWorldFromViewMatrix()</strong></td><td style="text-align: center">float4x4</td><td style="text-align: left">Matrix that converts from view/eye space to world space</td></tr>
<tr><td style="text-align: left"><strong>getClipFromViewMatrix()</strong></td><td style="text-align: center">float4x4</td><td style="text-align: left">Matrix that converts from view/eye space to clip (NDC) space</td></tr>
<tr><td style="text-align: left"><strong>getViewFromClipMatrix()</strong></td><td style="text-align: center">float4x4</td><td style="text-align: left">Matrix that converts from clip (NDC) space to view/eye space</td></tr>
<tr><td style="text-align: left"><strong>getClipFromWorldMatrix()</strong></td><td style="text-align: center">float4x4</td><td style="text-align: left">Matrix that converts from world to clip (NDC) space</td></tr>
<tr><td style="text-align: left"><strong>getWorldFromClipMatrix()</strong></td><td style="text-align: center">float4x4</td><td style="text-align: left">Matrix that converts from clip (NDC) space to world space</td></tr>
</tbody></table>
</div>
<h3 id="frame-constants"><a class="header" href="#frame-constants">Frame constants</a></h3>
<div class="table-wrapper"><table><thead><tr><th style="text-align: left">Name</th><th style="text-align: center">Type</th><th style="text-align: left">Description</th></tr></thead><tbody>
<tr><td style="text-align: left"><strong>getResolution()</strong></td><td style="text-align: center">float4</td><td style="text-align: left">Dimensions of the view's effective (physical) viewport in pixels: <code>width</code>, <code>height</code>, <code>1 / width</code>, <code>1 / height</code>. This might be different from <code>View::getViewport()</code> for instance because of added rendering guard-bands.</td></tr>
<tr><td style="text-align: left"><strong>getWorldCameraPosition()</strong></td><td style="text-align: center">float3</td><td style="text-align: left">Position of the camera/eye in world space (see note below)</td></tr>
<tr><td style="text-align: left"><strong>getWorldOffset()</strong></td><td style="text-align: center">float3</td><td style="text-align: left">[deprecated] The shift required to obtain API-level world space. Use getUserWorldPosition() instead</td></tr>
<tr><td style="text-align: left"><strong>getUserWorldFromWorldMatrix()</strong></td><td style="text-align: center">float4x4</td><td style="text-align: left">Matrix that converts from world space to API-level (user) world space.</td></tr>
<tr><td style="text-align: left"><strong>getTime()</strong></td><td style="text-align: center">float</td><td style="text-align: left">Current time as a remainder of 1 second. Yields a value between 0 and 1</td></tr>
<tr><td style="text-align: left"><strong>getUserTime()</strong></td><td style="text-align: center">float4</td><td style="text-align: left">Current time in seconds: <code>time</code>, <code>(double)time - time</code>, <code>0</code>, <code>0</code></td></tr>
<tr><td style="text-align: left"><strong>getUserTimeMod(float m)</strong></td><td style="text-align: center">float</td><td style="text-align: left">Current time modulo m in seconds</td></tr>
<tr><td style="text-align: left"><strong>getExposure()</strong></td><td style="text-align: center">float</td><td style="text-align: left">Photometric exposure of the camera</td></tr>
<tr><td style="text-align: left"><strong>getEV100()</strong></td><td style="text-align: center">float</td><td style="text-align: left"><a href="https://en.wikipedia.org/wiki/Exposure_value">Exposure value at ISO 100</a> of the camera</td></tr>
</tbody></table>
</div>
<p>!!! TIP: world space To achieve good precision, the &quot;world space&quot; in Filament's
shading system does not necessarily match the API-level world space. To obtain
the position of the API-level camera, custom materials can use
<code>getUserWorldFromWorldMatrix()</code> to transform <code>getWorldCameraPosition()</code>.</p>
<h3 id="material-globals"><a class="header" href="#material-globals">Material globals</a></h3>
<div class="table-wrapper"><table><thead><tr><th style="text-align: left">Name</th><th style="text-align: center">Type</th><th style="text-align: left">Description</th></tr></thead><tbody>
<tr><td style="text-align: left"><strong>getMaterialGlobal0()</strong></td><td style="text-align: center">float4</td><td style="text-align: left">A vec4 visible by all materials, its value is set by <code>View::setMaterialGlobal(0, float4)</code>. Its default value is {0,0,0,1}.</td></tr>
<tr><td style="text-align: left"><strong>getMaterialGlobal1()</strong></td><td style="text-align: center">float4</td><td style="text-align: left">A vec4 visible by all materials, its value is set by <code>View::setMaterialGlobal(1, float4)</code>. Its default value is {0,0,0,1}.</td></tr>
<tr><td style="text-align: left"><strong>getMaterialGlobal2()</strong></td><td style="text-align: center">float4</td><td style="text-align: left">A vec4 visible by all materials, its value is set by <code>View::setMaterialGlobal(2, float4)</code>. Its default value is {0,0,0,1}.</td></tr>
<tr><td style="text-align: left"><strong>getMaterialGlobal3()</strong></td><td style="text-align: center">float4</td><td style="text-align: left">A vec4 visible by all materials, its value is set by <code>View::setMaterialGlobal(3, float4)</code>. Its default value is {0,0,0,1}.</td></tr>
</tbody></table>
</div>
<h3 id="vertex-only"><a class="header" href="#vertex-only">Vertex only</a></h3>
<p>The following APIs are only available from the vertex block:</p>
<div class="table-wrapper"><table><thead><tr><th style="text-align: left">Name</th><th style="text-align: center">Type</th><th style="text-align: left">Description</th></tr></thead><tbody>
<tr><td style="text-align: left"><strong>getPosition()</strong></td><td style="text-align: center">float4</td><td style="text-align: left">Vertex position in the domain defined by the material (default: object/model space)</td></tr>
<tr><td style="text-align: left"><strong>getCustom0()</strong> to <strong>getCustom7()</strong></td><td style="text-align: center">float4</td><td style="text-align: left">Custom vertex attribute</td></tr>
<tr><td style="text-align: left"><strong>getWorldFromModelMatrix()</strong></td><td style="text-align: center">float4x4</td><td style="text-align: left">Matrix that converts from model (object) space to world space</td></tr>
<tr><td style="text-align: left"><strong>getWorldFromModelNormalMatrix()</strong></td><td style="text-align: center">float3x3</td><td style="text-align: left">Matrix that converts normals from model (object) space to world space</td></tr>
<tr><td style="text-align: left"><strong>getVertexIndex()</strong></td><td style="text-align: center">int</td><td style="text-align: left">Index of the current vertex</td></tr>
</tbody></table>
</div>
<h3 id="fragment-only"><a class="header" href="#fragment-only">Fragment only</a></h3>
<p>The following APIs are only available from the fragment block:</p>
<div class="table-wrapper"><table><thead><tr><th style="text-align: left">Name</th><th style="text-align: center">Type</th><th style="text-align: left">Description</th></tr></thead><tbody>
<tr><td style="text-align: left"><strong>getWorldTangentFrame()</strong></td><td style="text-align: center">float3x3</td><td style="text-align: left">Matrix containing in each column the <code>tangent</code> (<code>frame[0]</code>), <code>bi-tangent</code> (<code>frame[1]</code>) and <code>normal</code> (<code>frame[2]</code>) of the vertex in world space. If the material does not compute a tangent space normal for bump mapping or if the shading is not anisotropic, only the <code>normal</code> is valid in this matrix.</td></tr>
<tr><td style="text-align: left"><strong>getWorldPosition()</strong></td><td style="text-align: center">float3</td><td style="text-align: left">Position of the fragment in world space (see note below about world-space)</td></tr>
<tr><td style="text-align: left"><strong>getUserWorldPosition()</strong></td><td style="text-align: center">float3</td><td style="text-align: left">Position of the fragment in API-level (user) world-space (see note below about world-space)</td></tr>
<tr><td style="text-align: left"><strong>getWorldViewVector()</strong></td><td style="text-align: center">float3</td><td style="text-align: left">Normalized vector in world space from the fragment position to the eye</td></tr>
<tr><td style="text-align: left"><strong>getWorldNormalVector()</strong></td><td style="text-align: center">float3</td><td style="text-align: left">Normalized normal in world space, after bump mapping (must be used after <code>prepareMaterial()</code>)</td></tr>
<tr><td style="text-align: left"><strong>getWorldGeometricNormalVector()</strong></td><td style="text-align: center">float3</td><td style="text-align: left">Normalized normal in world space, before bump mapping (can be used before <code>prepareMaterial()</code>)</td></tr>
<tr><td style="text-align: left"><strong>getWorldReflectedVector()</strong></td><td style="text-align: center">float3</td><td style="text-align: left">Reflection of the view vector about the normal (must be used after <code>prepareMaterial()</code>)</td></tr>
<tr><td style="text-align: left"><strong>getNormalizedViewportCoord()</strong></td><td style="text-align: center">float3</td><td style="text-align: left">Normalized user viewport position (i.e. NDC coordinates normalized to [0, 1] for the position, [1, 0] for the depth), can be used before <code>prepareMaterial()</code>). Because the user viewport is smaller than the actual physical viewport, these coordinates can be negative or superior to 1 in the non-visible area of the physical viewport.</td></tr>
<tr><td style="text-align: left"><strong>getNdotV()</strong></td><td style="text-align: center">float</td><td style="text-align: left">The result of <code>dot(normal, view)</code>, always strictly greater than 0 (must be used after <code>prepareMaterial()</code>)</td></tr>
<tr><td style="text-align: left"><strong>getColor()</strong></td><td style="text-align: center">float4</td><td style="text-align: left">Interpolated color of the fragment, if the color attribute is required</td></tr>
<tr><td style="text-align: left"><strong>getUV0()</strong></td><td style="text-align: center">float2</td><td style="text-align: left">First interpolated set of UV coordinates, only available if the uv0 attribute is required</td></tr>
<tr><td style="text-align: left"><strong>getUV1()</strong></td><td style="text-align: center">float2</td><td style="text-align: left">First interpolated set of UV coordinates, only available if the uv1 attribute is required</td></tr>
<tr><td style="text-align: left"><strong>getMaskThreshold()</strong></td><td style="text-align: center">float</td><td style="text-align: left">Returns the mask threshold, only available when <code>blending</code> is set to <code>masked</code></td></tr>
<tr><td style="text-align: left"><strong>inverseTonemap(float3)</strong></td><td style="text-align: center">float3</td><td style="text-align: left">Applies the inverse tone mapping operator to the specified linear sRGB color and returns a linear sRGB color. This operation may be an approximation and works best with the &quot;Filmic&quot; tone mapping operator</td></tr>
<tr><td style="text-align: left"><strong>inverseTonemapSRGB(float3)</strong></td><td style="text-align: center">float3</td><td style="text-align: left">Applies the inverse tone mapping operator to the specified non-linear sRGB color and returns a linear sRGB color. This operation may be an approximation and works best with the &quot;Filmic&quot; tone mapping operator</td></tr>
<tr><td style="text-align: left"><strong>luminance(float3)</strong></td><td style="text-align: center">float</td><td style="text-align: left">Computes the luminance of the specified linear sRGB color</td></tr>
<tr><td style="text-align: left"><strong>ycbcrToRgb(float, float2)</strong></td><td style="text-align: center">float3</td><td style="text-align: left">Converts a luminance and CbCr pair to a sRGB color</td></tr>
<tr><td style="text-align: left"><strong>uvToRenderTargetUV(float2)</strong></td><td style="text-align: center">float2</td><td style="text-align: left">Transforms a UV coordinate to allow sampling from a <code>RenderTarget</code> attachment</td></tr>
</tbody></table>
</div>
<p>!!! TIP: world-space To obtain API-level world-space coordinates, custom
materials should use <code>getUserWorldPosition()</code> or use
<code>getUserWorldFromWorldMatrix()</code>. Note that API-level world-space coordinates
should never or rarely be used because they may not fit in a float3 or have
severely reduced precision.</p>
<p>!!! TIP: sampling from render targets When sampling from a <code>filament::Texture</code>
that is attached to a <code>filament::RenderTarget</code> for materials in the surface
domain, please use <code>uvToRenderTargetUV</code> to transform the texture coordinate.
This will flip the coordinate depending on which backend is being used.</p>
<h1 id="compiling-materials"><a class="header" href="#compiling-materials">Compiling materials</a></h1>
<p>Material packages can be compiled from material definitions using the command
line tool called <code>matc</code>. The simplest way to use <code>matc</code> is to specify an input
material definition (<code>car_paint.mat</code> in the example below) and an output
material package (<code>car_paint.filamat</code> in the example below):</p>
<pre><code class="language-text">$ matc -o ./materials/bin/car_paint.filamat ./materials/src/car_paint.mat
</code></pre>
<h2 id="shader-validation"><a class="header" href="#shader-validation">Shader validation</a></h2>
<p><code>matc</code> attempts to validate shaders when compiling a material package. The
example below shows an example of an error message generated when compiling a
material definition containing a typo in the fragment shader (<code>metalic</code> instead
of <code>metallic</code>). The reported line numbers are line numbers in the source
material definition file.</p>
<pre><code class="language-text">ERROR: 0:13: 'metalic' : no such field in structure
ERROR: 0:13: '' : compilation terminated
ERROR: 2 compilation errors. No code generated.
Could not compile material metal.mat
</code></pre>
<h2 id="flags"><a class="header" href="#flags">Flags</a></h2>
<p>The command line flags relevant to application development are described in
table [matcFlags].</p>
<div class="table-wrapper"><table><thead><tr><th style="text-align: right">Flag</th><th style="text-align: center">Value</th><th style="text-align: left">Usage</th></tr></thead><tbody>
<tr><td style="text-align: right"><strong>-o</strong>, <strong>--output</strong></td><td style="text-align: center">[path]</td><td style="text-align: left">Specify the output file path</td></tr>
<tr><td style="text-align: right"><strong>-p</strong>, <strong>--platform</strong></td><td style="text-align: center">desktop/mobile/all</td><td style="text-align: left">Select the target platform(s)</td></tr>
<tr><td style="text-align: right"><strong>-a</strong>, <strong>--api</strong></td><td style="text-align: center">opengl/vulkan/all</td><td style="text-align: left">Specify the target graphics API</td></tr>
<tr><td style="text-align: right"><strong>-S</strong>, <strong>--optimize-size</strong></td><td style="text-align: center">N/A</td><td style="text-align: left">Optimize compiled material for size instead of just performance</td></tr>
<tr><td style="text-align: right"><strong>-r</strong>, <strong>--reflect</strong></td><td style="text-align: center">parameters</td><td style="text-align: left">Outputs the specified metadata as JSON</td></tr>
<tr><td style="text-align: right"><strong>-v</strong>, <strong>--variant-filter</strong></td><td style="text-align: center">[variant]</td><td style="text-align: left">Filters out the specified, comma-separated variants</td></tr>
</tbody></table>
</div>
<p>[Table [matcFlags]: List of <code>matc</code> flags]</p>
<p><code>matc</code> offers a few other flags that are irrelevant to application developers
and for internal use only.</p>
<h3 id="--platform"><a class="header" href="#--platform">--platform</a></h3>
<p>By default, <code>matc</code> generates material packages containing shaders for all
supported platforms. If you wish to reduce the size of your material packages,
it is recommended to select only the appropriate target platform. For instance,
to compile a material package for Android only, run the following command:</p>
<pre><code class="language-text">$ matc -p mobile -o ./materials/bin/car_paint.filamat ./materials/src/car_paint.mat
</code></pre>
<h3 id="--api"><a class="header" href="#--api">--api</a></h3>
<p>By default, <code>matc</code> generates material packages containing shaders for the OpenGL
API. You can choose to generate shaders for the Vulkan API in addition to the
OpenGL shaders. If you intend on targeting only Vulkan capable devices, you can
reduce the size of the material packages by generating only the set of Vulkan
shaders:</p>
<pre><code class="language-text">$ matc -a vulkan -o ./materials/bin/car_paint.filamat ./materials/src/car_paint.mat
</code></pre>
<h3 id="--optimize-size"><a class="header" href="#--optimize-size">--optimize-size</a></h3>
<p>This flag applies fewer optimization techniques to try and keep the final
material as small as possible. If the compiled material is deemed too large by
default, using this flag might be a good compromise between runtime performance
and size.</p>
<h3 id="--reflect"><a class="header" href="#--reflect">--reflect</a></h3>
<p>This flag was designed to help build tools around <code>matc</code>. It allows you to print
out specific metadata in JSON format. The example below prints out the list of
parameters defined in Filament's standard skybox material. It produces a list of
2 parameters, named <code>showSun</code> and <code>skybox</code>, respectively a boolean and a cubemap
texture.</p>
<pre><code class="language-text">$ matc --reflect parameters filament/src/materials/skybox.mat
{
&quot;parameters&quot;: [
{
&quot;name&quot;: &quot;showSun&quot;,
&quot;type&quot;: &quot;bool&quot;,
&quot;size&quot;: &quot;1&quot;
},
{
&quot;name&quot;: &quot;skybox&quot;,
&quot;type&quot;: &quot;samplerCubemap&quot;,
&quot;format&quot;: &quot;float&quot;,
&quot;precision&quot;: &quot;default&quot;
}
]
}
</code></pre>
<h3 id="--variant-filter"><a class="header" href="#--variant-filter">--variant-filter</a></h3>
<p>This flag can be used to further reduce the size of a compiled material. It is
used to specify a list of shader variants that the application guarantees will
never be needed. These shader variants are skipped during the code generation
phase of <code>matc</code>, thus reducing the overall size of the material.</p>
<p>The variants must be specified as a comma-separated list, using one of the
following available variants:</p>
<ul>
<li><code>directionalLighting</code>, used when a directional light is present in the scene</li>
<li><code>dynamicLighting</code>, used when a non-directional light (point, spot, etc.) is
present in the scene</li>
<li><code>shadowReceiver</code>, used when an object can receive shadows</li>
<li><code>skinning</code>, used when an object is animated using GPU skinning or vertex
morphing</li>
<li><code>fog</code>, used when global fog is applied to the scene</li>
<li><code>vsm</code>, used when VSM shadows are enabled and the object is a shadow receiver</li>
<li><code>ssr</code>, used when screen-space reflections are enabled in the View</li>
</ul>
<p>Example: <code>--variant-filter=skinning,shadowReceiver</code></p>
<p>Note that some variants may automatically be filtered out. For instance, all
lighting related variants (<code>directionalLighting</code>, etc.) are filtered out when
compiling an <code>unlit</code> material.</p>
<p>When this flag is used, the specified variant filters are merged with the
variant filters specified in the material itself.</p>
<p>Use this flag with caution, filtering out a variant required at runtime may lead
to crashes.</p>
<h1 id="handling-colors"><a class="header" href="#handling-colors">Handling colors</a></h1>
<h2 id="linear-colors"><a class="header" href="#linear-colors">Linear colors</a></h2>
<p>If the color data comes from a texture, simply make sure you use an sRGB texture
to benefit from automatic hardware conversion from sRGB to linear. If the color
data is passed as a parameter to the material you can convert from sRGB to
linear by running the following algorithm on each color channel:</p>
<pre><code class="language-glsl">float sRGB_to_linear(float color) {
return color &lt;= 0.04045 ? color / 12.92 : pow((color + 0.055) / 1.055, 2.4);
}
</code></pre>
<p>Alternatively you can use one of the two cheaper but less accurate versions
shown below:</p>
<pre><code class="language-glsl">// Cheaper
linearColor = pow(color, 2.2);
// Cheapest
linearColor = color * color;
</code></pre>
<h2 id="pre-multiplied-alpha"><a class="header" href="#pre-multiplied-alpha">Pre-multiplied alpha</a></h2>
<p>A color uses pre-multiplied alpha if its RGB components are multiplied by the
alpha channel:</p>
<pre><code class="language-glsl">// Compute pre-multiplied color
color.rgb *= color.a;
</code></pre>
<p>If the color is sampled from a texture, you can simply ensure that the texture
data is pre-multiplied ahead of time. On Android, any texture uploaded from a
<a href="https://developer.android.com/reference/android/graphics/Bitmap.html">Bitmap</a>
will be pre-multiplied by default.</p>
<h1 id="sampler-usage-in-materials"><a class="header" href="#sampler-usage-in-materials">Sampler usage in Materials</a></h1>
<p>The number of usable sampler parameters (e.g.: type is <code>sampler2d</code>) in materials
is limited and depends on the material properties, shading model, feature level
and variant filter.</p>
<h2 id="feature-level-1-and-2"><a class="header" href="#feature-level-1-and-2">Feature level 1 and 2</a></h2>
<p><code>unlit</code> materials can use up to 12 samplers by default.</p>
<p><code>lit</code> materials can use up to 9 samplers by default, however if <code>refractionMode</code>
or <code>reflectionMode</code> is set to <code>screenspace</code> that number is reduced to 8.</p>
<p>Finally if <code>variantFilter</code> contains the <code>fog</code> filter, an extra sampler is made
available, such that <code>unlit</code> materials can use up to 13 and <code>lit</code> materials up
to 10 samplers by default.</p>
<h2 id="feature-level-3"><a class="header" href="#feature-level-3">Feature level 3</a></h2>
<p>16 samplers are available.</p>
<p>!!! TIP: external samplers Be aware that <code>external</code> samplers account for 2
regular samplers.</p>
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