* Materials can now specify a shadow strength factor
Materials have a new property: shadowStrength that can be used to
attenuate all shadows received by this material. e.g.:
```
void material(inout MaterialInputs material) {
prepareMaterial(material);
material. shadowStrength = 0.1;
}
```
FIXES=[391663042]
Co-authored-by: Powei Feng <powei@google.com>
---------
Co-authored-by: Powei Feng <powei@google.com>
This adds a new material property (float postLightingMixFactor) which
is used to mix the original color with the post-lighting blended color.
The default value is 1.0, which keeps the current behavior.
FIXES=[328498606]
* check that user materials don't exceed their allowed features
* backend sampler limits now take feature level into account
- in the backend, the constants are now in an array indexed by the
feature level
- samplerBindingMap now asserts only what it can.
- matc (filamat) now logs the user samplers when an error is detected.
* API CHANGE: honor user-defined precision, rename SamplerPrecision.
matc now honors 'precision' on non-samplers in mat files, and
the filamat API now allows clients to specify precision for
non-samplers.
This involved flattening a union that is internal to filamat.
* MaterialBuilder: Add Java bindings for precision.
* Add support for sheenColor and sheenRoughness
This work is necessary to support the glTF extension KHR_materials_sheen.
This change effectively adds the specular lobe from the cloth material
model to the base material model. The cloth model remains useful for
its extra subsurface color feature but also because it's cheaper.
* Add support for KHR_materials_sheen to gltfio
* Update documentation
* Document default shading values
* Add support for bent normals
Bent normals can be enabled via the bentNormal property of a material.
When specular occlusion is enabled, bent normals improve the quality
of the computation.
* Save a couple of multiplications in bent specular AO
When dealing with thin objects we really have two thicknesses to
consider, the thickness in the direction of the normal, which
corresponds to the value used for solid objects, and the thickness of
the object's walls, which generally is a constant.
Reusing thickness in the later case is problematic for assets that have
a thickness map, but are rendered hollow.
In the future we can even imagine handling double-sided hollow objects
by using the thickness information -- e.g. a hollow cube.
Normally the IOR is deduced from the reflectance, but now we allow to
specify the IOR instead or in addition to the reflectance.
In the later case, it's possible to create physically impossible
materials, but this can be useful for artistic reasons.
* Add the ability to modify clip space coordinates in the vertex shader
This introduces MaterialVertexInputs.clipSpaceTransform, a mat4 that
is applied to gl_Position before exiting the vertex stage.
* Address code review comments
* Add postLightingColor property to materials
This property can be used to modify the color computed in the lighting
passes of the materials. That color is blended with the computed color
according to the postLightingBlending option (add, transparent or opaque).
* Remove test
* Update docs
* Address code review comment
* Switch postLightingColor default blend mode to transparent
