Mathias Agopian 167a91efaa Optimize Shader LineDictionary (#9814)
* Optimize Shader LineDictionary with Variable-Length 3-Streams

This commit completely reorganizes the string dictionary compression
pipeline used by compiled Material Text Chunks and improves matinfo
dictionary output.

1. Multi-Base Variable-Length Scaling:
We replaced the static 16-bit indices overhead with a
bounded payload. Now, indices scale dynamically:
- 0 to 239 evaluate in 1 byte.
- 240 to 3584 leverage 0xF0-0xFD escapes evaluating in 2 bytes.
- 3584+ are locked behind a 0xFF marker to 3 bytes.
This natively eradicated the massive monolithic lengths and zero-padding
issues previously dominating shader packages.

2. Variable-Length 3-Stream Decoding:
To solve the Zstandard/Zlib entropy fragmentation that conventionally
plagues interleaved variable byte lengths (which previously inflated
our `filament.aar` boundary constraint by +2KB), we segregated the encoded
payloads.

By grouping high-entropy string boundaries into a `Base Stream`
and isolating offset digits inside an `Extension Stream`,
predictive LZ77 ZIP sliding-windows perfectly map
over both arrays independently without disruption.

3. Optimize Numeric Stream using LEB128
Prior to this change, numerical suffixes split from shader
variables (e.g., `param_1024` -> `param_` + `1024`) were fed back
into the localized String Dictionary. Because high-frequency numbers were
assigned disjointed localized IDs per shader variant, LZ77
failed to cross-reference their repetitive structures across
shipped `.aar` archives, fracturing compression sequences.

This patch implements a unified 3-Stream topology. It
extracts numerical primitives (< 32768) away from the baseline
String Dictionary, writing them into an isolated, contiguous
LEB128 array.

By using a dedicated `[254]` Escape Token within the primary stream, numerical
variables maintain exact 1-byte (`< 128`) or 2-byte (`>= 128`)
geometric layouts across all permutations.

The resulting deterministic alignment guarantees that Zlib sliding windows
can deduplicate highly repetitive variables across the
entire application binary block.

4. We use the ShaderStage information to create distinct index ranges, which
further help use 1-byte indices.

Verification Metrics:
 `filament-android.aar`: -7,938 B
 `gltfio-android.aar`: -290,939 B
 `libfilament.a`: -18,464 B

* Optimize shader dictionary by decoding '_' for numeric literals

Most numbers extracted from the shader text are preceded by an 
underscore (e.g., from `_`, `hp_copy_`), which previously caused 
standalone `_` strings to heavily pollute the LineDictionary.

This change removes the standalone `_` from the dictionary index:
- `MaterialChunk` rehydrates the `_` prefix when decoding these numeric
literals.

This frees up dictionary indices, yielding massive byte savings across 
uncompressed binaries (e.g., -28.4 KB for volume_masked.filamat).

* Optimize ShaderMinifier to strip explicit spacing

Spirv-cross outputs GLSL with explicit spacing around generic
operators (e.g., ` = `, `, `, ` ) * `). This padding consumes a 
significant amount of uncompressed bytes across large ubershaders. 

By applying targeted string replacements at the end of the `ShaderMinifier` 
pass, we strip this extraneous padding down to its raw tokens 
(e.g., `a=b`, `a,b`, `a*b`). 

This optimization preserves isolating spaces where valuable, ensuring 
line-dictionary tokens (such as raw `=` or `,`)  remain deduplicated 
instead of fusing into unpredictable variables. 

Impact:
This saves roughly ~9.1 KB in `libfilament.a` and ~3.2 KB in 
`volume_masked.filamat` uncompressed, with proportional gains across 
the downstream LZ4 compressed archives.
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Filament

Android Build Status iOS Build Status Linux Build Status macOS Build Status Windows Build Status Web Build Status

Filament is a real-time physically based rendering engine for Android, iOS, Linux, macOS, Windows, and WebGL. It is designed to be as small as possible and as efficient as possible on Android.

Download

Download Filament releases to access stable builds. Filament release archives contains host-side tools that are required to generate assets.

Make sure you always use tools from the same release as the runtime library. This is particularly important for matc (material compiler).

If you'd rather build Filament yourself, please refer to our build manual.

Android

Android projects can simply declare Filament libraries as Maven dependencies:

repositories {
    // ...
    mavenCentral()
}

dependencies {
    implementation 'com.google.android.filament:filament-android:1.70.1'
}

Here are all the libraries available in the group com.google.android.filament:

Artifact Description
filament-android The Filament rendering engine itself.
filament-android-debug Debug version of filament-android.
gltfio-android A glTF 2.0 loader for Filament, depends on filament-android.
filament-utils-android KTX loading, Kotlin math, and camera utilities, depends on gltfio-android.
filamat-android A runtime material builder/compiler. This library is large but contains a full shader compiler/validator/optimizer and supports both OpenGL and Vulkan.

iOS

iOS projects can use CocoaPods to install the latest release:

pod 'Filament', '~> 1.70.1'

Documentation

  • Filament, an in-depth explanation of real-time physically based rendering, the graphics capabilities and implementation of Filament. This document explains the math and reasoning behind most of our decisions. This document is a good introduction to PBR for graphics programmers.
  • Materials, the full reference documentation for our material system. This document explains our different material models, how to use the material compiler matc and how to write custom materials.
  • Material Properties, a reference sheet for the standard material model.

Examples

Night scene Night scene Materials Materials Helmet Screen-space refraction

Features

APIs

  • Native C++ API for Android, iOS, Linux, macOS and Windows
  • Java/JNI API for Android
  • JavaScript API

Backends

  • OpenGL 4.1+ for Linux, macOS and Windows
  • OpenGL ES 3.0+ for Android and iOS
  • Metal for macOS and iOS
  • Vulkan 1.0 for Android, Linux, macOS, and Windows
  • WebGPU for Android, Linux, macOS, and Windows
  • WebGL 2.0 for all browsers supporting it

Rendering

  • Clustered forward renderer
  • Cook-Torrance microfacet specular BRDF
  • Lambertian diffuse BRDF
  • Custom lighting/surface shading
  • HDR/linear lighting
  • Metallic workflow
  • Clear coat
  • Anisotropic lighting
  • Approximated translucent (subsurface) materials
  • Cloth/fabric/sheen shading
  • Normal mapping & ambient occlusion mapping
  • Image-based lighting
  • Physically-based camera (shutter speed, sensitivity and aperture)
  • Physical light units
  • Point lights, spot lights, and directional light
  • Specular anti-aliasing
  • Point, spot, and directional light shadows
  • Cascaded shadows
  • EVSM, PCSS, DPCF, or PCF shadows
  • Transparent shadows
  • Contact shadows
  • Screen-space ambient occlusion
  • Screen-space reflections
  • Screen-space refraction
  • Global fog
  • Dynamic resolution (with support for AMD FidelityFX FSR)

Post processing

  • HDR bloom
  • Depth of field bokeh
  • Multiple tone mappers: PBR Neutral, AgX, generic (customizable), ACES, filmic, etc.
  • Color and tone management: luminance scaling, gamut mapping
  • Color grading: exposure, night adaptation, white balance, channel mixer, shadows/mid-tones/highlights, ASC CDL, contrast, saturation, etc.
  • TAA, FXAA, MSAA
  • Screen-space lens flares

glTF 2.0

  • Encodings

    • Embeded
    • Binary
  • Primitive Types

    • Points
    • Lines
    • Line Loop
    • Line Strip
    • Triangles
    • Triangle Strip
    • Triangle Fan
  • Animation

    • Transform animation
    • Linear interpolation
    • Morph animation
      • Sparse accessor
    • Skin animation
    • Joint animation
  • Extensions

    • KHR_draco_mesh_compression
    • KHR_lights_punctual
    • KHR_materials_clearcoat
    • KHR_materials_dispersion
    • KHR_materials_emissive_strength
    • KHR_materials_ior
    • KHR_materials_pbrSpecularGlossiness
    • KHR_materials_sheen
    • KHR_materials_specular
    • KHR_materials_transmission
    • KHR_materials_unlit
    • KHR_materials_variants
    • KHR_materials_volume
    • KHR_mesh_quantization
    • KHR_texture_basisu
    • KHR_texture_transform
    • EXT_meshopt_compression

Rendering with Filament

Native Linux, macOS and Windows

You must create an Engine, a Renderer and a SwapChain. The SwapChain is created from a native window pointer (an NSView on macOS or a HWND on Windows for instance):

Engine* engine = Engine::create();
SwapChain* swapChain = engine->createSwapChain(nativeWindow);
Renderer* renderer = engine->createRenderer();

To render a frame you must then create a View, a Scene and a Camera:

Camera* camera = engine->createCamera(EntityManager::get().create());
View* view = engine->createView();
Scene* scene = engine->createScene();

view->setCamera(camera);
view->setScene(scene);

Renderables are added to the scene:

Entity renderable = EntityManager::get().create();
// build a quad
RenderableManager::Builder(1)
        .boundingBox({{ -1, -1, -1 }, { 1, 1, 1 }})
        .material(0, materialInstance)
        .geometry(0, RenderableManager::PrimitiveType::TRIANGLES, vertexBuffer, indexBuffer, 0, 6)
        .culling(false)
        .build(*engine, renderable);
scene->addEntity(renderable);

The material instance is obtained from a material, itself loaded from a binary blob generated by matc:

Material* material = Material::Builder()
        .package((void*) BAKED_MATERIAL_PACKAGE, sizeof(BAKED_MATERIAL_PACKAGE))
        .build(*engine);
MaterialInstance* materialInstance = material->createInstance();

To learn more about materials and matc, please refer to the materials documentation.

To render, simply pass the View to the Renderer:

// beginFrame() returns false if we need to skip a frame
if (renderer->beginFrame(swapChain)) {
    // for each View
    renderer->render(view);
    renderer->endFrame();
}

For complete examples of Linux, macOS and Windows Filament applications, look at the source files in the samples/ directory. These samples are all based on libs/filamentapp/ which contains the code that creates a native window with SDL2 and initializes the Filament engine, renderer and views.

For more information on how to prepare environment maps for image-based lighting please refer to BUILDING.md.

Android

See android/samples for examples of how to use Filament on Android.

You must always first initialize Filament by calling Filament.init().

Rendering with Filament on Android is similar to rendering from native code (the APIs are largely the same across languages). You can render into a Surface by passing a Surface to the createSwapChain method. This allows you to render to a SurfaceTexture, a TextureView or a SurfaceView. To make things easier we provide an Android specific API called UiHelper in the package com.google.android.filament.android. All you need to do is set a render callback on the helper and attach your SurfaceView or TextureView to it. You are still responsible for creating the swap chain in the onNativeWindowChanged() callback.

iOS

Filament is supported on iOS 11.0 and above. See ios/samples for examples of using Filament on iOS.

Filament on iOS is largely the same as native rendering with C++. A CAEAGLLayer or CAMetalLayer is passed to the createSwapChain method. Filament for iOS supports both Metal (preferred) and OpenGL ES.

Assets

To get started you can use the textures and environment maps found respectively in third_party/textures and third_party/environments. These assets are under CC0 license. Please refer to their respective URL.txt files to know more about the original authors.

Environments must be pre-processed using cmgen or using the libiblprefilter library.

How to make contributions

Please read and follow the steps in CONTRIBUTING.md. Make sure you are familiar with the code style.

Directory structure

This repository not only contains the core Filament engine, but also its supporting libraries and tools.

  • android: Android libraries and projects
    • filamat-android: Filament material generation library (AAR) for Android
    • filament-android: Filament library (AAR) for Android
    • filament-utils-android: Extra utilities (KTX loader, math types, etc.)
    • gltfio-android: Filament glTF loading library (AAR) for Android
    • samples: Android-specific Filament samples
  • art: Source for various artworks (logos, PDF manuals, etc.)
  • assets: 3D assets to use with sample applications
  • build: CMake build scripts
  • docs: Documentation
    • math: Mathematica notebooks used to explore BRDFs, equations, etc.
  • filament: Filament rendering engine (minimal dependencies)
    • backend: Rendering backends/drivers (Vulkan, Metal, OpenGL/ES)
  • ide: Configuration files for IDEs (CLion, etc.)
  • ios: Sample projects for iOS
  • libs: Libraries
    • bluegl: OpenGL bindings for macOS, Linux and Windows
    • bluevk: Vulkan bindings for macOS, Linux, Windows and Android
    • camutils: Camera manipulation utilities
    • filabridge: Library shared by the Filament engine and host tools
    • filaflat: Serialization/deserialization library used for materials
    • filagui: Helper library for Dear ImGui
    • filamat: Material generation library
    • filamentapp: SDL2 skeleton to build sample apps
    • filameshio: Tiny filamesh parsing library (see also tools/filamesh)
    • geometry: Mesh-related utilities
    • gltfio: Loader for glTF 2.0
    • ibl: IBL generation tools
    • image: Image filtering and simple transforms
    • imageio: Image file reading / writing, only intended for internal use
    • matdbg: DebugServer for inspecting shaders at run-time (debug builds only)
    • math: Math library
    • mathio: Math types support for output streams
    • utils: Utility library (threads, memory, data structures, etc.)
    • viewer: glTF viewer library (requires gltfio)
  • samples: Sample desktop applications
  • shaders: Shaders used by filamat and matc
  • third_party: External libraries and assets
    • environments: Environment maps under CC0 license that can be used with cmgen
    • models: Models under permissive licenses
    • textures: Textures under CC0 license
  • tools: Host tools
    • cmgen: Image-based lighting asset generator
    • filamesh: Mesh converter
    • glslminifier: Minifies GLSL source code
    • matc: Material compiler
    • matedit: Material editor for compiled materials
    • matinfo Displays information about materials compiled with matc
    • mipgen Generates a series of miplevels from a source image
    • normal-blending: Tool to blend normal maps
    • resgen Aggregates binary blobs into embeddable resources
    • roughness-prefilter: Pre-filters a roughness map from a normal map to reduce aliasing
    • specular-color: Computes the specular color of conductors based on spectral data
  • web: JavaScript bindings, documentation, and samples

License

Please see LICENSE.

Disclaimer

This is not an officially supported Google product.

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