sheen #2348
Description
GLTF
https://github.com/KhronosGroup/glTF/tree/main/extensions/2.0/Khronos/KHR_materials_sheen
three.js
babylon
技术细节
直接光部分：
https://github.com/BabylonJS/Babylon.js/blob/7fd025d4fbb4ea0b6f4f108788cd312a613b38d8/packages/dev/core/src/Shaders/ShadersInclude/pbrDirectLightingFunctions.fx#L160
间接光部分：
https://github.com/BabylonJS/Babylon.js/blob/7fd025d4fbb4ea0b6f4f108788cd312a613b38d8/packages/dev/core/src/Shaders/ShadersInclude/pbrBlockSheen.fx#L42
filament
float distributionCloth(float roughness, float NoH) {
#if BRDF_CLOTH_D == SPECULAR_D_CHARLIE
return D_Charlie(roughness, NoH);
#endif
}
float visibilityCloth(float NoV, float NoL) {
#if BRDF_CLOTH_V == SPECULAR_V_NEUBELT
return V_Neubelt(NoV, NoL);
#endif
}
#if defined(MATERIAL_HAS_SHEEN_COLOR)
vec3 sheenLobe(const PixelParams pixel, float NoV, float NoL, float NoH) {
float D = distributionCloth(pixel.sheenRoughness, NoH);
float V = visibilityCloth(NoV, NoL);
return (D * V) * pixel.sheenColor;
}
#endif
技术对比
sheen由于没什么特别难的算法，所以三个引擎都使用了基本相同的brdf算法，只是一些api调用不太一样
方案
按照sheen标准brdf算法内置到引擎，uniform一一对应GLTF2.0标准。