// Reminder: This is a static if resolve at compile time
if (HasFlag(bsdfData.materialFeatures, MATERIALFEATUREFLAGS_CLOTH_SILK))
{
GetPreIntegratedFGDGGXAndDisneyDiffuse(NdotV, preLightData.iblPerceptualRoughness, bsdfData.fresnel0, preLightData.specularFGD, preLightData.diffuseFGD, unused);
// For GGX aniso and IBL we have done an empirical (eye balled) approximation compare to the reference.
// We use a single fetch, and we stretch the normal to use based on various criteria.
// result are far away from the reference but better than nothing
// For positive anisotropy values: tangent = highlight stretch (anisotropy) direction, bitangent = grain (brush) direction.
float3 grainDirWS = (bsdfData.anisotropy >= 0.0) ? bsdfData.bitangentWS : bsdfData.tangentWS;
// Reduce stretching for (perceptualRoughness < 0.2).
float stretch = abs(bsdfData.anisotropy) * saturate(5 * preLightData.iblPerceptualRoughness);
// NOTE: If we follow the theory we should use the modified normal for the different calculation implying a normal (like NdotV) and use 'anisoIblNormalWS'
// into function like GetSpecularDominantDir(). However modified normal is just a hack. The goal is just to stretch a cubemap, no accuracy here.
// With this in mind and for performance reasons we chose to only use modified normal to calculate R.
iblN = GetAnisotropicModifiedNormal(grainDirWS, N, V, stretch);
GetPreIntegratedFGDGGXAndDisneyDiffuse(NdotV, preLightData.iblPerceptualRoughness, bsdfData.fresnel0, preLightData.specularFGD, preLightData.diffuseFGD, unused);
// This is a ad-hoc tweak to better match reference of anisotropic GGX.
// TODO: We need a better hack.
preLightData.iblPerceptualRoughness *= saturate(1.2 - abs(bsdfData.anisotropy));
// perceptualRoughness is use as input and output here
GetGGXAnisotropicModifiedNormalAndRoughness(bsdfData.bitangentWS, bsdfData.tangentWS, N, V, bsdfData.anisotropy, preLightData.iblPerceptualRoughness, iblN, preLightData.iblPerceptualRoughness);
}
else
{
Anis Benyoub