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23 行
1.1 KiB
23 行
1.1 KiB
TEXTURE2D(_PreIntegratedFGD);
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// For image based lighting, a part of the BSDF is pre-integrated.
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// This is done both for specular GGX height-correlated and DisneyDiffuse
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// reflectivity is Integral{(BSDF_GGX / F) - use for multiscattering
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void GetPreIntegratedFGDGGXAndDisneyDiffuse(float NdotV, float perceptualRoughness, float3 fresnel0, out float3 GGXSpecularFGD, out float disneyDiffuseFGD, out float reflectivity)
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{
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float3 preFGD = SAMPLE_TEXTURE2D_LOD(_PreIntegratedFGD, s_linear_clamp_sampler, float2(NdotV, perceptualRoughness), 0).xyz;
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// Pre-integrate GGX FGD
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// Integral{BSDF * <N,L> dw} =
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// Integral{(F0 + (1 - F0) * (1 - <V,H>)^5) * (BSDF / F) * <N,L> dw} =
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// (1 - F0) * Integral{(1 - <V,H>)^5 * (BSDF / F) * <N,L> dw} + F0 * Integral{(BSDF / F) * <N,L> dw}=
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// (1 - F0) * x + F0 * y = lerp(x, y, F0)
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GGXSpecularFGD = lerp(preFGD.xxx, preFGD.yyy, fresnel0);
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// Pre integrate DisneyDiffuse FGD:
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// z = DisneyDiffuse
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// Remap from the [0, 1] to the [0.5, 1.5] range.
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disneyDiffuseFGD = preFGD.z + 0.5;
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reflectivity = preFGD.y;
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}
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