72 lines
1.7 KiB
HLSL
72 lines
1.7 KiB
HLSL
static const float PI = 3.141592653589793;
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float3 FresnelSchlick(float cosTheta, float3 F0)
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{
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return F0 + (1.0 - F0) * pow(1.0 - cosTheta, 5.0);
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}
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float DistributionGGX(float3 N, float3 H, float roughness)
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{
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float a = roughness * roughness;
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float a2 = a * a;
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float NdotH = max(dot(N, H), 0.0);
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float NdotH2 = NdotH * NdotH;
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float num = a2;
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float denom = (NdotH2 * (a2 - 1.0) + 1.0);
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denom = PI * denom * denom;
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return num / denom;
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}
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float GeometrySchlickGGX(float NdotV, float roughness)
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{
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float r = (roughness + 1.0);
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float k = (r * r) / 8.0;
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float num = NdotV;
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float denom = NdotV * (1.0 - k) + k;
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return num / denom;
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}
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float GeometrySmith(float3 N, float3 V, float3 L, float roughness)
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{
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float NdotV = max(dot(N, V), 0.0);
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float NdotL = max(dot(N, L), 0.0);
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float ggx2 = GeometrySchlickGGX(NdotV, roughness);
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float ggx1 = GeometrySchlickGGX(NdotL, roughness);
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return ggx1 * ggx2;
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}
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float3 ComputeLight(
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float3 L,
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float3 radiance,
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float3 F0,
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float3 V,
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float3 N,
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float3 albedo,
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float metallic,
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float roughness,
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float visibility
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) {
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float3 H = normalize(V + L);
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float NDF = DistributionGGX(N, H, roughness);
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float G = GeometrySmith(N, V, L, roughness);
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float3 F = FresnelSchlick(max(dot(H, V), 0.0), F0);
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float3 numerator = NDF * G * F;
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float denominator = 4.0 * max(dot(N, V), 0.0) * max(dot(N, L), 0.0);
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float3 specular = numerator / max(denominator, 0.001);
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float3 kS = F;
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float3 kD = float3(1.0, 1.0, 1.0) - kS;
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kD *= 1.0 - metallic;
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float NdotL = max(dot(N, L), 0.0);
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return (kD * albedo / PI + specular) * radiance * NdotL * visibility;
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}
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