Cycles: Fix excessive sampling weight of glossy Principled BSDF components

If there was any specularity in the Principled BSDF, it would get a sampling
weight of one regardless of its actual impact.

This commit makes Cycles estimate the contribution of the component and adjust
the weighting accordingly, which greatly improves the noise characteristics of
the Principled BSDF in many cases.

Note that this commit might slightly change the brightness of areas when using
MultiGGX and high roughnesses, but the new brightness is more accurate and
closer to the result of Branched Path Tracing. See T51836 for details.

Differential Revision: https://developer.blender.org/D2677

1 files changed, 6 insertions, 6 deletions

diff --git a/intern/cycles/kernel/osl/osl_closures.cpp b/intern/cycles/kernel/osl/osl_closures.cpp
index f76fc0d6fea..2f0897434ec 100644
--- a/intern/cycles/kernel/osl/osl_closures.cpp
+++ b/intern/cycles/kernel/osl/osl_closures.cpp
@@ -217,7 +217,7 @@ public:
 	void setup(ShaderData *sd, int path_flag, float3 weight)
 	{
 		MicrofacetBsdf *bsdf = alloc(sd, path_flag, weight);
-		sd->flag |= (bsdf) ? bsdf_microfacet_ggx_clearcoat_setup(bsdf) : 0;
+		sd->flag |= (bsdf) ? bsdf_microfacet_ggx_clearcoat_setup(bsdf, sd) : 0;
 	}
 };
 
@@ -389,7 +389,7 @@ public:
 	void setup(ShaderData *sd, int path_flag, float3 weight)
 	{
 		MicrofacetBsdf *bsdf = alloc(sd, path_flag, weight);
-		sd->flag |= (bsdf) ? bsdf_microfacet_ggx_fresnel_setup(bsdf) : 0;
+		sd->flag |= (bsdf) ? bsdf_microfacet_ggx_fresnel_setup(bsdf, sd) : 0;
 	}
 };
 
@@ -413,7 +413,7 @@ public:
 	void setup(ShaderData *sd, int path_flag, float3 weight)
 	{
 		MicrofacetBsdf *bsdf = alloc(sd, path_flag, weight);
-		sd->flag |= (bsdf) ? bsdf_microfacet_ggx_aniso_fresnel_setup(bsdf) : 0;
+		sd->flag |= (bsdf) ? bsdf_microfacet_ggx_aniso_fresnel_setup(bsdf, sd) : 0;
 	}
 };
 
@@ -566,7 +566,7 @@ public:
 	void setup(ShaderData *sd, int path_flag, float3 weight)
 	{
 		MicrofacetBsdf *bsdf = alloc(sd, path_flag, weight);
-		sd->flag |= (bsdf) ? bsdf_microfacet_multi_ggx_fresnel_setup(bsdf) : 0;
+		sd->flag |= (bsdf) ? bsdf_microfacet_multi_ggx_fresnel_setup(bsdf, sd) : 0;
 	}
 };
 
@@ -590,7 +590,7 @@ public:
 	void setup(ShaderData *sd, int path_flag, float3 weight)
 	{
 		MicrofacetBsdf *bsdf = alloc(sd, path_flag, weight);
-		sd->flag |= (bsdf) ? bsdf_microfacet_multi_ggx_aniso_fresnel_setup(bsdf) : 0;
+		sd->flag |= (bsdf) ? bsdf_microfacet_multi_ggx_aniso_fresnel_setup(bsdf, sd) : 0;
 	}
 };
 
@@ -618,7 +618,7 @@ public:
 	void setup(ShaderData *sd, int path_flag, float3 weight)
 	{
 		MicrofacetBsdf *bsdf = alloc(sd, path_flag, weight);
-		sd->flag |= (bsdf) ? bsdf_microfacet_multi_ggx_glass_fresnel_setup(bsdf) : 0;
+		sd->flag |= (bsdf) ? bsdf_microfacet_multi_ggx_glass_fresnel_setup(bsdf, sd) : 0;
 	}
 };