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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
This commit is contained in:
Lukas Stockner 2017-06-21 02:57:58 +02:00
parent 8cb741a598
commit 1979176088
Notes: blender-bot 2023-02-14 06:52:11 +01:00 
Referenced by issue #51867, I - L / I - R / I - S key combos are broken
4 changed files with 41 additions and 17 deletions
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18
intern/cycles/kernel/closure/bsdf_microfacet.h
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@ -288,12 +288,16 @@ ccl_device int bsdf_microfacet_ggx_setup(MicrofacetBsdf *bsdf)
return SD_BSDF|SD_BSDF_HAS_EVAL;
}
ccl_device int bsdf_microfacet_ggx_fresnel_setup(MicrofacetBsdf *bsdf)
ccl_device int bsdf_microfacet_ggx_fresnel_setup(MicrofacetBsdf *bsdf, const ShaderData *sd)
{
bsdf->extra->cspec0.x = saturate(bsdf->extra->cspec0.x);
bsdf->extra->cspec0.y = saturate(bsdf->extra->cspec0.y);
bsdf->extra->cspec0.z = saturate(bsdf->extra->cspec0.z);
float F0 = fresnel_dielectric_cos(1.0f, bsdf->ior);
float F = average(interpolate_fresnel_color(sd->I, bsdf->N, bsdf->ior, F0, bsdf->extra->cspec0));
bsdf->sample_weight *= F;
bsdf->alpha_x = saturate(bsdf->alpha_x);
bsdf->alpha_y = bsdf->alpha_x;
@ -302,12 +306,16 @@ ccl_device int bsdf_microfacet_ggx_fresnel_setup(MicrofacetBsdf *bsdf)
return SD_BSDF|SD_BSDF_HAS_EVAL;
}
ccl_device int bsdf_microfacet_ggx_clearcoat_setup(MicrofacetBsdf *bsdf)
ccl_device int bsdf_microfacet_ggx_clearcoat_setup(MicrofacetBsdf *bsdf, const ShaderData *sd)
{
bsdf->extra->cspec0.x = saturate(bsdf->extra->cspec0.x);
bsdf->extra->cspec0.y = saturate(bsdf->extra->cspec0.y);
bsdf->extra->cspec0.z = saturate(bsdf->extra->cspec0.z);
float F0 = fresnel_dielectric_cos(1.0f, bsdf->ior);
float F = average(interpolate_fresnel_color(sd->I, bsdf->N, bsdf->ior, F0, bsdf->extra->cspec0));
bsdf->sample_weight *= 0.25f * bsdf->extra->clearcoat * F;
bsdf->alpha_x = saturate(bsdf->alpha_x);
bsdf->alpha_y = bsdf->alpha_x;
@ -343,12 +351,16 @@ ccl_device int bsdf_microfacet_ggx_aniso_setup(MicrofacetBsdf *bsdf)
return SD_BSDF|SD_BSDF_HAS_EVAL;
}
ccl_device int bsdf_microfacet_ggx_aniso_fresnel_setup(MicrofacetBsdf *bsdf)
ccl_device int bsdf_microfacet_ggx_aniso_fresnel_setup(MicrofacetBsdf *bsdf, const ShaderData *sd)
{
bsdf->extra->cspec0.x = saturate(bsdf->extra->cspec0.x);
bsdf->extra->cspec0.y = saturate(bsdf->extra->cspec0.y);
bsdf->extra->cspec0.z = saturate(bsdf->extra->cspec0.z);
float F0 = fresnel_dielectric_cos(1.0f, bsdf->ior);
float F = average(interpolate_fresnel_color(sd->I, bsdf->N, bsdf->ior, F0, bsdf->extra->cspec0));
bsdf->sample_weight *= F;
bsdf->alpha_x = saturate(bsdf->alpha_x);
bsdf->alpha_y = saturate(bsdf->alpha_y);

18
intern/cycles/kernel/closure/bsdf_microfacet_multi.h
View File

@ -360,13 +360,17 @@ ccl_device int bsdf_microfacet_multi_ggx_aniso_setup(MicrofacetBsdf *bsdf)
return bsdf_microfacet_multi_ggx_common_setup(bsdf);
}
ccl_device int bsdf_microfacet_multi_ggx_aniso_fresnel_setup(MicrofacetBsdf *bsdf)
ccl_device int bsdf_microfacet_multi_ggx_aniso_fresnel_setup(MicrofacetBsdf *bsdf, const ShaderData *sd)
{
if(is_zero(bsdf->T))
bsdf->T = make_float3(1.0f, 0.0f, 0.0f);
bsdf->type = CLOSURE_BSDF_MICROFACET_MULTI_GGX_FRESNEL_ID;
float F0 = fresnel_dielectric_cos(1.0f, bsdf->ior);
float F = average(interpolate_fresnel_color(sd->I, bsdf->N, bsdf->ior, F0, bsdf->extra->cspec0));
bsdf->sample_weight *= F;
return bsdf_microfacet_multi_ggx_common_setup(bsdf);
}
@ -379,12 +383,16 @@ ccl_device int bsdf_microfacet_multi_ggx_setup(MicrofacetBsdf *bsdf)
return bsdf_microfacet_multi_ggx_common_setup(bsdf);
}
ccl_device int bsdf_microfacet_multi_ggx_fresnel_setup(MicrofacetBsdf *bsdf)
ccl_device int bsdf_microfacet_multi_ggx_fresnel_setup(MicrofacetBsdf *bsdf, const ShaderData *sd)
{
bsdf->alpha_y = bsdf->alpha_x;
bsdf->type = CLOSURE_BSDF_MICROFACET_MULTI_GGX_FRESNEL_ID;
float F0 = fresnel_dielectric_cos(1.0f, bsdf->ior);
float F = average(interpolate_fresnel_color(sd->I, bsdf->N, bsdf->ior, F0, bsdf->extra->cspec0));
bsdf->sample_weight *= F;
return bsdf_microfacet_multi_ggx_common_setup(bsdf);
}
@ -489,7 +497,7 @@ ccl_device int bsdf_microfacet_multi_ggx_glass_setup(MicrofacetBsdf *bsdf)
return SD_BSDF|SD_BSDF_HAS_EVAL|SD_BSDF_NEEDS_LCG;
}
ccl_device int bsdf_microfacet_multi_ggx_glass_fresnel_setup(MicrofacetBsdf *bsdf)
ccl_device int bsdf_microfacet_multi_ggx_glass_fresnel_setup(MicrofacetBsdf *bsdf, const ShaderData *sd)
{
bsdf->alpha_x = clamp(bsdf->alpha_x, 1e-4f, 1.0f);
bsdf->alpha_y = bsdf->alpha_x;
@ -503,6 +511,10 @@ ccl_device int bsdf_microfacet_multi_ggx_glass_fresnel_setup(MicrofacetBsdf *bsd
bsdf->type = CLOSURE_BSDF_MICROFACET_MULTI_GGX_GLASS_FRESNEL_ID;
float F0 = fresnel_dielectric_cos(1.0f, bsdf->ior);
float F = average(interpolate_fresnel_color(sd->I, bsdf->N, bsdf->ior, F0, bsdf->extra->cspec0));
bsdf->sample_weight *= F;
return SD_BSDF|SD_BSDF_HAS_EVAL|SD_BSDF_NEEDS_LCG;
}

12
intern/cycles/kernel/osl/osl_closures.cpp
View File

@ -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;
}
};

10
intern/cycles/kernel/svm/svm_closure.h
View File

@ -292,9 +292,9 @@ ccl_device void svm_node_closure_bsdf(KernelGlobals *kg, ShaderData *sd, float *
/* setup bsdf */
if(distribution == CLOSURE_BSDF_MICROFACET_GGX_GLASS_ID || roughness <= 0.075f) /* use single-scatter GGX */
sd->flag |= bsdf_microfacet_ggx_aniso_fresnel_setup(bsdf);
sd->flag |= bsdf_microfacet_ggx_aniso_fresnel_setup(bsdf, sd);
else /* use multi-scatter GGX */
sd->flag |= bsdf_microfacet_multi_ggx_aniso_fresnel_setup(bsdf);
sd->flag |= bsdf_microfacet_multi_ggx_aniso_fresnel_setup(bsdf, sd);
}
}
#ifdef __CAUSTICS_TRICKS__
@ -332,7 +332,7 @@ ccl_device void svm_node_closure_bsdf(KernelGlobals *kg, ShaderData *sd, float *
bsdf->extra->cspec0 = cspec0;
/* setup bsdf */
sd->flag |= bsdf_microfacet_ggx_fresnel_setup(bsdf);
sd->flag |= bsdf_microfacet_ggx_fresnel_setup(bsdf, sd);
}
}
@ -377,7 +377,7 @@ ccl_device void svm_node_closure_bsdf(KernelGlobals *kg, ShaderData *sd, float *
bsdf->extra->cspec0 = cspec0;
/* setup bsdf */
sd->flag |= bsdf_microfacet_multi_ggx_glass_fresnel_setup(bsdf);
sd->flag |= bsdf_microfacet_multi_ggx_glass_fresnel_setup(bsdf, sd);
}
}
}
@ -405,7 +405,7 @@ ccl_device void svm_node_closure_bsdf(KernelGlobals *kg, ShaderData *sd, float *
bsdf->extra->clearcoat = clearcoat;
/* setup bsdf */
sd->flag |= bsdf_microfacet_ggx_clearcoat_setup(bsdf);
sd->flag |= bsdf_microfacet_ggx_clearcoat_setup(bsdf, sd);
}
}
#ifdef __CAUSTICS_TRICKS__