Cycles: Consider GGX/Beckmann/Ashikhmin of 0 roughness a singular ray

This matches behavior of Multiscatter GGX and could become handy later on
when/if we decide it would be beneficial to replace on closure with another.

Reviewers: lukasstockner97, brecht

Reviewed By: brecht

Differential Revision: https://developer.blender.org/D2413

2 files changed, 17 insertions, 3 deletions

diff --git a/intern/cycles/kernel/closure/bsdf_ashikhmin_shirley.h b/intern/cycles/kernel/closure/bsdf_ashikhmin_shirley.h
index 1cd8246aa71..b6c896c754b 100644
--- a/intern/cycles/kernel/closure/bsdf_ashikhmin_shirley.h
+++ b/intern/cycles/kernel/closure/bsdf_ashikhmin_shirley.h
@@ -143,6 +143,7 @@ ccl_device int bsdf_ashikhmin_shirley_sample(const ShaderClosure *sc, float3 Ng,
 {
 	const MicrofacetBsdf *bsdf = (const MicrofacetBsdf*)sc;
 	float3 N = bsdf->N;
+	int label = LABEL_REFLECT | LABEL_GLOSSY;
 
 	float NdotI = dot(N, I);
 	if(NdotI > 0.0f) {
@@ -211,6 +212,7 @@ ccl_device int bsdf_ashikhmin_shirley_sample(const ShaderClosure *sc, float3 Ng,
 			/* Some high number for MIS. */
 			*pdf = 1e6f;
 			*eval = make_float3(1e6f, 1e6f, 1e6f);
+			label = LABEL_REFLECT | LABEL_SINGULAR;
 		}
 		else {
 			/* leave the rest to eval_reflect */
@@ -224,7 +226,7 @@ ccl_device int bsdf_ashikhmin_shirley_sample(const ShaderClosure *sc, float3 Ng,
 #endif
 	}
 
-	return LABEL_REFLECT|LABEL_GLOSSY;
+	return label;
 }
 
 
diff --git a/intern/cycles/kernel/closure/bsdf_microfacet.h b/intern/cycles/kernel/closure/bsdf_microfacet.h
index 0a8d14a00c2..72fffe6ff69 100644
--- a/intern/cycles/kernel/closure/bsdf_microfacet.h
+++ b/intern/cycles/kernel/closure/bsdf_microfacet.h
@@ -452,6 +452,7 @@ ccl_device int bsdf_microfacet_ggx_sample(KernelGlobals *kg, const ShaderClosure
 	float alpha_y = bsdf->alpha_y;
 	bool m_refractive = bsdf->type == CLOSURE_BSDF_MICROFACET_GGX_REFRACTION_ID;
 	float3 N = bsdf->N;
+	int label;
 
 	float cosNO = dot(N, I);
 	if(cosNO > 0) {
@@ -477,6 +478,7 @@ ccl_device int bsdf_microfacet_ggx_sample(KernelGlobals *kg, const ShaderClosure
 		/* reflection or refraction? */
 		if(!m_refractive) {
 			float cosMO = dot(m, I);
+			label = LABEL_REFLECT | LABEL_GLOSSY;
 
 			if(cosMO > 0) {
 				/* eq. 39 - compute actual reflected direction */
@@ -487,6 +489,7 @@ ccl_device int bsdf_microfacet_ggx_sample(KernelGlobals *kg, const ShaderClosure
 						/* some high number for MIS */
 						*pdf = 1e6f;
 						*eval = make_float3(1e6f, 1e6f, 1e6f);
+						label = LABEL_REFLECT | LABEL_SINGULAR;
 					}
 					else {
 						/* microfacet normal is visible to this ray */
@@ -549,6 +552,8 @@ ccl_device int bsdf_microfacet_ggx_sample(KernelGlobals *kg, const ShaderClosure
 			}
 		}
 		else {
+			label = LABEL_TRANSMIT | LABEL_GLOSSY;
+
 			/* CAUTION: the i and o variables are inverted relative to the paper
 			 * eq. 39 - compute actual refractive direction */
 			float3 R, T;
@@ -576,6 +581,7 @@ ccl_device int bsdf_microfacet_ggx_sample(KernelGlobals *kg, const ShaderClosure
 					/* some high number for MIS */
 					*pdf = 1e6f;
 					*eval = make_float3(1e6f, 1e6f, 1e6f);
+					label = LABEL_TRANSMIT | LABEL_SINGULAR;
 				}
 				else {
 					/* eq. 33 */
@@ -607,7 +613,7 @@ ccl_device int bsdf_microfacet_ggx_sample(KernelGlobals *kg, const ShaderClosure
 			}
 		}
 	}
-	return (m_refractive) ? LABEL_TRANSMIT|LABEL_GLOSSY : LABEL_REFLECT|LABEL_GLOSSY;
+	return label;
 }
 
 /* Beckmann microfacet with Smith shadow-masking from:
@@ -815,6 +821,7 @@ ccl_device int bsdf_microfacet_beckmann_sample(KernelGlobals *kg, const ShaderCl
 	float alpha_y = bsdf->alpha_y;
 	bool m_refractive = bsdf->type == CLOSURE_BSDF_MICROFACET_BECKMANN_REFRACTION_ID;
 	float3 N = bsdf->N;
+	int label;
 
 	float cosNO = dot(N, I);
 	if(cosNO > 0) {
@@ -839,6 +846,7 @@ ccl_device int bsdf_microfacet_beckmann_sample(KernelGlobals *kg, const ShaderCl
 
 		/* reflection or refraction? */
 		if(!m_refractive) {
+			label = LABEL_REFLECT | LABEL_GLOSSY;
 			float cosMO = dot(m, I);
 
 			if(cosMO > 0) {
@@ -850,6 +858,7 @@ ccl_device int bsdf_microfacet_beckmann_sample(KernelGlobals *kg, const ShaderCl
 						/* some high number for MIS */
 						*pdf = 1e6f;
 						*eval = make_float3(1e6f, 1e6f, 1e6f);
+						label = LABEL_REFLECT | LABEL_SINGULAR;
 					}
 					else {
 						/* microfacet normal is visible to this ray
@@ -904,6 +913,8 @@ ccl_device int bsdf_microfacet_beckmann_sample(KernelGlobals *kg, const ShaderCl
 			}
 		}
 		else {
+			label = LABEL_TRANSMIT | LABEL_GLOSSY;
+
 			/* CAUTION: the i and o variables are inverted relative to the paper
 			 * eq. 39 - compute actual refractive direction */
 			float3 R, T;
@@ -931,6 +942,7 @@ ccl_device int bsdf_microfacet_beckmann_sample(KernelGlobals *kg, const ShaderCl
 					/* some high number for MIS */
 					*pdf = 1e6f;
 					*eval = make_float3(1e6f, 1e6f, 1e6f);
+					label = LABEL_TRANSMIT | LABEL_SINGULAR;
 				}
 				else {
 					/* eq. 33 */
@@ -963,7 +975,7 @@ ccl_device int bsdf_microfacet_beckmann_sample(KernelGlobals *kg, const ShaderCl
 			}
 		}
 	}
-	return (m_refractive) ? LABEL_TRANSMIT|LABEL_GLOSSY : LABEL_REFLECT|LABEL_GLOSSY;
+	return label;
 }
 
 CCL_NAMESPACE_END