Fix T51849: change Cycles clearcoat gloss to roughness.

This is compatible with UE4 and more consistent with specular and transmission
roughness, even if it deviates from the original Disney BRDF.

4 files changed, 12 insertions, 12 deletions

diff --git a/intern/cycles/kernel/osl/osl_closures.cpp b/intern/cycles/kernel/osl/osl_closures.cpp
index 5b66793a05d..f76fc0d6fea 100644
--- a/intern/cycles/kernel/osl/osl_closures.cpp
+++ b/intern/cycles/kernel/osl/osl_closures.cpp
@@ -191,7 +191,7 @@ BSDF_CLOSURE_CLASS_END(PrincipledSheen, principled_sheen)
 class PrincipledClearcoatClosure : public CBSDFClosure {
 public:
 	MicrofacetBsdf params;
-	float clearcoat, clearcoat_gloss;
+	float clearcoat, clearcoat_roughness;
 
 	MicrofacetBsdf *alloc(ShaderData *sd, int path_flag, float3 weight)
 	{
@@ -202,8 +202,8 @@ public:
 
 			bsdf->ior = 1.5f;
 
-			bsdf->alpha_x = 0.1f * (1.0f - clearcoat_gloss) + 0.001f * clearcoat_gloss;
-			bsdf->alpha_y = 0.1f * (1.0f - clearcoat_gloss) + 0.001f * clearcoat_gloss;
+			bsdf->alpha_x = clearcoat_roughness;
+			bsdf->alpha_y = clearcoat_roughness;
 
 			bsdf->extra->cspec0 = make_float3(0.04f, 0.04f, 0.04f);
 			bsdf->extra->clearcoat = clearcoat;
@@ -226,7 +226,7 @@ ClosureParam *closure_bsdf_principled_clearcoat_params()
 	static ClosureParam params[] = {
 		CLOSURE_FLOAT3_PARAM(PrincipledClearcoatClosure, params.N),
 		CLOSURE_FLOAT_PARAM(PrincipledClearcoatClosure, clearcoat),
-		CLOSURE_FLOAT_PARAM(PrincipledClearcoatClosure, clearcoat_gloss),
+		CLOSURE_FLOAT_PARAM(PrincipledClearcoatClosure, clearcoat_roughness),
 		CLOSURE_STRING_KEYPARAM(PrincipledClearcoatClosure, label, "label"),
 		CLOSURE_FINISH_PARAM(PrincipledClearcoatClosure)
 	};
diff --git a/intern/cycles/kernel/shaders/node_principled_bsdf.osl b/intern/cycles/kernel/shaders/node_principled_bsdf.osl
index 9d85d56ba78..2bb981c3918 100644
--- a/intern/cycles/kernel/shaders/node_principled_bsdf.osl
+++ b/intern/cycles/kernel/shaders/node_principled_bsdf.osl
@@ -32,7 +32,7 @@ shader node_principled_bsdf(
 	float Sheen = 0.0,
 	float SheenTint = 0.5,
 	float Clearcoat = 0.0,
-	float ClearcoatGloss = 1.0,
+	float ClearcoatRoughness = 0.03,
 	float IOR = 1.45,
 	float Transmission = 0.0,
 	float TransmissionRoughness = 0.0,
@@ -114,7 +114,7 @@ shader node_principled_bsdf(
 	}
 
 	if (Clearcoat > 1e-5) {
-		BSDF = BSDF + principled_clearcoat(ClearcoatNormal, Clearcoat, ClearcoatGloss);
+		BSDF = BSDF + principled_clearcoat(ClearcoatNormal, Clearcoat, ClearcoatRoughness * ClearcoatRoughness);
 	}
 }
 
diff --git a/intern/cycles/kernel/shaders/stdosl.h b/intern/cycles/kernel/shaders/stdosl.h
index 289d1091b0a..c91d2918687 100644
--- a/intern/cycles/kernel/shaders/stdosl.h
+++ b/intern/cycles/kernel/shaders/stdosl.h
@@ -546,7 +546,7 @@ closure color holdout() BUILTIN;
 closure color ambient_occlusion() BUILTIN;
 closure color principled_diffuse(normal N, float roughness) BUILTIN;
 closure color principled_sheen(normal N) BUILTIN;
-closure color principled_clearcoat(normal N, float clearcoat, float clearcoat_gloss) BUILTIN;
+closure color principled_clearcoat(normal N, float clearcoat, float clearcoat_roughness) BUILTIN;
 
 // BSSRDF
 closure color bssrdf_cubic(normal N, vector radius, float texture_blur, float sharpness) BUILTIN;
diff --git a/intern/cycles/kernel/svm/svm_closure.h b/intern/cycles/kernel/svm/svm_closure.h
index f3bbd7a7dac..c05da61ba5a 100644
--- a/intern/cycles/kernel/svm/svm_closure.h
+++ b/intern/cycles/kernel/svm/svm_closure.h
@@ -79,13 +79,13 @@ ccl_device void svm_node_closure_bsdf(KernelGlobals *kg, ShaderData *sd, float *
 #ifdef __PRINCIPLED__
 		case CLOSURE_BSDF_PRINCIPLED_ID: {
 			uint specular_offset, roughness_offset, specular_tint_offset, anisotropic_offset, sheen_offset,
-				sheen_tint_offset, clearcoat_offset, clearcoat_gloss_offset, eta_offset, transmission_offset,
+				sheen_tint_offset, clearcoat_offset, clearcoat_roughness_offset, eta_offset, transmission_offset,
 				anisotropic_rotation_offset, transmission_roughness_offset;
 			uint4 data_node2 = read_node(kg, offset);
 
 			float3 T = stack_load_float3(stack, data_node.y);
 			decode_node_uchar4(data_node.z, &specular_offset, &roughness_offset, &specular_tint_offset, &anisotropic_offset);
-			decode_node_uchar4(data_node.w, &sheen_offset, &sheen_tint_offset, &clearcoat_offset, &clearcoat_gloss_offset);
+			decode_node_uchar4(data_node.w, &sheen_offset, &sheen_tint_offset, &clearcoat_offset, &clearcoat_roughness_offset);
 			decode_node_uchar4(data_node2.x, &eta_offset, &transmission_offset, &anisotropic_rotation_offset, &transmission_roughness_offset);
 
 			// get Disney principled parameters
@@ -98,7 +98,7 @@ ccl_device void svm_node_closure_bsdf(KernelGlobals *kg, ShaderData *sd, float *
 			float sheen = stack_load_float(stack, sheen_offset);
 			float sheen_tint = stack_load_float(stack, sheen_tint_offset);
 			float clearcoat = stack_load_float(stack, clearcoat_offset);
-			float clearcoat_gloss = stack_load_float(stack, clearcoat_gloss_offset);
+			float clearcoat_roughness = stack_load_float(stack, clearcoat_roughness_offset);
 			float transmission = stack_load_float(stack, transmission_offset);
 			float anisotropic_rotation = stack_load_float(stack, anisotropic_rotation_offset);
 			float transmission_roughness = stack_load_float(stack, transmission_roughness_offset);
@@ -398,8 +398,8 @@ ccl_device void svm_node_closure_bsdf(KernelGlobals *kg, ShaderData *sd, float *
 						bsdf->ior = 1.5f;
 						bsdf->extra = extra;
 
-						bsdf->alpha_x = 0.1f * (1.0f - clearcoat_gloss) + 0.001f * clearcoat_gloss;
-						bsdf->alpha_y = 0.1f * (1.0f - clearcoat_gloss) + 0.001f * clearcoat_gloss;
+						bsdf->alpha_x = clearcoat_roughness * clearcoat_roughness;
+						bsdf->alpha_y = clearcoat_roughness * clearcoat_roughness;
 
 						bsdf->extra->cspec0 = make_float3(0.04f, 0.04f, 0.04f);
 						bsdf->extra->clearcoat = clearcoat;