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.

2 files changed, 3 insertions, 3 deletions

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;