Cycles: Enable SSS from Principled BSDF only when actually in use

This gives speed up for the split kernel in scenes using the principled BSDF
but without subsurface scattering.

2 files changed, 7 insertions, 1 deletions

diff --git a/intern/cycles/render/nodes.cpp b/intern/cycles/render/nodes.cpp
index 166156f7ac3..86e25df1da3 100644
--- a/intern/cycles/render/nodes.cpp
+++ b/intern/cycles/render/nodes.cpp
@@ -2337,6 +2337,12 @@ PrincipledBsdfNode::PrincipledBsdfNode()
 	distribution_orig = NBUILTIN_CLOSURES;
 }
 
+bool PrincipledBsdfNode::has_surface_bssrdf()
+{
+	ShaderInput *subsurface_in = input("Subsurface");
+	return (subsurface_in->link != NULL || subsurface > CLOSURE_WEIGHT_CUTOFF);
+}
+
 void PrincipledBsdfNode::attributes(Shader *shader, AttributeRequestSet *attributes)
 {
 	if(shader->has_surface) {
diff --git a/intern/cycles/render/nodes.h b/intern/cycles/render/nodes.h
index c6ab47fcc84..c0271a3c8eb 100644
--- a/intern/cycles/render/nodes.h
+++ b/intern/cycles/render/nodes.h
@@ -374,7 +374,7 @@ public:
 	SHADER_NODE_CLASS(PrincipledBsdfNode)
 
 	bool has_spatial_varying() { return true; }
-	bool has_surface_bssrdf() { return true; }
+	bool has_surface_bssrdf();
 	bool has_bssrdf_bump();
 	void compile(SVMCompiler& compiler, ShaderInput *metallic, ShaderInput *subsurface, ShaderInput *subsurface_radius,
 		ShaderInput *specular, ShaderInput *roughness, ShaderInput *specular_tint, ShaderInput *anisotropic,