Cycles: Remove Emission shaders from the graph if color or strength is 0.

intern/cycles/render/graph.cpp

@@ -404,6 +404,21 @@ void ShaderGraph::remove_unneeded_nodes()
 				}
 			}
 		}
+		else if(node->special_type == SHADER_SPECIAL_TYPE_EMISSION) {
+			EmissionNode *em = static_cast<EmissionNode*>(node);
+
+			if(em->outputs[0]->links.size()) {
+				/* Black color or zero strength, remove node */
+				if((!em->inputs[0]->link && em->inputs[0]->value == make_float3(0.0f, 0.0f, 0.0f)) ||
+				   (!em->inputs[1]->link && em->inputs[1]->value.x == 0.0f)) {
+					vector<ShaderInput*> inputs = em->outputs[0]->links;
+
+					relink(em->inputs, inputs, NULL);
+					removed[em->id] = true;
+					any_node_removed = true;
+				}
+			}
+		}
 		else if(node->special_type == SHADER_SPECIAL_TYPE_MIX_CLOSURE) {
 			MixClosureNode *mix = static_cast<MixClosureNode*>(node);
 

intern/cycles/render/graph.h

@@ -83,6 +83,7 @@ enum ShaderNodeSpecialType {
 	SHADER_SPECIAL_TYPE_BACKGROUND,
 	SHADER_SPECIAL_TYPE_IMAGE_SLOT,
 	SHADER_SPECIAL_TYPE_CLOSURE,
+	SHADER_SPECIAL_TYPE_EMISSION,
 };
 
 /* Enum

intern/cycles/render/nodes.cpp

@@ -1923,6 +1923,8 @@ bool SubsurfaceScatteringNode::has_bssrdf_bump()
 EmissionNode::EmissionNode()
 : ShaderNode("emission")
 {
+	special_type = SHADER_SPECIAL_TYPE_EMISSION;
+
 	add_input("Color", SHADER_SOCKET_COLOR, make_float3(0.8f, 0.8f, 0.8f));
 	add_input("Strength", SHADER_SOCKET_FLOAT, 10.0f);
 	add_input("SurfaceMixWeight", SHADER_SOCKET_FLOAT, 0.0f, ShaderInput::USE_SVM);