Cycles: Optimize shaders earlier to skip unneccessary attributes for noninteractive rendering

Before, Cycles would first sync the shader exactly as shown in the UI, then determine and sync the used attributes and later optimize the shader.
Therefore, even completely unconnected nodes would cause unneccessary attributes to be synced.

The reason for this is to avoid frequent resyncs when editing shaders interactively, but it can still be avoided for noninteractive renders - which is what this commit does.

Reviewed by: sergey

Differential Revision: https://developer.blender.org/D2285

intern/cycles/blender/blender_shader.cpp

@@ -28,6 +28,7 @@
 
 #include "util_debug.h"
 #include "util_string.h"
+#include "util_task.h"
 
 CCL_NAMESPACE_BEGIN
 
@@ -1164,6 +1165,8 @@ void BlenderSync::sync_materials(bool update_all)
 	/* material loop */
 	BL::BlendData::materials_iterator b_mat;
 
+	TaskPool pool;
+
 	for(b_data.materials.begin(b_mat); b_mat != b_data.materials.end(); ++b_mat) {
 		Shader *shader;
 
@@ -1199,9 +1202,22 @@ void BlenderSync::sync_materials(bool update_all)
 			shader->displacement_method = (experimental) ? get_displacement_method(cmat) : DISPLACE_BUMP;
 
 			shader->set_graph(graph);
+
+			/* By simplifying the shader graph as soon as possible, some redundant shader nodes
+			 * might be removed which prevents loading unneccessary attributes later.
+			 *
+			 * However, since graph simplification also accounts for e.g. mix weight, this would
+			 * cause frequent expensive resyncs in interactive sessions, so for those sessions
+			 * optimization is only performed right before compiling. */
+			if(!preview) {
+				pool.push(function_bind(&ShaderGraph::simplify, shader->graph, scene));
+			}
+
 			shader->tag_update(scene);
 		}
 	}
+
+	pool.wait_work();
 }
 
 /* Sync World */

intern/cycles/render/graph.cpp

@@ -17,6 +17,7 @@
 #include "attribute.h"
 #include "graph.h"
 #include "nodes.h"
+#include "scene.h"
 #include "shader.h"
 #include "constant_fold.h"
 
@@ -195,6 +196,7 @@ bool ShaderNode::equals(const ShaderNode& other)
 ShaderGraph::ShaderGraph()
 {
 	finalized = false;
+	simplified = false;
 	num_node_ids = 0;
 	add(new OutputNode());
 }
@@ -207,6 +209,8 @@ ShaderGraph::~ShaderGraph()
 ShaderNode *ShaderGraph::add(ShaderNode *node)
 {
 	assert(!finalized);
+	simplified = false;
+
 	node->id = num_node_ids++;
 	nodes.push_back(node);
 	return node;
@@ -241,6 +245,7 @@ void ShaderGraph::connect(ShaderOutput *from, ShaderInput *to)
 {
 	assert(!finalized);
 	assert(from && to);
+	simplified = false;
 
 	if(to->link) {
 		fprintf(stderr, "Cycles shader graph connect: input already connected.\n");
@@ -273,6 +278,7 @@ void ShaderGraph::connect(ShaderOutput *from, ShaderInput *to)
 void ShaderGraph::disconnect(ShaderOutput *from)
 {
 	assert(!finalized);
+	simplified = false;
 
 	foreach(ShaderInput *sock, from->links) {
 		sock->link = NULL;
@@ -285,6 +291,7 @@ void ShaderGraph::disconnect(ShaderInput *to)
 {
 	assert(!finalized);
 	assert(to->link);
+	simplified = false;
 
 	ShaderOutput *from = to->link;
 
@@ -294,6 +301,8 @@ void ShaderGraph::disconnect(ShaderInput *to)
 
 void ShaderGraph::relink(ShaderNode *node, ShaderOutput *from, ShaderOutput *to)
 {
+	simplified = false;
+
 	/* Copy because disconnect modifies this list */
 	vector<ShaderInput*> outputs = from->links;
 
@@ -310,9 +319,19 @@ void ShaderGraph::relink(ShaderNode *node, ShaderOutput *from, ShaderOutput *to)
 	}
 }
 
+void ShaderGraph::simplify(Scene *scene)
+{
+	if(!simplified) {
+		default_inputs(scene->shader_manager->use_osl());
+		clean(scene);
+		refine_bump_nodes();
+
+		simplified = true;
+	}
+}
+
 void ShaderGraph::finalize(Scene *scene,
                            bool do_bump,
-                           bool do_osl,
                            bool do_simplify,
                            bool bump_in_object_space)
 {
@@ -322,9 +341,7 @@ void ShaderGraph::finalize(Scene *scene,
 	 * modified afterwards. */
 
 	if(!finalized) {
-		default_inputs(do_osl);
-		clean(scene);
-		refine_bump_nodes();
+		simplify(scene);
 
 		if(do_bump)
 			bump_from_displacement(bump_in_object_space);

intern/cycles/render/graph.h

@@ -240,6 +240,7 @@ public:
 	list<ShaderNode*> nodes;
 	size_t num_node_ids;
 	bool finalized;
+	bool simplified;
 
 	ShaderGraph();
 	~ShaderGraph();
@@ -255,9 +256,9 @@ public:
 	void relink(ShaderNode *node, ShaderOutput *from, ShaderOutput *to);
 
 	void remove_proxy_nodes();
+	void simplify(Scene *scene);
 	void finalize(Scene *scene,
 	              bool do_bump = false,
-	              bool do_osl = false,
 	              bool do_simplify = false,
 	              bool bump_in_object_space = false);
 

intern/cycles/render/osl.cpp

@@ -1096,11 +1096,9 @@ void OSLCompiler::compile(Scene *scene, OSLGlobals *og, Shader *shader)
 		/* finalize */
 		shader->graph->finalize(scene,
 		                        false,
-		                        true,
 		                        shader->has_integrator_dependency);
 		if(shader->graph_bump) {
 			shader->graph_bump->finalize(scene,
-			                             true,
 			                             true,
 			                             shader->has_integrator_dependency,
 			                             shader->displacement_method == DISPLACE_BOTH);

intern/cycles/render/svm.cpp

@@ -812,7 +812,6 @@ void SVMCompiler::compile(Scene *scene,
 	{
 		scoped_timer timer((summary != NULL)? &summary->time_finalize: NULL);
 		shader->graph->finalize(scene,
-		                        false,
 		                        false,
 		                        shader->has_integrator_dependency);
 	}
@@ -821,7 +820,6 @@ void SVMCompiler::compile(Scene *scene,
 		scoped_timer timer((summary != NULL)? &summary->time_finalize_bump: NULL);
 		shader->graph_bump->finalize(scene,
 		                             true,
-		                             false,
 		                             shader->has_integrator_dependency,
 		                             shader->displacement_method == DISPLACE_BOTH);
 	}