Fix Cycles viewport render not updating when tweaking displacement shader.

This was disabled to avoid updating the geometry every time when the
material includes displacement, because there was no way to distinguish
between surface shader and displacement updates.

As a solution, we now compute an MD5 hash of the nodes linked to the
displacement socket, and only update the mesh if that changes.

Differential Revision: https://developer.blender.org/D3018

intern/cycles/blender/blender_mesh.cpp

@@ -1123,7 +1123,7 @@ Mesh *BlenderSync::sync_mesh(BL::Object& b_ob,
 			bool attribute_recalc = false;
 
 			foreach(Shader *shader, mesh->used_shaders)
-				if(shader->need_update_attributes)
+				if(shader->need_update_mesh)
 					attribute_recalc = true;
 
 			if(!attribute_recalc)

intern/cycles/graph/node.cpp

@@ -18,6 +18,7 @@
 #include "graph/node_type.h"
 
 #include "util/util_foreach.h"
+#include "util/util_md5.h"
 #include "util/util_param.h"
 #include "util/util_transform.h"
 
@@ -403,5 +404,24 @@ bool Node::equals(const Node& other) const
 	return true;
 }
 
+/* Hash */
+
+void Node::hash(MD5Hash& md5)
+{
+	md5.append(type->name.string());
+
+	foreach(const SocketType& socket, type->inputs) {
+		md5.append(socket.name.string());
+
+		if(socket.is_array()) {
+			const array<bool>* a = (const array<bool>*)(((char*)this) + socket.struct_offset);
+			md5.append((uint8_t*)a->data(), socket.size() * a->size());
+		}
+		else {
+			md5.append(((uint8_t*)this) + socket.struct_offset, socket.size());
+		}
+	}
+}
+
 CCL_NAMESPACE_END
 

intern/cycles/graph/node.h

@@ -24,6 +24,7 @@
 
 CCL_NAMESPACE_BEGIN
 
+class MD5Hash;
 struct Node;
 struct NodeType;
 struct Transform;
@@ -88,6 +89,9 @@ struct Node
 	/* equals */
 	bool equals(const Node& other) const;
 
+	/* compute hash of node and its socket values */
+	void hash(MD5Hash& md5);
+
 	ustring name;
 	const NodeType *type;
 };

intern/cycles/render/film.cpp

@@ -496,7 +496,7 @@ void Film::tag_passes_update(Scene *scene, const array<Pass>& passes_)
 		scene->mesh_manager->tag_update(scene);
 
 		foreach(Shader *shader, scene->shaders)
-			shader->need_update_attributes = true;
+			shader->need_update_mesh = true;
 	}
 	else if(Pass::contains(passes, PASS_MOTION) != Pass::contains(passes_, PASS_MOTION))
 		scene->mesh_manager->tag_update(scene);

intern/cycles/render/graph.cpp

@@ -23,8 +23,9 @@
 
 #include "util/util_algorithm.h"
 #include "util/util_foreach.h"
-#include "util/util_queue.h"
 #include "util/util_logging.h"
+#include "util/util_md5.h"
+#include "util/util_queue.h"
 
 CCL_NAMESPACE_BEGIN
 
@@ -683,6 +684,32 @@ void ShaderGraph::break_cycles(ShaderNode *node, vector<bool>& visited, vector<b
 	on_stack[node->id] = false;
 }
 
+void ShaderGraph::compute_displacement_hash()
+{
+	/* Compute hash of all nodes linked to displacement, to detect if we need
+	 * to recompute displacement when shader nodes change. */
+	ShaderInput *displacement_in = output()->input("Displacement");
+
+	if(!displacement_in->link) {
+		displacement_hash = "";
+		return;
+	}
+
+	ShaderNodeSet nodes_displace;
+	find_dependencies(nodes_displace, displacement_in);
+
+	MD5Hash md5;
+	foreach(ShaderNode *node, nodes_displace) {
+		node->hash(md5);
+		foreach(ShaderInput *input, node->inputs) {
+			int link_id = (input->link) ? input->link->parent->id : 0;
+			md5.append((uint8_t*)&link_id, sizeof(link_id));
+		}
+	}
+
+	displacement_hash = md5.get_hex();
+}
+
 void ShaderGraph::clean(Scene *scene)
 {
 	/* Graph simplification */

intern/cycles/render/graph.h

@@ -42,6 +42,7 @@ class SVMCompiler;
 class OSLCompiler;
 class OutputNode;
 class ConstantFolder;
+class MD5Hash;
 
 /* Bump
  *
@@ -243,6 +244,7 @@ public:
 	size_t num_node_ids;
 	bool finalized;
 	bool simplified;
+	string displacement_hash;
 
 	ShaderGraph();
 	~ShaderGraph();
@@ -256,6 +258,7 @@ public:
 	void relink(ShaderNode *node, ShaderOutput *from, ShaderOutput *to);
 
 	void remove_proxy_nodes();
+	void compute_displacement_hash();
 	void simplify(Scene *scene);
 	void finalize(Scene *scene,
 	              bool do_bump = false,

intern/cycles/render/mesh.cpp

@@ -1964,7 +1964,7 @@ void MeshManager::device_update(Device *device, DeviceScene *dscene, Scene *scen
 	/* Update normals. */
 	foreach(Mesh *mesh, scene->meshes) {
 		foreach(Shader *shader, mesh->used_shaders) {
-			if(shader->need_update_attributes)
+			if(shader->need_update_mesh)
 				mesh->need_update = true;
 		}
 
@@ -2104,7 +2104,7 @@ void MeshManager::device_update(Device *device, DeviceScene *dscene, Scene *scen
 	        << summary.full_report();
 
 	foreach(Shader *shader, scene->shaders) {
-		shader->need_update_attributes = false;
+		shader->need_update_mesh = false;
 	}
 
 	Scene::MotionType need_motion = scene->need_motion();

intern/cycles/render/shader.cpp

@@ -200,7 +200,7 @@ Shader::Shader()
 	used = false;
 
 	need_update = true;
-	need_update_attributes = true;
+	need_update_mesh = true;
 }
 
 Shader::~Shader()
@@ -235,9 +235,24 @@ void Shader::set_graph(ShaderGraph *graph_)
 	/* do this here already so that we can detect if mesh or object attributes
 	 * are needed, since the node attribute callbacks check if their sockets
 	 * are connected but proxy nodes should not count */
-	if(graph_)
+	if(graph_) {
 		graph_->remove_proxy_nodes();
 
+		if(displacement_method != DISPLACE_BUMP) {
+			graph_->compute_displacement_hash();
+		}
+	}
+
+	/* update geometry if displacement changed */
+	if(displacement_method != DISPLACE_BUMP) {
+		const char *old_hash = (graph)? graph->displacement_hash.c_str() : "";
+		const char *new_hash = (graph_)? graph_->displacement_hash.c_str() : "";
+
+		if(strcmp(old_hash, new_hash) != 0) {
+			need_update_mesh = true;
+		}
+	}
+
 	/* assign graph */
 	delete graph;
 	graph = graph_;
@@ -294,9 +309,9 @@ void Shader::tag_update(Scene *scene)
 	}
 	
 	/* compare if the attributes changed, mesh manager will check
-	 * need_update_attributes, update the relevant meshes and clear it. */
+	 * need_update_mesh, update the relevant meshes and clear it. */
 	if(attributes.modified(prev_attributes)) {
-		need_update_attributes = true;
+		need_update_mesh = true;
 		scene->mesh_manager->need_update = true;
 	}
 

intern/cycles/render/shader.h

@@ -98,7 +98,7 @@ public:
 
 	/* synchronization */
 	bool need_update;
-	bool need_update_attributes;
+	bool need_update_mesh;
 
 	/* If the shader has only volume components, the surface is assumed to
 	 * be transparent.

intern/cycles/util/util_md5.cpp

@@ -310,6 +310,13 @@ void MD5Hash::append(const uint8_t *data, int nbytes)
 		memcpy(buf, p, left);
 }
 
+void MD5Hash::append(const string& str)
+{
+	if(str.size()) {
+		append((const uint8_t*)str.c_str(), str.size());
+	}
+}
+
 bool MD5Hash::append_file(const string& filepath)
 {
 	FILE *f = path_fopen(filepath, "rb");

intern/cycles/util/util_md5.h

@@ -41,6 +41,7 @@ public:
 	~MD5Hash();
 
 	void append(const uint8_t *data, int size);
+	void append(const string& str);
 	bool append_file(const string& filepath);
 	string get_hex();