Cycles volume: detect homogeneous volume automatically in common cases.

In practice this means that if you don't connect a texture to your volume nodes
it will figure that out and render the node faster, rather than you having to
specify it manually.

Main weakness is custom OSL nodes where we have to assume it is heterogeneous
because we don't know what kind of data the node accesses.

6 files changed, 44 insertions, 10 deletions

diff --git a/intern/cycles/render/graph.h b/intern/cycles/render/graph.h
index f31e2103229..263ce59156a 100644
--- a/intern/cycles/render/graph.h
+++ b/intern/cycles/render/graph.h
@@ -193,6 +193,7 @@ public:
 	virtual bool has_surface_bssrdf() { return false; }
 	virtual bool has_converter_blackbody() { return false; }
 	virtual bool has_bssrdf_bump() { return false; }
+	virtual bool has_spatial_varying() { return false; }
 
 	vector<ShaderInput*> inputs;
 	vector<ShaderOutput*> outputs;
diff --git a/intern/cycles/render/nodes.h b/intern/cycles/render/nodes.h
index 31caf9507eb..054ae0f613c 100644
--- a/intern/cycles/render/nodes.h
+++ b/intern/cycles/render/nodes.h
@@ -209,6 +209,7 @@ public:
 	BsdfNode(bool scattering = false);
 	SHADER_NODE_BASE_CLASS(BsdfNode);
 
+	bool has_spatial_varying() { return true; }
 	void compile(SVMCompiler& compiler, ShaderInput *param1, ShaderInput *param2, ShaderInput *param3 = NULL, ShaderInput *param4 = NULL);
 
 	ClosureType closure;
@@ -280,6 +281,7 @@ public:
 	SHADER_NODE_CLASS(SubsurfaceScatteringNode)
 	bool has_surface_bssrdf() { return true; }
 	bool has_bssrdf_bump();
+	bool has_spatial_varying() { return true; }
 
 	static ShaderEnum falloff_enum;
 };
@@ -289,6 +291,7 @@ public:
 	SHADER_NODE_CLASS(EmissionNode)
 
 	bool has_surface_emission() { return true; }
+	bool has_spatial_varying() { return true; }
 
 	bool total_power;
 };
@@ -306,6 +309,8 @@ public:
 class AmbientOcclusionNode : public ShaderNode {
 public:
 	SHADER_NODE_CLASS(AmbientOcclusionNode)
+
+	bool has_spatial_varying() { return true; }
 };
 
 class VolumeNode : public ShaderNode {
@@ -340,12 +345,14 @@ class GeometryNode : public ShaderNode {
 public:
 	SHADER_NODE_CLASS(GeometryNode)
 	void attributes(Shader *shader, AttributeRequestSet *attributes);
+	bool has_spatial_varying() { return true; }
 };
 
 class TextureCoordinateNode : public ShaderNode {
 public:
 	SHADER_NODE_CLASS(TextureCoordinateNode)
 	void attributes(Shader *shader, AttributeRequestSet *attributes);
+	bool has_spatial_varying() { return true; }
 	
 	bool from_dupli;
 };
@@ -354,6 +361,7 @@ class UVMapNode : public ShaderNode {
 public:
 	SHADER_NODE_CLASS(UVMapNode)
 	void attributes(Shader *shader, AttributeRequestSet *attributes);
+	bool has_spatial_varying() { return true; }
 
 	ustring attribute;
 	bool from_dupli;
@@ -367,6 +375,7 @@ public:
 class LightFalloffNode : public ShaderNode {
 public:
 	SHADER_NODE_CLASS(LightFalloffNode)
+	bool has_spatial_varying() { return true; }
 };
 
 class ObjectInfoNode : public ShaderNode {
@@ -385,6 +394,7 @@ public:
 	SHADER_NODE_CLASS(HairInfoNode)
 
 	void attributes(Shader *shader, AttributeRequestSet *attributes);
+	bool has_spatial_varying() { return true; }
 };
 
 class ValueNode : public ShaderNode {
@@ -470,6 +480,7 @@ class AttributeNode : public ShaderNode {
 public:
 	SHADER_NODE_CLASS(AttributeNode)
 	void attributes(Shader *shader, AttributeRequestSet *attributes);
+	bool has_spatial_varying() { return true; }
 
 	ustring attribute;
 };
@@ -477,21 +488,25 @@ public:
 class CameraNode : public ShaderNode {
 public:
 	SHADER_NODE_CLASS(CameraNode)
+	bool has_spatial_varying() { return true; }
 };
 
 class FresnelNode : public ShaderNode {
 public:
 	SHADER_NODE_CLASS(FresnelNode)
+	bool has_spatial_varying() { return true; }
 };
 
 class LayerWeightNode : public ShaderNode {
 public:
 	SHADER_NODE_CLASS(LayerWeightNode)
+	bool has_spatial_varying() { return true; }
 };
 
 class WireframeNode : public ShaderNode {
 public:
 	SHADER_NODE_CLASS(WireframeNode)
+	bool has_spatial_varying() { return true; }
 	
 	bool use_pixel_size;
 };
@@ -548,6 +563,8 @@ public:
 class BumpNode : public ShaderNode {
 public:
 	SHADER_NODE_CLASS(BumpNode)
+	bool has_spatial_varying() { return true; }
+
 	bool invert;
 };
 
@@ -578,6 +595,10 @@ public:
 class OSLScriptNode : public ShaderNode {
 public:
 	SHADER_NODE_CLASS(OSLScriptNode)
+
+	/* ideally we could beter detect this, but we can't query this now */
+	bool has_spatial_varying() { return true; }
+
 	string filepath;
 	string bytecode_hash;
 	
@@ -591,6 +612,7 @@ class NormalMapNode : public ShaderNode {
 public:
 	SHADER_NODE_CLASS(NormalMapNode)
 	void attributes(Shader *shader, AttributeRequestSet *attributes);
+	bool has_spatial_varying() { return true; }
 
 	ustring space;
 	static ShaderEnum space_enum;
@@ -602,6 +624,7 @@ class TangentNode : public ShaderNode {
 public:
 	SHADER_NODE_CLASS(TangentNode)
 	void attributes(Shader *shader, AttributeRequestSet *attributes);
+	bool has_spatial_varying() { return true; }
 
 	ustring direction_type;
 	static ShaderEnum direction_type_enum;
diff --git a/intern/cycles/render/shader.cpp b/intern/cycles/render/shader.cpp
index 20f0fd7ed1e..b25673b36c3 100644
--- a/intern/cycles/render/shader.cpp
+++ b/intern/cycles/render/shader.cpp
@@ -53,6 +53,7 @@ Shader::Shader()
 	has_volume = false;
 	has_displacement = false;
 	has_bssrdf_bump = false;
+	has_heterogeneous_volume = false;
 
 	used = false;
 
@@ -249,7 +250,7 @@ void ShaderManager::device_update_common(Device *device, DeviceScene *dscene, Sc
 			 * the case with camera inside volumes too */
 			flag |= SD_HAS_TRANSPARENT_SHADOW;
 		}
-		if(shader->heterogeneous_volume)
+		if(shader->heterogeneous_volume && shader->has_heterogeneous_volume)
 			flag |= SD_HETEROGENEOUS_VOLUME;
 		if(shader->has_bssrdf_bump)
 			flag |= SD_HAS_BSSRDF_BUMP;
diff --git a/intern/cycles/render/shader.h b/intern/cycles/render/shader.h
index 5f87050fe19..874e8face7a 100644
--- a/intern/cycles/render/shader.h
+++ b/intern/cycles/render/shader.h
@@ -77,6 +77,7 @@ public:
 	bool has_surface_bssrdf;
 	bool has_converter_blackbody;
 	bool has_bssrdf_bump;
+	bool has_heterogeneous_volume;
 
 	/* requested mesh attributes */
 	AttributeRequestSet attributes;
diff --git a/intern/cycles/render/svm.cpp b/intern/cycles/render/svm.cpp
index 377da67b5a4..c004187a091 100644
--- a/intern/cycles/render/svm.cpp
+++ b/intern/cycles/render/svm.cpp
@@ -379,6 +379,18 @@ void SVMCompiler::find_dependencies(set<ShaderNode*>& dependencies, const set<Sh
 	}
 }
 
+void SVMCompiler::generate_node(ShaderNode *node, set<ShaderNode*>& done)
+{
+	node->compile(*this);
+	stack_clear_users(node, done);
+	stack_clear_temporary(node);
+
+	if(current_type == SHADER_TYPE_VOLUME) {
+		if(node->has_spatial_varying())
+			current_shader->has_heterogeneous_volume = true;
+	}
+}
+
 void SVMCompiler::generate_svm_nodes(const set<ShaderNode*>& nodes, set<ShaderNode*>& done)
 {
 	bool nodes_done;
@@ -400,9 +412,7 @@ void SVMCompiler::generate_svm_nodes(const set<ShaderNode*>& nodes, set<ShaderNo
 					if(node->has_converter_blackbody())
 					current_shader->has_converter_blackbody = true;
 
-					node->compile(*this);
-					stack_clear_users(node, done);
-					stack_clear_temporary(node);
+					generate_node(node, done);
 					done.insert(node);
 				}
 				else
@@ -485,9 +495,7 @@ void SVMCompiler::generate_closure(ShaderNode *node, set<ShaderNode*>& done)
 		}
 
 		/* compile closure itself */
-		node->compile(*this);
-		stack_clear_users(node, done);
-		stack_clear_temporary(node);
+		generate_node(node, done);
 
 		if(current_type == SHADER_TYPE_SURFACE) {
 			if(node->has_surface_emission())
@@ -550,9 +558,7 @@ void SVMCompiler::generate_multi_closure(ShaderNode *node, set<ShaderNode*>& don
 			mix_weight_offset = SVM_STACK_INVALID;
 
 		/* compile closure itself */
-		node->compile(*this);
-		stack_clear_users(node, done);
-		stack_clear_temporary(node);
+		generate_node(node, done);
 
 		mix_weight_offset = SVM_STACK_INVALID;
 
@@ -694,6 +700,7 @@ void SVMCompiler::compile(Shader *shader, vector<int4>& global_svm_nodes, int in
 	shader->has_converter_blackbody = false;
 	shader->has_volume = false;
 	shader->has_displacement = false;
+	shader->has_heterogeneous_volume = false;
 
 	/* generate surface shader */
 	compile_type(shader, shader->graph, SHADER_TYPE_SURFACE);
diff --git a/intern/cycles/render/svm.h b/intern/cycles/render/svm.h
index 3d84a67e173..069ba5247a2 100644
--- a/intern/cycles/render/svm.h
+++ b/intern/cycles/render/svm.h
@@ -124,6 +124,7 @@ protected:
 
 	/* single closure */
 	void find_dependencies(set<ShaderNode*>& dependencies, const set<ShaderNode*>& done, ShaderInput *input);
+	void generate_node(ShaderNode *node, set<ShaderNode*>& done);
 	void generate_svm_nodes(const set<ShaderNode*>& nodes, set<ShaderNode*>& done);
 	void generate_closure(ShaderNode *node, set<ShaderNode*>& done);