Cycles: Don't re-generate blackbody/beckmann tables on every shaders update

This commit makes it so blackbody and beckmann lookup tables are stored on CPU
after being generated and then only being copied to the device if needed.

This solves lag of viewport update when tweaking shader tree by using 266KB of
CPU memory.

intern/cycles/render/blackbody.cpp

@@ -38,7 +38,7 @@
 
 CCL_NAMESPACE_BEGIN
 
-vector<float> blackbody_table()
+vector<float> blackbody_table_build()
 {
 	/* quoted from OSLs opcolor.cpp
 	In order to speed up the blackbody computation, we have a table

intern/cycles/render/blackbody.h

@@ -21,7 +21,7 @@
 
 CCL_NAMESPACE_BEGIN
 
-vector<float> blackbody_table();
+vector<float> blackbody_table_build();
 
 CCL_NAMESPACE_END
 

intern/cycles/render/shader.cpp

@@ -387,8 +387,10 @@ void ShaderManager::device_update_common(Device *device, DeviceScene *dscene, Sc
 	KernelTables *ktables = &dscene->data.tables;
 	
 	if(has_converter_blackbody && blackbody_table_offset == TABLE_OFFSET_INVALID) {
-		vector<float> table = blackbody_table();
-		blackbody_table_offset = scene->lookup_tables->add_table(dscene, table);
+		if(blackbody_table.size() == 0) {
+			blackbody_table = blackbody_table_build();
+		}
+		blackbody_table_offset = scene->lookup_tables->add_table(dscene, blackbody_table);
 		
 		ktables->blackbody_offset = (int)blackbody_table_offset;
 	}
@@ -399,10 +401,10 @@ void ShaderManager::device_update_common(Device *device, DeviceScene *dscene, Sc
 
 	/* beckmann lookup table */
 	if(beckmann_table_offset == TABLE_OFFSET_INVALID) {
-		vector<float> table;
-		beckmann_table_build(table);
-		beckmann_table_offset = scene->lookup_tables->add_table(dscene, table);
-		
+		if(beckmann_table.size() == 0) {
+			beckmann_table_build(beckmann_table);
+		}
+		beckmann_table_offset = scene->lookup_tables->add_table(dscene, beckmann_table);
 		ktables->beckmann_offset = (int)beckmann_table_offset;
 	}
 

intern/cycles/render/shader.h

@@ -170,6 +170,9 @@ protected:
 	typedef unordered_map<ustring, uint, ustringHash> AttributeIDMap;
 	AttributeIDMap unique_attribute_id;
 
+	vector<float> blackbody_table;
+	vector<float> beckmann_table;
+
 	size_t blackbody_table_offset;
 	size_t beckmann_table_offset;
 };