Cycles: Auto disable World MIS, if we only use a simple color.

When World MIS is enabled by the user, we now check if we actually need it.
In case of a simple node setup (no procedurals, no HDRs..) we auto disable MIS internally to save render time.

This change is important for upcoming default changes.

intern/cycles/render/light.cpp

@@ -556,13 +556,28 @@ void LightManager::device_update_points(Device *device, DeviceScene *dscene, Sce
 	if(scene->lights.size() == 0)
 		return;
 
-	/* remove background light? */
-	if(!(device->info.advanced_shading)) {
-		foreach(Light *light, scene->lights) {
-			if(light->type == LIGHT_BACKGROUND) {
+	/* Do we have a portal? */
+	bool has_portal = false;
+	foreach(Light *light, scene->lights) {
+		if(light->is_portal) {
+			has_portal = true;
+			break;
+		}
+	}
+
+	/* Remove background light:
+	 * - If unsupported on a device
+	 * - If we don't need it (no HDRs etc.)
+	 */
+	foreach(Light *light, scene->lights) {
+		if(light->type == LIGHT_BACKGROUND) {
+			Shader *shader = scene->shaders[scene->background->shader];
+			bool auto_disable_mis = (!has_portal && !shader->has_surface_spatial_varying);
+			if(!(device->info.advanced_shading) || auto_disable_mis) {
+				VLOG(1) << "Background MIS has been disabled. \n";
 				scene->lights.erase(std::remove(scene->lights.begin(), scene->lights.end(), light), scene->lights.end());
-				break;
 			}
+			break;
 		}
 	}
 
@@ -740,7 +755,7 @@ void LightManager::device_update_points(Device *device, DeviceScene *dscene, Sce
 
 void LightManager::device_update(Device *device, DeviceScene *dscene, Scene *scene, Progress& progress)
 {
-	VLOG(1) << "Total " << scene->lights.size() << " lights.";
+	int lights_size = scene->lights.size();
 
 	if(!need_update)
 		return;
@@ -764,6 +779,11 @@ void LightManager::device_update(Device *device, DeviceScene *dscene, Scene *sce
 	}
 
 	need_update = false;
+
+	if(lights_size != scene->lights.size())
+		VLOG(1) << "Total " << scene->lights.size() << " lights (" << lights_size << " before optimization).";
+	else
+		VLOG(1) << "Total " << scene->lights.size() << " lights.";
 }
 
 void LightManager::device_free(Device *device, DeviceScene *dscene)

intern/cycles/render/osl.cpp

@@ -570,14 +570,20 @@ void OSLCompiler::add(ShaderNode *node, const char *name, bool isfilepath)
 	/* test if we shader contains specific closures */
 	OSLShaderInfo *info = ((OSLShaderManager*)manager)->shader_loaded_info(name);
 
-	if(info && current_type == SHADER_TYPE_SURFACE) {
-		if(info->has_surface_emission)
-			current_shader->has_surface_emission = true;
-		if(info->has_surface_transparent)
-			current_shader->has_surface_transparent = true;
-		if(info->has_surface_bssrdf) {
-			current_shader->has_surface_bssrdf = true;
-			current_shader->has_bssrdf_bump = true; /* can't detect yet */
+	if(current_type == SHADER_TYPE_SURFACE) {
+		if(info) {
+			if(info->has_surface_emission)
+				current_shader->has_surface_emission = true;
+			if(info->has_surface_transparent)
+				current_shader->has_surface_transparent = true;
+			if(info->has_surface_bssrdf) {
+				current_shader->has_surface_bssrdf = true;
+				current_shader->has_bssrdf_bump = true; /* can't detect yet */
+			}
+		}
+
+		if(node->has_spatial_varying()) {
+			current_shader->has_surface_spatial_varying = true;
 		}
 	}
 	else if(current_type == SHADER_TYPE_VOLUME) {
@@ -752,6 +758,8 @@ void OSLCompiler::generate_nodes(const ShaderNodeSet& nodes)
 							current_shader->has_surface_emission = true;
 						if(node->has_surface_transparent())
 							current_shader->has_surface_transparent = true;
+						if(node->has_spatial_varying())
+							current_shader->has_surface_spatial_varying = true;
 						if(node->has_surface_bssrdf()) {
 							current_shader->has_surface_bssrdf = true;
 							if(node->has_bssrdf_bump())
@@ -839,6 +847,7 @@ void OSLCompiler::compile(Scene *scene, OSLGlobals *og, Shader *shader)
 		shader->has_bssrdf_bump = false;
 		shader->has_volume = false;
 		shader->has_displacement = false;
+		shader->has_surface_spatial_varying = false;
 		shader->has_volume_spatial_varying = false;
 		shader->has_object_dependency = false;
 		shader->has_integrator_dependency = false;

intern/cycles/render/shader.cpp

@@ -152,6 +152,7 @@ Shader::Shader()
 	has_volume = false;
 	has_displacement = false;
 	has_bssrdf_bump = false;
+	has_surface_spatial_varying = false;
 	has_volume_spatial_varying = false;
 	has_object_dependency = false;
 	has_integrator_dependency = false;

intern/cycles/render/shader.h

@@ -106,6 +106,7 @@ public:
 	bool has_displacement;
 	bool has_surface_bssrdf;
 	bool has_bssrdf_bump;
+	bool has_surface_spatial_varying;
 	bool has_volume_spatial_varying;
 	bool has_object_dependency;
 	bool has_integrator_dependency;

intern/cycles/render/svm.cpp

@@ -397,7 +397,11 @@ void SVMCompiler::generate_node(ShaderNode *node, ShaderNodeSet& done)
 	stack_clear_users(node, done);
 	stack_clear_temporary(node);
 
-	if(current_type == SHADER_TYPE_VOLUME) {
+	if(current_type == SHADER_TYPE_SURFACE) {
+		if(node->has_spatial_varying())
+			current_shader->has_surface_spatial_varying = true;
+	}
+	else if(current_type == SHADER_TYPE_VOLUME) {
 		if(node->has_spatial_varying())
 			current_shader->has_volume_spatial_varying = true;
 	}
@@ -761,6 +765,7 @@ void SVMCompiler::compile(Scene *scene,
 	shader->has_bssrdf_bump = false;
 	shader->has_volume = false;
 	shader->has_displacement = false;
+	shader->has_surface_spatial_varying = false;
 	shader->has_volume_spatial_varying = false;
 	shader->has_object_dependency = false;
 	shader->has_integrator_dependency = false;