Cycles Volume Render: add flags to quickly detect when objects have a volume shader.

Referenced by issue #39089, Double render times with Cycles 2.69 vs 2.70RC

intern/cycles/kernel/kernel_emission.h

@@ -225,7 +225,7 @@ ccl_device_noinline bool indirect_lamp_emission(KernelGlobals *kg, Ray *ray, int
 ccl_device_noinline float3 indirect_background(KernelGlobals *kg, Ray *ray, int path_flag, float bsdf_pdf, int bounce)
 {
 #ifdef __BACKGROUND__
-	int shader = kernel_data.background.shader;
+	int shader = kernel_data.background.surface_shader;
 
 	/* use visibility flag to skip lights */
 	if(shader & SHADER_EXCLUDE_ANY) {

intern/cycles/kernel/kernel_shader.h

@@ -376,7 +376,7 @@ ccl_device_inline void shader_setup_from_background(KernelGlobals *kg, ShaderDat
 	sd->N = -ray->D;
 	sd->Ng = -ray->D;
 	sd->I = -ray->D;
-	sd->shader = kernel_data.background.shader;
+	sd->shader = kernel_data.background.surface_shader;
 	sd->flag = kernel_tex_fetch(__shader_flag, (sd->shader & SHADER_MASK)*2);
 #ifdef __OBJECT_MOTION__
 	sd->time = ray->time;

intern/cycles/kernel/kernel_types.h

@@ -46,6 +46,8 @@ CCL_NAMESPACE_BEGIN
 
 #define TEX_NUM_FLOAT_IMAGES	5
 
+#define SHADER_NO_ID			-1
+
 /* device capabilities */
 #ifdef __KERNEL_CPU__
 #define __KERNEL_SHADING__
@@ -502,13 +504,14 @@ enum ShaderDataFlag {
 	SD_USE_MIS = 512,					/* direct light sample */
 	SD_HAS_TRANSPARENT_SHADOW = 1024,	/* has transparent shadow */
 	SD_HAS_VOLUME = 2048,				/* has volume shader */
-	SD_HOMOGENEOUS_VOLUME = 4096,		/* has homogeneous volume */
-	SD_HAS_BSSRDF_BUMP = 8192,			/* bssrdf normal uses bump */
+	SD_HAS_ONLY_VOLUME = 4096,			/* has only volume shader, no surface */
+	SD_HOMOGENEOUS_VOLUME = 8192,		/* has homogeneous volume */
+	SD_HAS_BSSRDF_BUMP = 16384,			/* bssrdf normal uses bump */
 
 	/* object flags */
-	SD_HOLDOUT_MASK = 16384,			/* holdout for camera rays */
-	SD_OBJECT_MOTION = 32768,			/* has object motion blur */
-	SD_TRANSFORM_APPLIED = 65536 		/* vertices have transform applied */
+	SD_HOLDOUT_MASK = 32768,			/* holdout for camera rays */
+	SD_OBJECT_MOTION = 65536,			/* has object motion blur */
+	SD_TRANSFORM_APPLIED = 131072 		/* vertices have transform applied */
 };
 
 struct KernelGlobals;
@@ -704,12 +707,15 @@ typedef struct KernelFilm {
 
 typedef struct KernelBackground {
 	/* only shader index */
-	int shader;
+	int surface_shader;
+	int volume_shader;
 	int transparent;
+	int pad;
 
 	/* ambient occlusion */
 	float ao_factor;
 	float ao_distance;
+	float ao_pad1, ao_pad2;
 } KernelBackground;
 
 typedef struct KernelIntegrator {
@@ -765,8 +771,8 @@ typedef struct KernelIntegrator {
 	/* sampler */
 	int sampling_pattern;
 
-	/* padding */
-	int pad;
+	/* volume render */
+	int use_volumes;
 } KernelIntegrator;
 
 typedef struct KernelBVH {

intern/cycles/render/background.cpp

@@ -65,16 +65,21 @@ void Background::device_update(Device *device, DeviceScene *dscene, Scene *scene
 	kbackground->ao_distance = ao_distance;
 
 	kbackground->transparent = transparent;
-	kbackground->shader = scene->shader_manager->get_shader_id(shader);
+	kbackground->surface_shader = scene->shader_manager->get_shader_id(shader);
+
+	if(scene->shaders[shader]->has_volume)
+		kbackground->volume_shader = kbackground->surface_shader;
+	else
+		kbackground->volume_shader = SHADER_NO_ID;
 
 	if(!(visibility & PATH_RAY_DIFFUSE))
-		kbackground->shader |= SHADER_EXCLUDE_DIFFUSE;
+		kbackground->surface_shader |= SHADER_EXCLUDE_DIFFUSE;
 	if(!(visibility & PATH_RAY_GLOSSY))
-		kbackground->shader |= SHADER_EXCLUDE_GLOSSY;
+		kbackground->surface_shader |= SHADER_EXCLUDE_GLOSSY;
 	if(!(visibility & PATH_RAY_TRANSMIT))
-		kbackground->shader |= SHADER_EXCLUDE_TRANSMIT;
+		kbackground->surface_shader |= SHADER_EXCLUDE_TRANSMIT;
 	if(!(visibility & PATH_RAY_CAMERA))
-		kbackground->shader |= SHADER_EXCLUDE_CAMERA;
+		kbackground->surface_shader |= SHADER_EXCLUDE_CAMERA;
 
 	need_update = false;
 }

intern/cycles/render/shader.cpp

@@ -218,6 +218,7 @@ void ShaderManager::device_update_common(Device *device, DeviceScene *dscene, Sc
 	uint *shader_flag = dscene->shader_flag.resize(shader_flag_size);
 	uint i = 0;
 	bool has_converter_blackbody = false;
+	bool has_volumes = false;
 
 	foreach(Shader *shader, scene->shaders) {
 		uint flag = 0;
@@ -226,8 +227,19 @@ void ShaderManager::device_update_common(Device *device, DeviceScene *dscene, Sc
 			flag |= SD_USE_MIS;
 		if(shader->has_surface_transparent && shader->use_transparent_shadow)
 			flag |= SD_HAS_TRANSPARENT_SHADOW;
-		if(shader->has_volume)
+		if(shader->has_volume) {
 			flag |= SD_HAS_VOLUME;
+			has_volumes = true;
+
+			/* in this case we can assume transparent surface */
+			if(!shader->has_surface)
+				flag |= SD_HAS_ONLY_VOLUME;
+
+			/* todo: this could check more fine grained, to skip useless volumes
+			 * enclosed inside an opaque bsdf, although we still need to handle
+			 * the case with camera inside volumes too */
+			flag |= SD_HAS_TRANSPARENT_SHADOW;
+		}
 		if(shader->homogeneous_volume)
 			flag |= SD_HOMOGENEOUS_VOLUME;
 		if(shader->has_bssrdf_bump)
@@ -263,6 +275,9 @@ void ShaderManager::device_update_common(Device *device, DeviceScene *dscene, Sc
 		blackbody_table_offset = TABLE_OFFSET_INVALID;
 	}
 
+	/* volumes */
+	KernelIntegrator *kintegrator = &dscene->data.integrator;
+	kintegrator->use_volumes = has_volumes;
 }
 
 void ShaderManager::device_free_common(Device *device, DeviceScene *dscene, Scene *scene)