Cycles: Add "Max Bounce" control for lamps

With this setting, we can limit the influence of a lamp to a certain amount of bounces.
0 = Only direct light contribution
1 = 1 light bounce
...

Differential revision: https://developer.blender.org/D860

You can find an example render in the release logs: http://wiki.blender.org/index.php/Dev:Ref/Release_Notes/2.73/Cycles

intern/cycles/blender/addon/properties.py

@@ -653,6 +653,12 @@ class CyclesLampSettings(bpy.types.PropertyGroup):
                 min=1, max=10000,
                 default=1,
                 )
+        cls.max_bounces = IntProperty(
+                name="Max Bounces",
+                description="Maximum number of bounces the light will contribute to the render",
+                min=0, max=1024,
+                default=1024,
+                )
         cls.use_multiple_importance_sampling = BoolProperty(
                 name="Multiple Importance Sample",
                 description="Use multiple importance sampling for the lamp, "

intern/cycles/blender/addon/ui.py

@@ -729,11 +729,11 @@ class CyclesLamp_PT_lamp(CyclesButtonsPanel, Panel):
 
         if cscene.progressive == 'BRANCHED_PATH':
             col.prop(clamp, "samples")
+        col.prop(clamp, "max_bounces")
 
         col = split.column()
         col.prop(clamp, "cast_shadow")
-
+        col.prop(clamp, "use_multiple_importance_sampling")
-        layout.prop(clamp, "use_multiple_importance_sampling")
 
         if lamp.type == 'HEMI':
             layout.label(text="Not supported, interpreted as sun lamp")

intern/cycles/blender/blender_object.cpp

@@ -168,6 +168,8 @@ void BlenderSync::sync_light(BL::Object b_parent, int persistent_id[OBJECT_PERSI
 	else
 		light->samples = samples;
 
+	light->max_bounces = get_int(clamp, "max_bounces");
+
 	/* visibility */
 	uint visibility = object_ray_visibility(b_ob);
 	light->use_diffuse = (visibility & PATH_RAY_DIFFUSE) != 0;

intern/cycles/kernel/kernel_light.h

@@ -648,7 +648,13 @@ ccl_device int light_distribution_sample(KernelGlobals *kg, float randt)
 
 /* Generic Light */
 
-ccl_device void light_sample(KernelGlobals *kg, float randt, float randu, float randv, float time, float3 P, LightSample *ls)
+ccl_device bool light_select_reached_max_bounces(KernelGlobals *kg, int index, int bounce)
+{
+	float4 data4 = kernel_tex_fetch(__light_data, index*LIGHT_SIZE + 4);
+	return (bounce > __float_as_int(data4.x));
+}
+
+ccl_device void light_sample(KernelGlobals *kg, float randt, float randu, float randv, float time, float3 P, int bounce, LightSample *ls)
 {
 	/* sample index */
 	int index = light_distribution_sample(kg, randt);
@@ -670,6 +676,12 @@ ccl_device void light_sample(KernelGlobals *kg, float randt, float randu, float
 	}
 	else {
 		int lamp = -prim-1;
+
+		if(UNLIKELY(light_select_reached_max_bounces(kg, lamp, bounce))) {
+			ls->pdf = 0.0f;
+			return;
+		}
+
 		lamp_light_sample(kg, lamp, randu, randv, P, ls);
 	}
 }

intern/cycles/kernel/kernel_path_surface.h

@@ -38,6 +38,9 @@ ccl_device void kernel_branched_path_surface_connect_light(KernelGlobals *kg, RN
 	if(sample_all_lights) {
 		/* lamp sampling */
 		for(int i = 0; i < kernel_data.integrator.num_all_lights; i++) {
+			if(UNLIKELY(light_select_reached_max_bounces(kg, i, state->bounce)))
+			   continue;
+
 			int num_samples = ceil_to_int(num_samples_adjust*light_select_num_samples(kg, i));
 			float num_samples_inv = num_samples_adjust/(num_samples*kernel_data.integrator.num_all_lights);
 			RNG lamp_rng = cmj_hash(*rng, i);
@@ -82,7 +85,7 @@ ccl_device void kernel_branched_path_surface_connect_light(KernelGlobals *kg, RN
 					light_t = 0.5f*light_t;
 
 				LightSample ls;
-				light_sample(kg, light_t, light_u, light_v, sd->time, sd->P, &ls);
+				light_sample(kg, light_t, light_u, light_v, sd->time, sd->P, state->bounce, &ls);
 
 				if(direct_emission(kg, sd, &ls, &light_ray, &L_light, &is_lamp, state->bounce, state->transparent_bounce)) {
 					/* trace shadow ray */
@@ -103,7 +106,7 @@ ccl_device void kernel_branched_path_surface_connect_light(KernelGlobals *kg, RN
 		path_state_rng_2D(kg, rng, state, PRNG_LIGHT_U, &light_u, &light_v);
 
 		LightSample ls;
-		light_sample(kg, light_t, light_u, light_v, sd->time, sd->P, &ls);
+		light_sample(kg, light_t, light_u, light_v, sd->time, sd->P, state->bounce, &ls);
 
 		/* sample random light */
 		if(direct_emission(kg, sd, &ls, &light_ray, &L_light, &is_lamp, state->bounce, state->transparent_bounce)) {
@@ -200,7 +203,7 @@ ccl_device_inline void kernel_path_surface_connect_light(KernelGlobals *kg, RNG
 #endif
 
 	LightSample ls;
-	light_sample(kg, light_t, light_u, light_v, sd->time, sd->P, &ls);
+	light_sample(kg, light_t, light_u, light_v, sd->time, sd->P, state->bounce, &ls);
 
 	if(direct_emission(kg, sd, &ls, &light_ray, &L_light, &is_lamp, state->bounce, state->transparent_bounce)) {
 		/* trace shadow ray */

intern/cycles/kernel/kernel_path_volume.h

@@ -40,7 +40,7 @@ ccl_device void kernel_path_volume_connect_light(KernelGlobals *kg, RNG *rng,
 	light_ray.time = sd->time;
 #endif
 
-	light_sample(kg, light_t, light_u, light_v, sd->time, sd->P, &ls);
+	light_sample(kg, light_t, light_u, light_v, sd->time, sd->P, state->bounce, &ls);
 	if(ls.pdf == 0.0f)
 		return;
 	
@@ -124,6 +124,9 @@ ccl_device void kernel_branched_path_volume_connect_light(KernelGlobals *kg, RNG
 	if(sample_all_lights) {
 		/* lamp sampling */
 		for(int i = 0; i < kernel_data.integrator.num_all_lights; i++) {
+			if(UNLIKELY(light_select_reached_max_bounces(kg, i, state->bounce)))
+				continue;
+
 			int num_samples = ceil_to_int(num_samples_adjust*light_select_num_samples(kg, i));
 			float num_samples_inv = num_samples_adjust/(num_samples*kernel_data.integrator.num_all_lights);
 			RNG lamp_rng = cmj_hash(*rng, i);
@@ -188,7 +191,7 @@ ccl_device void kernel_branched_path_volume_connect_light(KernelGlobals *kg, RNG
 					light_t = 0.5f*light_t;
 
 				LightSample ls;
-				light_sample(kg, light_t, light_u, light_v, sd->time, ray->P, &ls);
+				light_sample(kg, light_t, light_u, light_v, sd->time, ray->P, state->bounce, &ls);
 
 				float3 tp = throughput;
 
@@ -203,7 +206,7 @@ ccl_device void kernel_branched_path_volume_connect_light(KernelGlobals *kg, RNG
 				kernel_assert(result == VOLUME_PATH_SCATTERED);
 
 				/* todo: split up light_sample so we don't have to call it again with new position */
-				light_sample(kg, light_t, light_u, light_v, sd->time, sd->P, &ls);
+				light_sample(kg, light_t, light_u, light_v, sd->time, sd->P, state->bounce, &ls);
 
 				if(ls.pdf == 0.0f)
 					continue;
@@ -227,7 +230,7 @@ ccl_device void kernel_branched_path_volume_connect_light(KernelGlobals *kg, RNG
 		path_state_rng_2D(kg, rng, state, PRNG_LIGHT_U, &light_u, &light_v);
 
 		LightSample ls;
-		light_sample(kg, light_t, light_u, light_v, sd->time, ray->P, &ls);
+		light_sample(kg, light_t, light_u, light_v, sd->time, ray->P, state->bounce, &ls);
 
 		float3 tp = throughput;
 
@@ -242,7 +245,7 @@ ccl_device void kernel_branched_path_volume_connect_light(KernelGlobals *kg, RNG
 		kernel_assert(result == VOLUME_PATH_SCATTERED);
 
 		/* todo: split up light_sample so we don't have to call it again with new position */
-		light_sample(kg, light_t, light_u, light_v, sd->time, sd->P, &ls);
+		light_sample(kg, light_t, light_u, light_v, sd->time, sd->P, state->bounce, &ls);
 
 		if(ls.pdf == 0.0f)
 			return;

intern/cycles/kernel/kernel_types.h

@@ -29,7 +29,7 @@ CCL_NAMESPACE_BEGIN
 /* constants */
 #define OBJECT_SIZE 		11
 #define OBJECT_VECTOR_SIZE	6
-#define LIGHT_SIZE			4
+#define LIGHT_SIZE			5
 #define FILTER_TABLE_SIZE	256
 #define RAMP_TABLE_SIZE		256
 #define PARTICLE_SIZE 		5

intern/cycles/render/light.cpp

@@ -125,6 +125,7 @@ Light::Light()
 
 	shader = 0;
 	samples = 1;
+	max_bounces = 1024;
 }
 
 void Light::tag_update(Scene *scene)
@@ -489,6 +490,7 @@ void LightManager::device_update_points(Device *device, DeviceScene *dscene, Sce
 		float3 co = light->co;
 		int shader_id = scene->shader_manager->get_shader_id(scene->lights[i]->shader);
 		float samples = __int_as_float(light->samples);
+		float max_bounces = __int_as_float(light->max_bounces);
 
 		if(!light->cast_shadow)
 			shader_id &= ~SHADER_CAST_SHADOW;
@@ -523,6 +525,7 @@ void LightManager::device_update_points(Device *device, DeviceScene *dscene, Sce
 			light_data[i*LIGHT_SIZE + 1] = make_float4(__int_as_float(shader_id), radius, invarea, 0.0f);
 			light_data[i*LIGHT_SIZE + 2] = make_float4(0.0f, 0.0f, 0.0f, 0.0f);
 			light_data[i*LIGHT_SIZE + 3] = make_float4(samples, 0.0f, 0.0f, 0.0f);
+			light_data[i*LIGHT_SIZE + 4] = make_float4(max_bounces, 0.0f, 0.0f, 0.0f);
 		}
 		else if(light->type == LIGHT_DISTANT) {
 			shader_id &= ~SHADER_AREA_LIGHT;
@@ -544,6 +547,7 @@ void LightManager::device_update_points(Device *device, DeviceScene *dscene, Sce
 			light_data[i*LIGHT_SIZE + 1] = make_float4(__int_as_float(shader_id), radius, cosangle, invarea);
 			light_data[i*LIGHT_SIZE + 2] = make_float4(0.0f, 0.0f, 0.0f, 0.0f);
 			light_data[i*LIGHT_SIZE + 3] = make_float4(samples, 0.0f, 0.0f, 0.0f);
+			light_data[i*LIGHT_SIZE + 4] = make_float4(max_bounces, 0.0f, 0.0f, 0.0f);
 		}
 		else if(light->type == LIGHT_BACKGROUND) {
 			uint visibility = scene->background->visibility;
@@ -572,6 +576,7 @@ void LightManager::device_update_points(Device *device, DeviceScene *dscene, Sce
 			light_data[i*LIGHT_SIZE + 1] = make_float4(__int_as_float(shader_id), 0.0f, 0.0f, 0.0f);
 			light_data[i*LIGHT_SIZE + 2] = make_float4(0.0f, 0.0f, 0.0f, 0.0f);
 			light_data[i*LIGHT_SIZE + 3] = make_float4(samples, 0.0f, 0.0f, 0.0f);
+			light_data[i*LIGHT_SIZE + 4] = make_float4(max_bounces, 0.0f, 0.0f, 0.0f);
 		}
 		else if(light->type == LIGHT_AREA) {
 			float3 axisu = light->axisu*(light->sizeu*light->size);
@@ -590,6 +595,7 @@ void LightManager::device_update_points(Device *device, DeviceScene *dscene, Sce
 			light_data[i*LIGHT_SIZE + 1] = make_float4(__int_as_float(shader_id), axisu.x, axisu.y, axisu.z);
 			light_data[i*LIGHT_SIZE + 2] = make_float4(invarea, axisv.x, axisv.y, axisv.z);
 			light_data[i*LIGHT_SIZE + 3] = make_float4(samples, dir.x, dir.y, dir.z);
+			light_data[i*LIGHT_SIZE + 4] = make_float4(max_bounces, 0.0f, 0.0f, 0.0f);
 		}
 		else if(light->type == LIGHT_SPOT) {
 			shader_id &= ~SHADER_AREA_LIGHT;
@@ -610,6 +616,7 @@ void LightManager::device_update_points(Device *device, DeviceScene *dscene, Sce
 			light_data[i*LIGHT_SIZE + 1] = make_float4(__int_as_float(shader_id), radius, invarea, spot_angle);
 			light_data[i*LIGHT_SIZE + 2] = make_float4(spot_smooth, dir.x, dir.y, dir.z);
 			light_data[i*LIGHT_SIZE + 3] = make_float4(samples, 0.0f, 0.0f, 0.0f);
+			light_data[i*LIGHT_SIZE + 4] = make_float4(max_bounces, 0.0f, 0.0f, 0.0f);
 		}
 	}
 	

intern/cycles/render/light.h

@@ -58,6 +58,7 @@ public:
 
 	int shader;
 	int samples;
+	int max_bounces;
 
 	void tag_update(Scene *scene);
 };