Cycles: Stop lamp sampling if the lamp isn't visible

Both spot and area light have large areas where they're not visible.
Therefore, this patch stops the light sampling code when one of these cases (outside of the spotlight cone or behind the area light) occurs, before the lamp shader is evaluated.
In the case of the area light, the solid angle sampling can also be skipped.

In a test scene with Sample All Lights and 18 Area lamps and 9 Spot lamps that all point away from the area that the camera sees, render time drops from 12sec to 5sec.

Reviewers: brecht, sergey, dingto, juicyfruit

Differential Revision: https://developer.blender.org/D2216

1 files changed, 39 insertions, 49 deletions

diff --git a/intern/cycles/kernel/kernel_path_volume.h b/intern/cycles/kernel/kernel_path_volume.h
index 5fd4f2fad4c..0bb8f1c517f 100644
--- a/intern/cycles/kernel/kernel_path_volume.h
+++ b/intern/cycles/kernel/kernel_path_volume.h
@@ -46,17 +46,16 @@ ccl_device_inline void kernel_path_volume_connect_light(
 	light_ray.time = sd->time;
 #  endif
 
-	light_sample(kg, light_t, light_u, light_v, sd->time, sd->P, state->bounce, &ls);
-	if(ls.pdf == 0.0f)
-		return;
-	
-	if(direct_emission(kg, sd, emission_sd, &ls, state, &light_ray, &L_light, &is_lamp)) {
-		/* trace shadow ray */
-		float3 shadow;
+	if(light_sample(kg, light_t, light_u, light_v, sd->time, sd->P, state->bounce, &ls))
+	{
+		if(direct_emission(kg, sd, emission_sd, &ls, state, &light_ray, &L_light, &is_lamp)) {
+			/* trace shadow ray */
+			float3 shadow;
 
-		if(!shadow_blocked(kg, emission_sd, state, &light_ray, &shadow)) {
-			/* accumulate */
-			path_radiance_accum_light(L, throughput, &L_light, shadow, 1.0f, state->bounce, is_lamp);
+			if(!shadow_blocked(kg, emission_sd, state, &light_ray, &shadow)) {
+				/* accumulate */
+				path_radiance_accum_light(L, throughput, &L_light, shadow, 1.0f, state->bounce, is_lamp);
+			}
 		}
 	}
 #endif
@@ -146,7 +145,7 @@ ccl_device void kernel_branched_path_volume_connect_light(KernelGlobals *kg, RNG
 				path_branched_rng_2D(kg, &lamp_rng, state, j, num_samples, PRNG_LIGHT_U, &light_u, &light_v);
 
 				LightSample ls;
-				lamp_light_sample(kg, i, light_u, light_v, ray->P, &ls);		
+				lamp_light_sample(kg, i, light_u, light_v, ray->P, &ls);
 
 				float3 tp = throughput;
 
@@ -156,23 +155,20 @@ ccl_device void kernel_branched_path_volume_connect_light(KernelGlobals *kg, RNG
 
 				VolumeIntegrateResult result = kernel_volume_decoupled_scatter(kg,
 					state, ray, sd, &tp, rphase, rscatter, segment, (ls.t != FLT_MAX)? &ls.P: NULL, false);
-					
+
 				(void)result;
 				kernel_assert(result == VOLUME_PATH_SCATTERED);
 
 				/* todo: split up light_sample so we don't have to call it again with new position */
-				lamp_light_sample(kg, i, light_u, light_v, sd->P, &ls);
-
-				if(ls.pdf == 0.0f)
-					continue;
-
-				if(direct_emission(kg, sd, emission_sd, &ls, state, &light_ray, &L_light, &is_lamp)) {
-					/* trace shadow ray */
-					float3 shadow;
-
-					if(!shadow_blocked(kg, emission_sd, state, &light_ray, &shadow)) {
-						/* accumulate */
-						path_radiance_accum_light(L, tp*num_samples_inv, &L_light, shadow, num_samples_inv, state->bounce, is_lamp);
+				if(lamp_light_sample(kg, i, light_u, light_v, sd->P, &ls)) {
+					if(direct_emission(kg, sd, emission_sd, &ls, state, &light_ray, &L_light, &is_lamp)) {
+						/* trace shadow ray */
+						float3 shadow;
+
+						if(!shadow_blocked(kg, emission_sd, state, &light_ray, &shadow)) {
+							/* accumulate */
+							path_radiance_accum_light(L, tp*num_samples_inv, &L_light, shadow, num_samples_inv, state->bounce, is_lamp);
+						}
 					}
 				}
 			}
@@ -212,18 +208,15 @@ 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, state->bounce, &ls);
-
-				if(ls.pdf == 0.0f)
-					continue;
-
-				if(direct_emission(kg, sd, emission_sd, &ls, state, &light_ray, &L_light, &is_lamp)) {
-					/* trace shadow ray */
-					float3 shadow;
-
-					if(!shadow_blocked(kg, emission_sd, state, &light_ray, &shadow)) {
-						/* accumulate */
-						path_radiance_accum_light(L, tp*num_samples_inv, &L_light, shadow, num_samples_inv, state->bounce, is_lamp);
+				if(light_sample(kg, light_t, light_u, light_v, sd->time, sd->P, state->bounce, &ls)) {
+					if(direct_emission(kg, sd, emission_sd, &ls, state, &light_ray, &L_light, &is_lamp)) {
+						/* trace shadow ray */
+						float3 shadow;
+
+						if(!shadow_blocked(kg, emission_sd, state, &light_ray, &shadow)) {
+							/* accumulate */
+							path_radiance_accum_light(L, tp*num_samples_inv, &L_light, shadow, num_samples_inv, state->bounce, is_lamp);
+						}
 					}
 				}
 			}
@@ -251,19 +244,16 @@ 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, state->bounce, &ls);
-
-		if(ls.pdf == 0.0f)
-			return;
-
-		/* sample random light */
-		if(direct_emission(kg, sd, emission_sd, &ls, state, &light_ray, &L_light, &is_lamp)) {
-			/* trace shadow ray */
-			float3 shadow;
-
-			if(!shadow_blocked(kg, emission_sd, state, &light_ray, &shadow)) {
-				/* accumulate */
-				path_radiance_accum_light(L, tp, &L_light, shadow, 1.0f, state->bounce, is_lamp);
+		if(light_sample(kg, light_t, light_u, light_v, sd->time, sd->P, state->bounce, &ls)) {
+			/* sample random light */
+			if(direct_emission(kg, sd, emission_sd, &ls, state, &light_ray, &L_light, &is_lamp)) {
+				/* trace shadow ray */
+				float3 shadow;
+
+				if(!shadow_blocked(kg, emission_sd, state, &light_ray, &shadow)) {
+					/* accumulate */
+					path_radiance_accum_light(L, tp, &L_light, shadow, 1.0f, state->bounce, is_lamp);
+				}
 			}
 		}
 	}