Fix T54105: random walk SSS missing in branched indirect paths.

Unify the path and branched path indirect SSS code. No performance impact
found on CUDA, for AMD split kernel the extra code was already there.

1 files changed, 36 insertions, 19 deletions

diff --git a/intern/cycles/kernel/kernel_path.h b/intern/cycles/kernel/kernel_path.h
index dbbb80ca37f..4728a25a3bc 100644
--- a/intern/cycles/kernel/kernel_path.h
+++ b/intern/cycles/kernel/kernel_path.h
@@ -400,6 +400,13 @@ ccl_device void kernel_path_indirect(KernelGlobals *kg,
                                      PathState *state,
                                      PathRadiance *L)
 {
+#ifdef __SUBSURFACE__
+	SubsurfaceIndirectRays ss_indirect;
+	kernel_path_subsurface_init_indirect(&ss_indirect);
+
+	for(;;) {
+#endif  /* __SUBSURFACE__ */
+
 	/* path iteration */
 	for(;;) {
 		/* Find intersection with objects in scene. */
@@ -485,29 +492,21 @@ ccl_device void kernel_path_indirect(KernelGlobals *kg,
 		}
 #endif  /* __AO__ */
 
+
 #ifdef __SUBSURFACE__
 		/* bssrdf scatter to a different location on the same object, replacing
 		 * the closures with a diffuse BSDF */
 		if(sd->flag & SD_BSSRDF) {
-			float bssrdf_u, bssrdf_v;
-			path_state_rng_2D(kg,
-			                  state,
-			                  PRNG_BSDF_U,
-			                  &bssrdf_u, &bssrdf_v);
-
-			const ShaderClosure *sc = shader_bssrdf_pick(sd, &throughput, &bssrdf_u);
-
-			/* do bssrdf scatter step if we picked a bssrdf closure */
-			if(sc) {
-				uint lcg_state = lcg_state_init(state, 0x68bc21eb);
-
-				subsurface_scatter_step(kg,
-				                        sd,
-				                        state,
-				                        sc,
-				                        &lcg_state,
-				                        bssrdf_u, bssrdf_v,
-				                        false);
+			if(kernel_path_subsurface_scatter(kg,
+			                                  sd,
+			                                  emission_sd,
+			                                  L,
+			                                  state,
+			                                  ray,
+			                                  &throughput,
+			                                  &ss_indirect))
+			{
+				break;
 			}
 		}
 #endif  /* __SUBSURFACE__ */
@@ -530,6 +529,24 @@ ccl_device void kernel_path_indirect(KernelGlobals *kg,
 		if(!kernel_path_surface_bounce(kg, sd, &throughput, state, &L->state, ray))
 			break;
 	}
+
+#ifdef __SUBSURFACE__
+		/* Trace indirect subsurface rays by restarting the loop. this uses less
+		 * stack memory than invoking kernel_path_indirect.
+		 */
+		if(ss_indirect.num_rays) {
+			kernel_path_subsurface_setup_indirect(kg,
+			                                      &ss_indirect,
+			                                      state,
+			                                      ray,
+			                                      L,
+			                                      &throughput);
+		}
+		else {
+			break;
+		}
+	}
+#endif  /* __SUBSURFACE__ */
 }
 
 #endif /* defined(__BRANCHED_PATH__) || defined(__BAKING__) */