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, 27 insertions, 126 deletions

diff --git a/intern/cycles/kernel/kernel_subsurface.h b/intern/cycles/kernel/kernel_subsurface.h
index 80dda31c61e..134f362f5e6 100644
--- a/intern/cycles/kernel/kernel_subsurface.h
+++ b/intern/cycles/kernel/kernel_subsurface.h
@@ -69,44 +69,42 @@ ccl_device_inline float3 subsurface_scatter_eval(ShaderData *sd,
 }
 
 /* replace closures with a single diffuse bsdf closure after scatter step */
-ccl_device void subsurface_scatter_setup_diffuse_bsdf(KernelGlobals *kg, ShaderData *sd, const ShaderClosure *sc, float3 weight, bool hit, float3 N)
+ccl_device void subsurface_scatter_setup_diffuse_bsdf(KernelGlobals *kg, ShaderData *sd, const ShaderClosure *sc, float3 weight, float3 N)
 {
 	sd->flag &= ~SD_CLOSURE_FLAGS;
 	sd->num_closure = 0;
 	sd->num_closure_left = kernel_data.integrator.max_closures;
 
-	if(hit) {
-		Bssrdf *bssrdf = (Bssrdf *)sc;
+	Bssrdf *bssrdf = (Bssrdf *)sc;
 #ifdef __PRINCIPLED__
-		if(bssrdf->type == CLOSURE_BSSRDF_PRINCIPLED_ID ||
-		   bssrdf->type == CLOSURE_BSSRDF_PRINCIPLED_RANDOM_WALK_ID)
-		{
-			PrincipledDiffuseBsdf *bsdf = (PrincipledDiffuseBsdf*)bsdf_alloc(sd, sizeof(PrincipledDiffuseBsdf), weight);
-
-			if(bsdf) {
-				bsdf->N = N;
-				bsdf->roughness = bssrdf->roughness;
-				sd->flag |= bsdf_principled_diffuse_setup(bsdf);
-
-				/* replace CLOSURE_BSDF_PRINCIPLED_DIFFUSE_ID with this special ID so render passes
-				 * can recognize it as not being a regular Disney principled diffuse closure */
-				bsdf->type = CLOSURE_BSDF_BSSRDF_PRINCIPLED_ID;
-			}
+	if(bssrdf->type == CLOSURE_BSSRDF_PRINCIPLED_ID ||
+	   bssrdf->type == CLOSURE_BSSRDF_PRINCIPLED_RANDOM_WALK_ID)
+	{
+		PrincipledDiffuseBsdf *bsdf = (PrincipledDiffuseBsdf*)bsdf_alloc(sd, sizeof(PrincipledDiffuseBsdf), weight);
+
+		if(bsdf) {
+			bsdf->N = N;
+			bsdf->roughness = bssrdf->roughness;
+			sd->flag |= bsdf_principled_diffuse_setup(bsdf);
+
+			/* replace CLOSURE_BSDF_PRINCIPLED_DIFFUSE_ID with this special ID so render passes
+			 * can recognize it as not being a regular Disney principled diffuse closure */
+			bsdf->type = CLOSURE_BSDF_BSSRDF_PRINCIPLED_ID;
 		}
-		else if(CLOSURE_IS_BSDF_BSSRDF(bssrdf->type) ||
-		        CLOSURE_IS_BSSRDF(bssrdf->type))
+	}
+	else if(CLOSURE_IS_BSDF_BSSRDF(bssrdf->type) ||
+			CLOSURE_IS_BSSRDF(bssrdf->type))
 #endif  /* __PRINCIPLED__ */
-		{
-			DiffuseBsdf *bsdf = (DiffuseBsdf*)bsdf_alloc(sd, sizeof(DiffuseBsdf), weight);
+	{
+		DiffuseBsdf *bsdf = (DiffuseBsdf*)bsdf_alloc(sd, sizeof(DiffuseBsdf), weight);
 
-			if(bsdf) {
-				bsdf->N = N;
-				sd->flag |= bsdf_diffuse_setup(bsdf);
+		if(bsdf) {
+			bsdf->N = N;
+			sd->flag |= bsdf_diffuse_setup(bsdf);
 
-				/* replace CLOSURE_BSDF_DIFFUSE_ID with this special ID so render passes
-				 * can recognize it as not being a regular diffuse closure */
-				bsdf->type = CLOSURE_BSDF_BSSRDF_ID;
-			}
+			/* replace CLOSURE_BSDF_DIFFUSE_ID with this special ID so render passes
+			 * can recognize it as not being a regular diffuse closure */
+			bsdf->type = CLOSURE_BSDF_BSSRDF_ID;
 		}
 	}
 }
@@ -334,104 +332,7 @@ ccl_device_noinline void subsurface_scatter_multi_setup(
 	subsurface_color_bump_blur(kg, sd, state, &weight, &N);
 
 	/* Setup diffuse BSDF. */
-	subsurface_scatter_setup_diffuse_bsdf(kg, sd, sc, weight, true, N);
-}
-
-/* subsurface scattering step, from a point on the surface to another nearby point on the same object */
-ccl_device void subsurface_scatter_step(KernelGlobals *kg, ShaderData *sd, ccl_addr_space PathState *state,
-	const ShaderClosure *sc, uint *lcg_state, float disk_u, float disk_v, bool all)
-{
-	float3 eval = make_float3(0.0f, 0.0f, 0.0f);
-
-	/* pick random axis in local frame and point on disk */
-	float3 disk_N, disk_T, disk_B;
-	float pick_pdf_N, pick_pdf_T, pick_pdf_B;
-
-	disk_N = sd->Ng;
-	make_orthonormals(disk_N, &disk_T, &disk_B);
-
-	if(disk_v < 0.5f) {
-		pick_pdf_N = 0.5f;
-		pick_pdf_T = 0.25f;
-		pick_pdf_B = 0.25f;
-		disk_v *= 2.0f;
-	}
-	else if(disk_v < 0.75f) {
-		float3 tmp = disk_N;
-		disk_N = disk_T;
-		disk_T = tmp;
-		pick_pdf_N = 0.25f;
-		pick_pdf_T = 0.5f;
-		pick_pdf_B = 0.25f;
-		disk_v = (disk_v - 0.5f)*4.0f;
-	}
-	else {
-		float3 tmp = disk_N;
-		disk_N = disk_B;
-		disk_B = tmp;
-		pick_pdf_N = 0.25f;
-		pick_pdf_T = 0.25f;
-		pick_pdf_B = 0.5f;
-		disk_v = (disk_v - 0.75f)*4.0f;
-	}
-
-	/* sample point on disk */
-	float phi = M_2PI_F * disk_v;
-	float disk_height, disk_r;
-
-	bssrdf_sample(sc, disk_u, &disk_r, &disk_height);
-
-	float3 disk_P = (disk_r*cosf(phi)) * disk_T + (disk_r*sinf(phi)) * disk_B;
-
-	/* create ray */
-	Ray ray;
-	ray.P = sd->P + disk_N*disk_height + disk_P;
-	ray.D = -disk_N;
-	ray.t = 2.0f*disk_height;
-	ray.dP = sd->dP;
-	ray.dD = differential3_zero();
-	ray.time = sd->time;
-
-	/* intersect with the same object. if multiple intersections are
-	 * found it will randomly pick one of them */
-	LocalIntersection ss_isect;
-	scene_intersect_local(kg, ray, &ss_isect, sd->object, lcg_state, 1);
-
-	/* evaluate bssrdf */
-	if(ss_isect.num_hits > 0) {
-		float3 origP = sd->P;
-
-		/* Workaround for AMD GPU OpenCL compiler. Most probably cache bypass issue. */
-#if defined(__SPLIT_KERNEL__) && defined(__KERNEL_OPENCL_AMD__) && defined(__KERNEL_GPU__)
-		kernel_split_params.dummy_sd_flag = sd->flag;
-#endif
-		/* setup new shading point */
-		shader_setup_from_subsurface(kg, sd, &ss_isect.hits[0], &ray);
-
-		/* Probability densities for local frame axes. */
-		float pdf_N = pick_pdf_N * fabsf(dot(disk_N, sd->Ng));
-		float pdf_T = pick_pdf_T * fabsf(dot(disk_T, sd->Ng));
-		float pdf_B = pick_pdf_B * fabsf(dot(disk_B, sd->Ng));
-
-		/* Multiple importance sample between 3 axes, power heuristic
-		 * found to be slightly better than balance heuristic. pdf_N
-		 * in the MIS weight and denominator cancelled out. */
-		float w = pdf_N / (sqr(pdf_N) + sqr(pdf_T) + sqr(pdf_B));
-		w *= ss_isect.num_hits;
-
-		/* Real distance to sampled point. */
-		float r = len(sd->P - origP);
-
-		/* Evaluate profiles. */
-		eval = subsurface_scatter_eval(sd, sc, disk_r, r, all) * w;
-	}
-
-	/* optionally blur colors and bump mapping */
-	float3 N = sd->N;
-	subsurface_color_bump_blur(kg, sd, state, &eval, &N);
-
-	/* setup diffuse bsdf */
-	subsurface_scatter_setup_diffuse_bsdf(kg, sd, sc, eval, (ss_isect.num_hits > 0), N);
+	subsurface_scatter_setup_diffuse_bsdf(kg, sd, sc, weight, N);
 }
 
 /* Random walk subsurface scattering.