Cycles: Subsurface Scattering

New features:

* Bump mapping now works with SSS
* Texture Blur factor for SSS, see the documentation for details:
http://wiki.blender.org/index.php/Doc:2.6/Manual/Render/Cycles/Nodes/Shaders#Subsurface_Scattering

Work in progress for feedback:

Initial implementation of the "BSSRDF Importance Sampling" paper, which uses
a different importance sampling method. It gives better quality results in
many ways, with the availability of both Cubic and Gaussian falloff functions,
but also tends to be more noisy when using the progressive integrator and does
not give great results with some geometry. It works quite well for the
non-progressive integrator and is often less noisy there.

This code may still change a lot, so unless you're testing it may be best to
stick to the Compatible falloff function.

Skin test render and file that takes advantage of the gaussian falloff:
http://www.pasteall.org/pic/show.php?id=57661
http://www.pasteall.org/pic/show.php?id=57662
http://www.pasteall.org/blend/23501

2 files changed, 23 insertions, 11 deletions

diff --git a/intern/cycles/kernel/svm/svm_closure.h b/intern/cycles/kernel/svm/svm_closure.h
index 847195134e8..bd4a2d781eb 100644
--- a/intern/cycles/kernel/svm/svm_closure.h
+++ b/intern/cycles/kernel/svm/svm_closure.h
@@ -340,28 +340,36 @@ __device void svm_node_closure_bsdf(KernelGlobals *kg, ShaderData *sd, float *st
 			break;
 		}
 #ifdef __SUBSURFACE__
-		case CLOSURE_BSSRDF_ID: {
+		case CLOSURE_BSSRDF_COMPATIBLE_ID:
+		case CLOSURE_BSSRDF_CUBIC_ID:
+		case CLOSURE_BSSRDF_GAUSSIAN_ID: {
 			ShaderClosure *sc = &sd->closure[sd->num_closure];
 			float3 weight = sc->weight * mix_weight;
 			float sample_weight = fabsf(average(weight));
+			
+			/* disable in case of diffuse ancestor, can't see it well then and
+			 * adds considerably noise due to probabilities of continuing path
+			 * getting lower and lower */
+			if(type != CLOSURE_BSSRDF_COMPATIBLE_ID && (path_flag & PATH_RAY_DIFFUSE_ANCESTOR))
+				param1 = 0.0f;
 
 			if(sample_weight > 1e-5f && sd->num_closure+2 < MAX_CLOSURE) {
 				/* radius * scale */
 				float3 radius = stack_load_float3(stack, data_node.w)*param1;
-				/* index of refraction */
-				float eta = fmaxf(param2, 1.0f + 1e-5f);
+				/* texture color blur */
+				float texture_blur = param2;
 
 				/* create one closure per color channel */
 				if(fabsf(weight.x) > 0.0f) {
 					sc->weight = make_float3(weight.x, 0.0f, 0.0f);
 					sc->sample_weight = sample_weight;
 					sc->data0 = radius.x;
-					sc->data1 = eta;
+					sc->data1 = texture_blur;
 #ifdef __OSL__
 					sc->prim = NULL;
 #endif
 					sc->N = N;
-					sd->flag |= bssrdf_setup(sc);
+					sd->flag |= bssrdf_setup(sc, (ClosureType)type);
 
 					sd->num_closure++;
 					sc++;
@@ -371,12 +379,12 @@ __device void svm_node_closure_bsdf(KernelGlobals *kg, ShaderData *sd, float *st
 					sc->weight = make_float3(0.0f, weight.y, 0.0f);
 					sc->sample_weight = sample_weight;
 					sc->data0 = radius.y;
-					sc->data1 = eta;
+					sc->data1 = texture_blur;
 #ifdef __OSL__
 					sc->prim = NULL;
 #endif
 					sc->N = N;
-					sd->flag |= bssrdf_setup(sc);
+					sd->flag |= bssrdf_setup(sc, (ClosureType)type);
 
 					sd->num_closure++;
 					sc++;
@@ -386,12 +394,12 @@ __device void svm_node_closure_bsdf(KernelGlobals *kg, ShaderData *sd, float *st
 					sc->weight = make_float3(0.0f, 0.0f, weight.z);
 					sc->sample_weight = sample_weight;
 					sc->data0 = radius.z;
-					sc->data1 = eta;
+					sc->data1 = texture_blur;
 #ifdef __OSL__
 					sc->prim = NULL;
 #endif
 					sc->N = N;
-					sd->flag |= bssrdf_setup(sc);
+					sd->flag |= bssrdf_setup(sc, (ClosureType)type);
 
 					sd->num_closure++;
 					sc++;
diff --git a/intern/cycles/kernel/svm/svm_types.h b/intern/cycles/kernel/svm/svm_types.h
index 939decf80a9..37ed5ead49f 100644
--- a/intern/cycles/kernel/svm/svm_types.h
+++ b/intern/cycles/kernel/svm/svm_types.h
@@ -369,8 +369,12 @@ typedef enum ClosureType {
 	CLOSURE_BSDF_BSSRDF_ID,
 	CLOSURE_BSDF_TRANSPARENT_ID,
 
+	/* BSSRDF */
+	CLOSURE_BSSRDF_COMPATIBLE_ID,
+	CLOSURE_BSSRDF_CUBIC_ID,
+	CLOSURE_BSSRDF_GAUSSIAN_ID,
+
 	/* Other */
-	CLOSURE_BSSRDF_ID,
 	CLOSURE_EMISSION_ID,
 	CLOSURE_DEBUG_ID,
 	CLOSURE_BACKGROUND_ID,
@@ -391,7 +395,7 @@ typedef enum ClosureType {
 #define CLOSURE_IS_BSDF_GLOSSY(type) (type >= CLOSURE_BSDF_GLOSSY_ID && type <= CLOSURE_BSDF_GLOSSY_TOON_ID)
 #define CLOSURE_IS_BSDF_TRANSMISSION(type) (type >= CLOSURE_BSDF_TRANSMISSION_ID && type <= CLOSURE_BSDF_SHARP_GLASS_ID)
 #define CLOSURE_IS_BSDF_BSSRDF(type) (type == CLOSURE_BSDF_BSSRDF_ID)
-#define CLOSURE_IS_BSSRDF(type) (type == CLOSURE_BSSRDF_ID)
+#define CLOSURE_IS_BSSRDF(type) (type >= CLOSURE_BSSRDF_COMPATIBLE_ID && type <= CLOSURE_BSSRDF_GAUSSIAN_ID)
 #define CLOSURE_IS_VOLUME(type) (type >= CLOSURE_VOLUME_ID && type <= CLOSURE_VOLUME_ISOTROPIC_ID)
 #define CLOSURE_IS_EMISSION(type) (type == CLOSURE_EMISSION_ID)
 #define CLOSURE_IS_HOLDOUT(type) (type == CLOSURE_HOLDOUT_ID)