Cycles: Refactor how we pass bounce info to light path node.

This commit changes the way how we pass bounce information to the Light
Path node. Instead of manualy copying the bounces into ShaderData, we now
directly pass PathState. This reduces the arguments that we need to pass
around and also makes it easier to extend the feature.

This commit also exposes the Transmission Bounce Depth to the Light Path
node. It works similar to the Transparent Depth Output: Replace a
Transmission lightpath after X bounces with another shader, e.g a Diffuse
one. This can be used to avoid black surfaces, due to low amount of max
bounces.

Reviewed by Sergey and Brecht, thanks for some hlp with this.

I tested compilation and usage on CPU (SVM and OSL), CUDA, OpenCL Split
and Mega kernel. Hopefully this covers all devices. :)

1 files changed, 6 insertions, 4 deletions

diff --git a/intern/cycles/kernel/kernel_subsurface.h b/intern/cycles/kernel/kernel_subsurface.h
index 27a341aa37a..e5572be114a 100644
--- a/intern/cycles/kernel/kernel_subsurface.h
+++ b/intern/cycles/kernel/kernel_subsurface.h
@@ -181,6 +181,7 @@ ccl_device float3 subsurface_color_pow(float3 color, float exponent)
 
 ccl_device void subsurface_color_bump_blur(KernelGlobals *kg,
                                            ShaderData *sd,
+                                           PathState *state,
                                            int state_flag,
                                            float3 *eval,
                                            float3 *N)
@@ -194,7 +195,7 @@ ccl_device void subsurface_color_bump_blur(KernelGlobals *kg,
 
 	if(bump || texture_blur > 0.0f) {
 		/* average color and normal at incoming point */
-		shader_eval_surface(kg, sd, 0.0f, state_flag, SHADER_CONTEXT_SSS);
+		shader_eval_surface(kg, sd, state, 0.0f, state_flag, SHADER_CONTEXT_SSS);
 		float3 in_color = shader_bssrdf_sum(sd, (bump)? N: NULL, NULL);
 
 		/* we simply divide out the average color and multiply with the average
@@ -329,6 +330,7 @@ ccl_device void subsurface_scatter_multi_setup(KernelGlobals *kg,
                                                SubsurfaceIntersection* ss_isect,
                                                int hit,
                                                ShaderData *sd,
+                                               PathState *state,
                                                int state_flag,
                                                ShaderClosure *sc,
                                                bool all)
@@ -339,14 +341,14 @@ ccl_device void subsurface_scatter_multi_setup(KernelGlobals *kg,
 	/* Optionally blur colors and bump mapping. */
 	float3 weight = ss_isect->weight[hit];
 	float3 N = sd->N;
-	subsurface_color_bump_blur(kg, sd, state_flag, &weight, &N);
+	subsurface_color_bump_blur(kg, sd, state, state_flag, &weight, &N);
 
 	/* Setup diffuse BSDF. */
 	subsurface_scatter_setup_diffuse_bsdf(sd, 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_device void subsurface_scatter_step(KernelGlobals *kg, ShaderData *sd,  PathState *state,
 	int state_flag, ShaderClosure *sc, uint *lcg_state, float disk_u, float disk_v, bool all)
 {
 	float3 eval = make_float3(0.0f, 0.0f, 0.0f);
@@ -429,7 +431,7 @@ ccl_device void subsurface_scatter_step(KernelGlobals *kg, ShaderData *sd,
 
 	/* optionally blur colors and bump mapping */
 	float3 N = sd->N;
-	subsurface_color_bump_blur(kg, sd, state_flag, &eval, &N);
+	subsurface_color_bump_blur(kg, sd, state, state_flag, &eval, &N);
 
 	/* setup diffuse bsdf */
 	subsurface_scatter_setup_diffuse_bsdf(sd, eval, (ss_isect.num_hits > 0), N);