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, 1 deletions

diff --git a/intern/cycles/kernel/shaders/node_light_path.osl b/intern/cycles/kernel/shaders/node_light_path.osl
index 99a92c4f403..a021a40467d 100644
--- a/intern/cycles/kernel/shaders/node_light_path.osl
+++ b/intern/cycles/kernel/shaders/node_light_path.osl
@@ -27,7 +27,8 @@ shader node_light_path(
 	output float IsVolumeScatterRay = 0.0,
 	output float RayLength = 0.0,
 	output float RayDepth = 0.0,
-	output float TransparentDepth = 0.0)
+	output float TransparentDepth = 0.0,
+	output float TransmissionDepth = 0.0)
 {
 	IsCameraRay = raytype("camera");
 	IsShadowRay = raytype("shadow");
@@ -47,5 +48,9 @@ shader node_light_path(
 	int transparent_depth;
 	getattribute("path:transparent_depth", transparent_depth);
 	TransparentDepth = (float)transparent_depth;
+
+	int transmission_depth;
+	getattribute("path:transmission_depth", transmission_depth);
+	TransmissionDepth = (float)transmission_depth;
 }