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, 12 insertions, 8 deletions

diff --git a/intern/cycles/kernel/osl/osl_shader.cpp b/intern/cycles/kernel/osl/osl_shader.cpp
index 2f234aa25ea..950786ab213 100644
--- a/intern/cycles/kernel/osl/osl_shader.cpp
+++ b/intern/cycles/kernel/osl/osl_shader.cpp
@@ -92,7 +92,7 @@ void OSLShader::thread_free(KernelGlobals *kg)
 
 /* Globals */
 
-static void shaderdata_to_shaderglobals(KernelGlobals *kg, ShaderData *sd,
+static void shaderdata_to_shaderglobals(KernelGlobals *kg, ShaderData *sd, PathState *state,
                                         int path_flag, OSLThreadData *tdata)
 {
 	OSL::ShaderGlobals *globals = &tdata->globals;
@@ -136,6 +136,7 @@ static void shaderdata_to_shaderglobals(KernelGlobals *kg, ShaderData *sd,
 
 	/* used by renderservices */
 	sd->osl_globals = kg;
+	sd->osl_path_state = state;
 }
 
 /* Surface */
@@ -317,11 +318,11 @@ static void flatten_surface_closure_tree(ShaderData *sd, int path_flag,
 	}
 }
 
-void OSLShader::eval_surface(KernelGlobals *kg, ShaderData *sd, int path_flag, ShaderContext ctx)
+void OSLShader::eval_surface(KernelGlobals *kg, ShaderData *sd, PathState *state, int path_flag, ShaderContext ctx)
 {
 	/* setup shader globals from shader data */
 	OSLThreadData *tdata = kg->osl_tdata;
-	shaderdata_to_shaderglobals(kg, sd, path_flag, tdata);
+	shaderdata_to_shaderglobals(kg, sd, state, path_flag, tdata);
 
 	/* execute shader for this point */
 	OSL::ShadingSystem *ss = (OSL::ShadingSystem*)kg->osl_ss;
@@ -377,11 +378,11 @@ static float3 flatten_background_closure_tree(const OSL::ClosureColor *closure)
 	return make_float3(0.0f, 0.0f, 0.0f);
 }
 
-float3 OSLShader::eval_background(KernelGlobals *kg, ShaderData *sd, int path_flag, ShaderContext ctx)
+float3 OSLShader::eval_background(KernelGlobals *kg, ShaderData *sd, PathState *state, int path_flag, ShaderContext ctx)
 {
 	/* setup shader globals from shader data */
 	OSLThreadData *tdata = kg->osl_tdata;
-	shaderdata_to_shaderglobals(kg, sd, path_flag, tdata);
+	shaderdata_to_shaderglobals(kg, sd, state, path_flag, tdata);
 
 	/* execute shader for this point */
 	OSL::ShadingSystem *ss = (OSL::ShadingSystem*)kg->osl_ss;
@@ -486,11 +487,11 @@ static void flatten_volume_closure_tree(ShaderData *sd,
 	}
 }
 
-void OSLShader::eval_volume(KernelGlobals *kg, ShaderData *sd, int path_flag, ShaderContext ctx)
+void OSLShader::eval_volume(KernelGlobals *kg, ShaderData *sd, PathState *state, int path_flag, ShaderContext ctx)
 {
 	/* setup shader globals from shader data */
 	OSLThreadData *tdata = kg->osl_tdata;
-	shaderdata_to_shaderglobals(kg, sd, path_flag, tdata);
+	shaderdata_to_shaderglobals(kg, sd, state, path_flag, tdata);
 
 	/* execute shader */
 	OSL::ShadingSystem *ss = (OSL::ShadingSystem*)kg->osl_ss;
@@ -512,7 +513,10 @@ void OSLShader::eval_displacement(KernelGlobals *kg, ShaderData *sd, ShaderConte
 {
 	/* setup shader globals from shader data */
 	OSLThreadData *tdata = kg->osl_tdata;
-	shaderdata_to_shaderglobals(kg, sd, 0, tdata);
+
+	PathState state = {0};
+
+	shaderdata_to_shaderglobals(kg, sd, &state, 0, tdata);
 
 	/* execute shader */
 	OSL::ShadingSystem *ss = (OSL::ShadingSystem*)kg->osl_ss;