Cycles: Add debug pass showing average number of ray bounces per pixel

Quite straightforward implementation, but still needs some work for the split
kernel. Includes both regular and split kernel implementation for that.

The pass is not exposed to the interface yet because it's currently not really
easy to have same pass listed in the menu multiple times.

intern/cycles/blender/blender_session.cpp

@@ -271,6 +271,8 @@ static PassType get_pass_type(BL::RenderPass b_pass)
 		{
 			if(b_pass.debug_type() == BL::RenderPass::debug_type_BVH_TRAVERSAL_STEPS)
 				return PASS_BVH_TRAVERSAL_STEPS;
+			if(b_pass.debug_type() == BL::RenderPass::debug_type_RAY_BOUNCES)
+				return PASS_RAY_BOUNCES;
 			break;
 		}
 #endif
@@ -439,6 +441,7 @@ void BlenderSession::render()
 		Pass::add(PASS_COMBINED, passes);
 #ifdef WITH_CYCLES_DEBUG
 		Pass::add(PASS_BVH_TRAVERSAL_STEPS, passes);
+		/* Pass::add(PASS_RAY_BOUNCES, passes); */
 #endif
 
 		if(session_params.device.advanced_shading) {

intern/cycles/kernel/kernel_debug.h

@@ -19,6 +19,7 @@ CCL_NAMESPACE_BEGIN
 ccl_device_inline void debug_data_init(DebugData *debug_data)
 {
 	debug_data->num_bvh_traversal_steps = 0;
+	debug_data->num_ray_bounces = 0;
 }
 
 ccl_device_inline void kernel_write_debug_passes(KernelGlobals *kg,
@@ -33,6 +34,11 @@ ccl_device_inline void kernel_write_debug_passes(KernelGlobals *kg,
 		                        sample,
 		                        debug_data->num_bvh_traversal_steps);
 	}
+	if(flag & PASS_RAY_BOUNCES) {
+		kernel_write_pass_float(buffer + kernel_data.film.pass_ray_bounces,
+		                        sample,
+		                        debug_data->num_ray_bounces);
+	}
 }
 
 CCL_NAMESPACE_END

intern/cycles/kernel/kernel_path.h

@@ -477,6 +477,7 @@ ccl_device float4 kernel_path_integrate(KernelGlobals *kg, RNG *rng, int sample,
 		if(state.flag & PATH_RAY_CAMERA) {
 			debug_data.num_bvh_traversal_steps += isect.num_traversal_steps;
 		}
+		debug_data.num_ray_bounces++;
 #endif
 
 #ifdef __LAMP_MIS__
@@ -878,6 +879,7 @@ ccl_device float4 kernel_branched_path_integrate(KernelGlobals *kg, RNG *rng, in
 		if(state.flag & PATH_RAY_CAMERA) {
 			debug_data.num_bvh_traversal_steps += isect.num_traversal_steps;
 		}
+		debug_data.num_ray_bounces++;
 #endif
 
 #ifdef __VOLUME__

intern/cycles/kernel/kernel_types.h

@@ -337,6 +337,7 @@ typedef enum PassType {
 	PASS_LIGHT = (1 << 25), /* no real pass, used to force use_light_pass */
 #ifdef __KERNEL_DEBUG__
 	PASS_BVH_TRAVERSAL_STEPS = (1 << 26),
+	PASS_RAY_BOUNCES = (1 << 27),
 #endif
 } PassType;
 
@@ -848,7 +849,8 @@ typedef struct KernelFilm {
 
 #ifdef __KERNEL_DEBUG__
 	int pass_bvh_traversal_steps;
-	int pass_pad3, pass_pad4, pass_pad5;
+	int pass_ray_bounces;
+	int pass_pad3, pass_pad4;
 #endif
 } KernelFilm;
 
@@ -987,6 +989,7 @@ typedef ccl_addr_space struct DebugData {
 	// Total number of BVH node traversal steps and primitives intersections
 	// for the camera rays.
 	int num_bvh_traversal_steps;
+	int num_ray_bounces;
 } DebugData;
 #endif
 

intern/cycles/kernel/split/kernel_scene_intersect.h

@@ -124,6 +124,7 @@ ccl_device void kernel_scene_intersect(
 	if(state.flag & PATH_RAY_CAMERA) {
 		debug_data->num_bvh_traversal_steps += isect->num_traversal_steps;
 	}
+	debug_data->num_ray_bounces++;
 #endif
 
 	if(!hit) {

intern/cycles/render/buffers.cpp

@@ -197,6 +197,12 @@ bool RenderBuffers::get_pass_rect(PassType type, float exposure, int sample, int
 					pixels[0] = f;
 				}
 			}
+			else if(type == PASS_RAY_BOUNCES) {
+				for(int i = 0; i < size; i++, in += pass_stride, pixels++) {
+					float f = *in;
+					pixels[0] = f;
+				}
+			}
 #endif
 			else {
 				for(int i = 0; i < size; i++, in += pass_stride, pixels++) {

intern/cycles/render/film.cpp

@@ -151,6 +151,10 @@ void Pass::add(PassType type, vector<Pass>& passes)
 			pass.components = 1;
 			pass.exposure = false;
 			break;
+		case PASS_RAY_BOUNCES:
+			pass.components = 1;
+			pass.exposure = false;
+			break;
 #endif
 	}
 
@@ -399,6 +403,9 @@ void Film::device_update(Device *device, DeviceScene *dscene, Scene *scene)
 			case PASS_BVH_TRAVERSAL_STEPS:
 				kfilm->pass_bvh_traversal_steps = kfilm->pass_stride;
 				break;
+			case PASS_RAY_BOUNCES:
+				kfilm->pass_ray_bounces = kfilm->pass_stride;
+				break;
 #endif
 
 			case PASS_NONE: