Cycles: change AO bounces approximation to do more glossy and transmission.

Rather than treating all ray types equally, we now always render 1 glossy
bounce and unlimited transmission bounces. This makes it possible to get
good looking results with low AO bounces settings, making it useful to
speed up interior renders for example.

Reviewed By: brecht

Differential Revision: https://developer.blender.org/D2818

4 files changed, 31 insertions, 12 deletions

diff --git a/intern/cycles/kernel/kernel_path.h b/intern/cycles/kernel/kernel_path.h
index 3319e2c2435..bc8f8ec09f8 100644
--- a/intern/cycles/kernel/kernel_path.h
+++ b/intern/cycles/kernel/kernel_path.h
@@ -111,7 +111,7 @@ ccl_device void kernel_path_indirect(KernelGlobals *kg,
 		/* intersect scene */
 		Intersection isect;
 		uint visibility = path_state_ray_visibility(kg, state);
-		if(state->bounce > kernel_data.integrator.ao_bounces) {
+		if(path_state_ao_bounce(kg, state)) {
 			visibility = PATH_RAY_SHADOW;
 			ray->t = kernel_data.background.ao_distance;
 		}
@@ -294,7 +294,7 @@ ccl_device void kernel_path_indirect(KernelGlobals *kg,
 
 			break;
 		}
-		else if(state->bounce > kernel_data.integrator.ao_bounces) {
+		else if(path_state_ao_bounce(kg, state))  {
 			break;
 		}
 
@@ -473,13 +473,18 @@ ccl_device_inline void kernel_path_integrate(KernelGlobals *kg,
 			lcg_state = lcg_state_init(&state, 0x51633e2d);
 		}
 
-		if(state.bounce > kernel_data.integrator.ao_bounces) {
+		if(path_state_ao_bounce(kg, &state)) {
 			visibility = PATH_RAY_SHADOW;
 			ray.t = kernel_data.background.ao_distance;
 		}
 
 		bool hit = scene_intersect(kg, ray, visibility, &isect, &lcg_state, difl, extmax);
 #else
+		if(path_state_ao_bounce(kg, state)) {
+			visibility = PATH_RAY_SHADOW;
+			ray.t = kernel_data.background.ao_distance;
+		}
+
 		bool hit = scene_intersect(kg, ray, visibility, &isect, NULL, 0.0f, 0.0f);
 #endif  /* __HAIR__ */
 
@@ -620,7 +625,7 @@ ccl_device_inline void kernel_path_integrate(KernelGlobals *kg,
 
 			break;
 		}
-		else if(state.bounce > kernel_data.integrator.ao_bounces) {
+		else if(path_state_ao_bounce(kg, &state)) {
 			break;
 		}
 
diff --git a/intern/cycles/kernel/kernel_path_state.h b/intern/cycles/kernel/kernel_path_state.h
index af208ff37f1..bedcd655bc6 100644
--- a/intern/cycles/kernel/kernel_path_state.h
+++ b/intern/cycles/kernel/kernel_path_state.h
@@ -143,7 +143,7 @@ ccl_device_inline void path_state_next(KernelGlobals *kg, ccl_addr_space PathSta
 #endif
 }
 
-ccl_device_inline uint path_state_ray_visibility(KernelGlobals *kg, PathState *state)
+ccl_device_inline uint path_state_ray_visibility(KernelGlobals *kg, ccl_addr_space PathState *state)
 {
 	uint flag = state->flag & PATH_RAY_ALL_VISIBILITY;
 
@@ -214,5 +214,15 @@ ccl_device_inline void path_state_modify_bounce(ccl_addr_space PathState *state,
 		state->bounce -= 1;
 }
 
+ccl_device_inline bool path_state_ao_bounce(KernelGlobals *kg, ccl_addr_space PathState *state)
+{
+    if(state->bounce <= kernel_data.integrator.ao_bounces) {
+        return false;
+    }
+
+    int bounce = state->bounce - state->transmission_bounce - (state->glossy_bounce > 0);
+    return (bounce > kernel_data.integrator.ao_bounces);
+}
+
 CCL_NAMESPACE_END
 
diff --git a/intern/cycles/kernel/split/kernel_indirect_background.h b/intern/cycles/kernel/split/kernel_indirect_background.h
index 04d5769ef0d..2e9231caa3e 100644
--- a/intern/cycles/kernel/split/kernel_indirect_background.h
+++ b/intern/cycles/kernel/split/kernel_indirect_background.h
@@ -33,7 +33,7 @@ ccl_device void kernel_indirect_background(KernelGlobals *kg)
 		if(ray_index != QUEUE_EMPTY_SLOT) {
 			if(IS_STATE(ray_state, ray_index, RAY_ACTIVE)) {
 				ccl_global PathState *state = &kernel_split_state.path_state[ray_index];
-				if(state->bounce > kernel_data.integrator.ao_bounces) {
+				if(path_state_ao_bounce(kg, state)) {
 					kernel_split_path_end(kg, ray_index);
 				}
 			}
diff --git a/intern/cycles/kernel/split/kernel_scene_intersect.h b/intern/cycles/kernel/split/kernel_scene_intersect.h
index d0afd39ef29..99095f8fcbc 100644
--- a/intern/cycles/kernel/split/kernel_scene_intersect.h
+++ b/intern/cycles/kernel/split/kernel_scene_intersect.h
@@ -60,13 +60,13 @@ ccl_device void kernel_scene_intersect(KernelGlobals *kg)
 	}
 
 	Intersection isect;
-	PathState state = kernel_split_state.path_state[ray_index];
+	ccl_global PathState *state = &kernel_split_state.path_state[ray_index];
 	Ray ray = kernel_split_state.ray[ray_index];
 
 	/* intersect scene */
-	uint visibility = path_state_ray_visibility(kg, &state);
+	uint visibility = path_state_ray_visibility(kg, state);
 
-	if(state.bounce > kernel_data.integrator.ao_bounces) {
+	if(path_state_ao_bounce(kg, state)) {
 		visibility = PATH_RAY_SHADOW;
 		ray.t = kernel_data.background.ao_distance;
 	}
@@ -76,18 +76,22 @@ ccl_device void kernel_scene_intersect(KernelGlobals *kg)
 	uint lcg_state = 0;
 
 	if(kernel_data.bvh.have_curves) {
-		if((kernel_data.cam.resolution == 1) && (state.flag & PATH_RAY_CAMERA)) {
+		if((kernel_data.cam.resolution == 1) && (state->flag & PATH_RAY_CAMERA)) {
 			float3 pixdiff = ray.dD.dx + ray.dD.dy;
 			/*pixdiff = pixdiff - dot(pixdiff, ray.D)*ray.D;*/
 			difl = kernel_data.curve.minimum_width * len(pixdiff) * 0.5f;
 		}
 
 		extmax = kernel_data.curve.maximum_width;
-		lcg_state = lcg_state_init(&state, 0x51633e2d);
+		lcg_state = lcg_state_init_addrspace(state, 0x51633e2d);
 	}
 
 	bool hit = scene_intersect(kg, ray, visibility, &isect, &lcg_state, difl, extmax);
 #else
+	if(path_state_ao_bounce(kg, state)) {
+		visibility = PATH_RAY_SHADOW;
+		ray.t = kernel_data.background.ao_distance;
+	}
 	bool hit = scene_intersect(kg, ray, visibility, &isect, NULL, 0.0f, 0.0f);
 #endif
 	kernel_split_state.isect[ray_index] = isect;
@@ -95,7 +99,7 @@ ccl_device void kernel_scene_intersect(KernelGlobals *kg)
 #ifdef __KERNEL_DEBUG__
 	PathRadiance *L = &kernel_split_state.path_radiance[ray_index];
 
-	if(state.flag & PATH_RAY_CAMERA) {
+	if(state->flag & PATH_RAY_CAMERA) {
 		L->debug_data.num_bvh_traversed_nodes += isect.num_traversed_nodes;
 		L->debug_data.num_bvh_traversed_instances += isect.num_traversed_instances;
 		L->debug_data.num_bvh_intersections += isect.num_intersections;