/*
 * Copyright 2011-2015 Blender Foundation
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

CCL_NAMESPACE_BEGIN

/* This kernel takes care of scene_intersect function.
 *
 * This kernel changes the ray_state of RAY_REGENERATED rays to RAY_ACTIVE.
 * This kernel processes rays of ray state RAY_ACTIVE
 * This kernel determines the rays that have hit the background and changes
 * their ray state to RAY_HIT_BACKGROUND.
 */
ccl_device void kernel_scene_intersect(KernelGlobals *kg)
{
	/* Fetch use_queues_flag */
	char local_use_queues_flag = *kernel_split_params.use_queues_flag;
	ccl_barrier(CCL_LOCAL_MEM_FENCE);

	int ray_index = ccl_global_id(1) * ccl_global_size(0) + ccl_global_id(0);
	if(local_use_queues_flag) {
		ray_index = get_ray_index(kg, ray_index,
		                          QUEUE_ACTIVE_AND_REGENERATED_RAYS,
		                          kernel_split_state.queue_data,
		                          kernel_split_params.queue_size,
		                          0);

		if(ray_index == QUEUE_EMPTY_SLOT) {
			return;
		}
	}

	/* All regenerated rays become active here */
	if(IS_STATE(kernel_split_state.ray_state, ray_index, RAY_REGENERATED)) {
#ifdef __BRANCHED_PATH__
		if(kernel_split_state.branched_state[ray_index].waiting_on_shared_samples) {
			kernel_split_path_end(kg, ray_index);
		}
		else
#endif  /* __BRANCHED_PATH__ */
		{
			ASSIGN_RAY_STATE(kernel_split_state.ray_state, ray_index, RAY_ACTIVE);
		}
	}

	if(!IS_STATE(kernel_split_state.ray_state, ray_index, RAY_ACTIVE)) {
		return;
	}

#ifdef __KERNEL_DEBUG__
	DebugData *debug_data = &kernel_split_state.debug_data[ray_index];
#endif
	Intersection isect;
	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);

	if(state.bounce > kernel_data.integrator.ao_bounces) {
		visibility = PATH_RAY_SHADOW;
		ray.t = kernel_data.background.ao_distance;
	}

#ifdef __HAIR__
	float difl = 0.0f, extmax = 0.0f;
	uint lcg_state = 0;
	RNG rng = kernel_split_state.rng[ray_index];

	if(kernel_data.bvh.have_curves) {
		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(&rng, state.rng_offset, state.sample, 0x51633e2d);
	}

	bool hit = scene_intersect(kg, ray, visibility, &isect, &lcg_state, difl, extmax);
#else
	bool hit = scene_intersect(kg, ray, visibility, &isect, NULL, 0.0f, 0.0f);
#endif
	kernel_split_state.isect[ray_index] = isect;

#ifdef __KERNEL_DEBUG__
	if(state.flag & PATH_RAY_CAMERA) {
		debug_data->num_bvh_traversed_nodes += isect.num_traversed_nodes;
		debug_data->num_bvh_traversed_instances += isect.num_traversed_instances;
		debug_data->num_bvh_intersections += isect.num_intersections;
	}
	debug_data->num_ray_bounces++;
#endif

	if(!hit) {
		/* Change the state of rays that hit the background;
		 * These rays undergo special processing in the
		 * background_bufferUpdate kernel.
		 */
		ASSIGN_RAY_STATE(kernel_split_state.ray_state, ray_index, RAY_HIT_BACKGROUND);
	}
}

CCL_NAMESPACE_END