/*
 * 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 setting up ray for the next iteration of
 * path-iteration and accumulating radiance corresponding to AO and
 * direct-lighting
 *
 * Ray state of rays that are terminated in this kernel are changed
 * to RAY_UPDATE_BUFFER.
 *
 * Note on queues:
 * This kernel fetches rays from the queue QUEUE_ACTIVE_AND_REGENERATED_RAYS
 * and processes only the rays of state RAY_ACTIVE.
 * There are different points in this kernel where a ray may terminate and
 * reach RAY_UPDATE_BUFF state. These rays are enqueued into
 * QUEUE_HITBG_BUFF_UPDATE_TOREGEN_RAYS queue. These rays will still be present
 * in QUEUE_ACTIVE_AND_REGENERATED_RAYS queue, but since their ray-state has
 * been changed to RAY_UPDATE_BUFF, there is no problem.
 *
 * State of queues when this kernel is called:
 * At entry,
 *   - QUEUE_ACTIVE_AND_REGENERATED_RAYS will be filled with RAY_ACTIVE,
 *     RAY_REGENERATED, RAY_UPDATE_BUFFER rays.
 *   - QUEUE_HITBG_BUFF_UPDATE_TOREGEN_RAYS will be filled with
 *     RAY_TO_REGENERATE and RAY_UPDATE_BUFFER rays.
 * At exit,
 *   - QUEUE_ACTIVE_AND_REGENERATED_RAYS will be filled with RAY_ACTIVE,
 *     RAY_REGENERATED and more RAY_UPDATE_BUFFER rays.
 *   - QUEUE_HITBG_BUFF_UPDATE_TOREGEN_RAYS will be filled with
 *     RAY_TO_REGENERATE and more RAY_UPDATE_BUFFER rays.
 */

#ifdef __BRANCHED_PATH__
ccl_device_inline void kernel_split_branched_indirect_light_init(KernelGlobals *kg, int ray_index)
{
	kernel_split_branched_path_indirect_loop_init(kg, ray_index);

	ADD_RAY_FLAG(kernel_split_state.ray_state, ray_index, RAY_BRANCHED_LIGHT_INDIRECT);
}

ccl_device void kernel_split_branched_transparent_bounce(KernelGlobals *kg, int ray_index)
{
	ccl_global float3 *throughput = &kernel_split_state.throughput[ray_index];
	ShaderData *sd = kernel_split_sd(sd, ray_index);
	ccl_global PathState *state = &kernel_split_state.path_state[ray_index];
	ccl_global Ray *ray = &kernel_split_state.ray[ray_index];

#  ifdef __VOLUME__
	if(!(sd->flag & SD_HAS_ONLY_VOLUME)) {
#  endif
		/* continue in case of transparency */
		*throughput *= shader_bsdf_transparency(kg, sd);

		if(is_zero(*throughput)) {
			kernel_split_path_end(kg, ray_index);
			return;
		}

		/* Update Path State */
		path_state_next(kg, state, LABEL_TRANSPARENT);
#  ifdef __VOLUME__
	}
	else {
		if(!path_state_volume_next(kg, state)) {
			kernel_split_path_end(kg, ray_index);
			return;
		}
	}
#  endif

	ray->P = ray_offset(sd->P, -sd->Ng);
	ray->t -= sd->ray_length; /* clipping works through transparent */

#  ifdef __RAY_DIFFERENTIALS__
	ray->dP = sd->dP;
	ray->dD.dx = -sd->dI.dx;
	ray->dD.dy = -sd->dI.dy;
#  endif  /* __RAY_DIFFERENTIALS__ */

#  ifdef __VOLUME__
	/* enter/exit volume */
	kernel_volume_stack_enter_exit(kg, sd, state->volume_stack);
#  endif  /* __VOLUME__ */
}
#endif  /* __BRANCHED_PATH__ */

ccl_device void kernel_next_iteration_setup(KernelGlobals *kg,
                                            ccl_local_param unsigned int *local_queue_atomics)
{
	if(ccl_local_id(0) == 0 && ccl_local_id(1) == 0) {
		*local_queue_atomics = 0;
	}
	ccl_barrier(CCL_LOCAL_MEM_FENCE);

	if(ccl_global_id(0) == 0 && ccl_global_id(1) == 0) {
		/* If we are here, then it means that scene-intersect kernel
		* has already been executed atleast once. From the next time,
		* scene-intersect kernel may operate on queues to fetch ray index
		*/
		*kernel_split_params.use_queues_flag = 1;

		/* Mark queue indices of QUEUE_SHADOW_RAY_CAST_AO_RAYS and
		 * QUEUE_SHADOW_RAY_CAST_DL_RAYS queues that were made empty during the
		 * previous kernel.
		 */
		kernel_split_params.queue_index[QUEUE_SHADOW_RAY_CAST_AO_RAYS] = 0;
		kernel_split_params.queue_index[QUEUE_SHADOW_RAY_CAST_DL_RAYS] = 0;
	}

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

	ccl_global char *ray_state = kernel_split_state.ray_state;

#  ifdef __VOLUME__
	/* Reactivate only volume rays here, most surface work was skipped. */
	if(IS_STATE(ray_state, ray_index, RAY_HAS_ONLY_VOLUME)) {
		ASSIGN_RAY_STATE(ray_state, ray_index, RAY_ACTIVE);
	}
#  endif

	bool active = IS_STATE(ray_state, ray_index, RAY_ACTIVE);
	if(active) {
		ccl_global float3 *throughput = &kernel_split_state.throughput[ray_index];
		ccl_global Ray *ray = &kernel_split_state.ray[ray_index];
		ShaderData *sd = kernel_split_sd(sd, ray_index);
		ccl_global PathState *state = &kernel_split_state.path_state[ray_index];
		PathRadiance *L = &kernel_split_state.path_radiance[ray_index];

#ifdef __BRANCHED_PATH__
		if(!kernel_data.integrator.branched || IS_FLAG(ray_state, ray_index, RAY_BRANCHED_INDIRECT)) {
#endif
			/* Compute direct lighting and next bounce. */
			if(!kernel_path_surface_bounce(kg, sd, throughput, state, &L->state, ray)) {
				kernel_split_path_end(kg, ray_index);
			}
#ifdef __BRANCHED_PATH__
		}
		else if(sd->flag & SD_HAS_ONLY_VOLUME) {
			kernel_split_branched_transparent_bounce(kg, ray_index);
		}
		else {
			kernel_split_branched_indirect_light_init(kg, ray_index);

			if(kernel_split_branched_path_surface_indirect_light_iter(kg,
			                                                          ray_index,
			                                                          1.0f,
			                                                          kernel_split_sd(branched_state_sd, ray_index),
			                                                          true,
			                                                          true))
			{
				ASSIGN_RAY_STATE(ray_state, ray_index, RAY_REGENERATED);
			}
			else {
				kernel_split_branched_path_indirect_loop_end(kg, ray_index);
				kernel_split_branched_transparent_bounce(kg, ray_index);
			}
		}
#endif  /* __BRANCHED_PATH__ */
	}

	/* Enqueue RAY_UPDATE_BUFFER rays. */
	enqueue_ray_index_local(ray_index,
	                        QUEUE_HITBG_BUFF_UPDATE_TOREGEN_RAYS,
	                        IS_STATE(ray_state, ray_index, RAY_UPDATE_BUFFER) && active,
	                        kernel_split_params.queue_size,
	                        local_queue_atomics,
	                        kernel_split_state.queue_data,
	                        kernel_split_params.queue_index);

#ifdef __BRANCHED_PATH__
	/* iter loop */
	if(ccl_global_id(0) == 0 && ccl_global_id(1) == 0) {
		kernel_split_params.queue_index[QUEUE_LIGHT_INDIRECT_ITER] = 0;
	}

	ray_index = get_ray_index(kg, ccl_global_id(1) * ccl_global_size(0) + ccl_global_id(0),
	                          QUEUE_LIGHT_INDIRECT_ITER,
	                          kernel_split_state.queue_data,
	                          kernel_split_params.queue_size,
	                          1);

	if(IS_STATE(ray_state, ray_index, RAY_LIGHT_INDIRECT_NEXT_ITER)) {
		/* for render passes, sum and reset indirect light pass variables
		 * for the next samples */
		PathRadiance *L = &kernel_split_state.path_radiance[ray_index];

		path_radiance_sum_indirect(L);
		path_radiance_reset_indirect(L);

		if(kernel_split_branched_path_surface_indirect_light_iter(kg,
		                                                          ray_index,
		                                                          1.0f,
		                                                          kernel_split_sd(branched_state_sd, ray_index),
		                                                          true,
		                                                          true))
		{
			ASSIGN_RAY_STATE(ray_state, ray_index, RAY_REGENERATED);
		}
		else {
			kernel_split_branched_path_indirect_loop_end(kg, ray_index);
			kernel_split_branched_transparent_bounce(kg, ray_index);
		}
	}

#  ifdef __VOLUME__
	/* Enqueue RAY_VOLUME_INDIRECT_NEXT_ITER rays */
	ccl_barrier(CCL_LOCAL_MEM_FENCE);
	if(ccl_local_id(0) == 0 && ccl_local_id(1) == 0) {
		*local_queue_atomics = 0;
	}
	ccl_barrier(CCL_LOCAL_MEM_FENCE);

	ray_index = ccl_global_id(1) * ccl_global_size(0) + ccl_global_id(0);
	enqueue_ray_index_local(ray_index,
	                        QUEUE_VOLUME_INDIRECT_ITER,
	                        IS_STATE(kernel_split_state.ray_state, ray_index, RAY_VOLUME_INDIRECT_NEXT_ITER),
	                        kernel_split_params.queue_size,
	                        local_queue_atomics,
	                        kernel_split_state.queue_data,
	                        kernel_split_params.queue_index);

#  endif  /* __VOLUME__ */

#  ifdef __SUBSURFACE__
	/* Enqueue RAY_SUBSURFACE_INDIRECT_NEXT_ITER rays */
	ccl_barrier(CCL_LOCAL_MEM_FENCE);
	if(ccl_local_id(0) == 0 && ccl_local_id(1) == 0) {
		*local_queue_atomics = 0;
	}
	ccl_barrier(CCL_LOCAL_MEM_FENCE);

	ray_index = ccl_global_id(1) * ccl_global_size(0) + ccl_global_id(0);
	enqueue_ray_index_local(ray_index,
	                        QUEUE_SUBSURFACE_INDIRECT_ITER,
	                        IS_STATE(kernel_split_state.ray_state, ray_index, RAY_SUBSURFACE_INDIRECT_NEXT_ITER),
	                        kernel_split_params.queue_size,
	                        local_queue_atomics,
	                        kernel_split_state.queue_data,
	                        kernel_split_params.queue_index);
#  endif  /* __SUBSURFACE__ */
#endif  /* __BRANCHED_PATH__ */
}

CCL_NAMESPACE_END
