/*
 * Copyright 2011-2013 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.
 */

/* This is a template BVH traversal function, where various features can be
 * enabled/disabled. This way we can compile optimized versions for each case
 * without new features slowing things down.
 *
 * BVH_INSTANCING: object instancing
 * BVH_HAIR: hair curve rendering
 * BVH_MOTION: motion blur rendering
 *
 */

#if BVH_FEATURE(BVH_HAIR)
#  define NODE_INTERSECT qbvh_node_intersect
#else
#  define NODE_INTERSECT qbvh_aligned_node_intersect
#endif

ccl_device bool BVH_FUNCTION_FULL_NAME(QBVH)(KernelGlobals *kg,
                                             const Ray *ray,
                                             Intersection *isect_array,
                                             const uint visibility,
                                             const uint max_hits,
                                             uint *num_hits)
{
	/* TODO(sergey):
	*  - Test if pushing distance on the stack helps.
	 * - Likely and unlikely for if() statements.
	 * - Test restrict attribute for pointers.
	 */

	/* Traversal stack in CUDA thread-local memory. */
	QBVHStackItem traversal_stack[BVH_QSTACK_SIZE];
	traversal_stack[0].addr = ENTRYPOINT_SENTINEL;

	/* Traversal variables in registers. */
	int stack_ptr = 0;
	int node_addr = kernel_data.bvh.root;

	/* Ray parameters in registers. */
	const float tmax = ray->t;
	float3 P = ray->P;
	float3 dir = bvh_clamp_direction(ray->D);
	float3 idir = bvh_inverse_direction(dir);
	int object = OBJECT_NONE;
	float isect_t = tmax;

#if BVH_FEATURE(BVH_MOTION)
	Transform ob_itfm;
#endif

	*num_hits = 0;
	isect_array->t = tmax;

#ifndef __KERNEL_SSE41__
	if(!isfinite(P.x)) {
		return false;
	}
#endif

#if BVH_FEATURE(BVH_INSTANCING)
	int num_hits_in_instance = 0;
#endif

	ssef tnear(0.0f), tfar(isect_t);
#if BVH_FEATURE(BVH_HAIR)
	sse3f dir4(ssef(dir.x), ssef(dir.y), ssef(dir.z));
#endif
	sse3f idir4(ssef(idir.x), ssef(idir.y), ssef(idir.z));

#ifdef __KERNEL_AVX2__
	float3 P_idir = P*idir;
	sse3f P_idir4(P_idir.x, P_idir.y, P_idir.z);
#endif
#if BVH_FEATURE(BVH_HAIR) || !defined(__KERNEL_AVX2__)
	sse3f org4(ssef(P.x), ssef(P.y), ssef(P.z));
#endif

	/* Offsets to select the side that becomes the lower or upper bound. */
	int near_x, near_y, near_z;
	int far_x, far_y, far_z;
	qbvh_near_far_idx_calc(idir,
	                       &near_x, &near_y, &near_z,
	                       &far_x, &far_y, &far_z);

	/* Traversal loop. */
	do {
		do {
			/* Traverse internal nodes. */
			while(node_addr >= 0 && node_addr != ENTRYPOINT_SENTINEL) {
				float4 inodes = kernel_tex_fetch(__bvh_nodes, node_addr+0);
				(void)inodes;

				if(false
#ifdef __VISIBILITY_FLAG__
				   || ((__float_as_uint(inodes.x) & visibility) == 0)
#endif
#if BVH_FEATURE(BVH_MOTION)
				   || UNLIKELY(ray->time < inodes.y)
				   || UNLIKELY(ray->time > inodes.z)
#endif
				) {
					/* Pop. */
					node_addr = traversal_stack[stack_ptr].addr;
					--stack_ptr;
					continue;
				}

				ssef dist;
				int child_mask = NODE_INTERSECT(kg,
				                                tnear,
				                                tfar,
#ifdef __KERNEL_AVX2__
				                                P_idir4,
#endif
#if BVH_FEATURE(BVH_HAIR) || !defined(__KERNEL_AVX2__)
				                                org4,
#endif
#if BVH_FEATURE(BVH_HAIR)
				                                dir4,
#endif
				                                idir4,
				                                near_x, near_y, near_z,
				                                far_x, far_y, far_z,
				                                node_addr,
				                                &dist);

				if(child_mask != 0) {
					float4 cnodes;
#if BVH_FEATURE(BVH_HAIR)
					if(__float_as_uint(inodes.x) & PATH_RAY_NODE_UNALIGNED) {
						cnodes = kernel_tex_fetch(__bvh_nodes, node_addr+13);
					}
					else
#endif
					{
						cnodes = kernel_tex_fetch(__bvh_nodes, node_addr+7);
					}

					/* One child is hit, continue with that child. */
					int r = __bscf(child_mask);
					if(child_mask == 0) {
						node_addr = __float_as_int(cnodes[r]);
						continue;
					}

					/* Two children are hit, push far child, and continue with
					 * closer child.
					 */
					int c0 = __float_as_int(cnodes[r]);
					float d0 = ((float*)&dist)[r];
					r = __bscf(child_mask);
					int c1 = __float_as_int(cnodes[r]);
					float d1 = ((float*)&dist)[r];
					if(child_mask == 0) {
						if(d1 < d0) {
							node_addr = c1;
							++stack_ptr;
							kernel_assert(stack_ptr < BVH_QSTACK_SIZE);
							traversal_stack[stack_ptr].addr = c0;
							traversal_stack[stack_ptr].dist = d0;
							continue;
						}
						else {
							node_addr = c0;
							++stack_ptr;
							kernel_assert(stack_ptr < BVH_QSTACK_SIZE);
							traversal_stack[stack_ptr].addr = c1;
							traversal_stack[stack_ptr].dist = d1;
							continue;
						}
					}

					/* Here starts the slow path for 3 or 4 hit children. We push
					 * all nodes onto the stack to sort them there.
					 */
					++stack_ptr;
					kernel_assert(stack_ptr < BVH_QSTACK_SIZE);
					traversal_stack[stack_ptr].addr = c1;
					traversal_stack[stack_ptr].dist = d1;
					++stack_ptr;
					kernel_assert(stack_ptr < BVH_QSTACK_SIZE);
					traversal_stack[stack_ptr].addr = c0;
					traversal_stack[stack_ptr].dist = d0;

					/* Three children are hit, push all onto stack and sort 3
					 * stack items, continue with closest child.
					 */
					r = __bscf(child_mask);
					int c2 = __float_as_int(cnodes[r]);
					float d2 = ((float*)&dist)[r];
					if(child_mask == 0) {
						++stack_ptr;
						kernel_assert(stack_ptr < BVH_QSTACK_SIZE);
						traversal_stack[stack_ptr].addr = c2;
						traversal_stack[stack_ptr].dist = d2;
						qbvh_stack_sort(&traversal_stack[stack_ptr],
						                &traversal_stack[stack_ptr - 1],
						                &traversal_stack[stack_ptr - 2]);
						node_addr = traversal_stack[stack_ptr].addr;
						--stack_ptr;
						continue;
					}

					/* Four children are hit, push all onto stack and sort 4
					 * stack items, continue with closest child.
					 */
					r = __bscf(child_mask);
					int c3 = __float_as_int(cnodes[r]);
					float d3 = ((float*)&dist)[r];
					++stack_ptr;
					kernel_assert(stack_ptr < BVH_QSTACK_SIZE);
					traversal_stack[stack_ptr].addr = c3;
					traversal_stack[stack_ptr].dist = d3;
					++stack_ptr;
					kernel_assert(stack_ptr < BVH_QSTACK_SIZE);
					traversal_stack[stack_ptr].addr = c2;
					traversal_stack[stack_ptr].dist = d2;
					qbvh_stack_sort(&traversal_stack[stack_ptr],
					                &traversal_stack[stack_ptr - 1],
					                &traversal_stack[stack_ptr - 2],
					                &traversal_stack[stack_ptr - 3]);
				}

				node_addr = traversal_stack[stack_ptr].addr;
				--stack_ptr;
			}

			/* If node is leaf, fetch triangle list. */
			if(node_addr < 0) {
				float4 leaf = kernel_tex_fetch(__bvh_leaf_nodes, (-node_addr-1));
#ifdef __VISIBILITY_FLAG__
				if((__float_as_uint(leaf.z) & visibility) == 0) {
					/* Pop. */
					node_addr = traversal_stack[stack_ptr].addr;
					--stack_ptr;
					continue;
				}
#endif

				int prim_addr = __float_as_int(leaf.x);

#if BVH_FEATURE(BVH_INSTANCING)
				if(prim_addr >= 0) {
#endif
					int prim_addr2 = __float_as_int(leaf.y);
					const uint type = __float_as_int(leaf.w);
					const uint p_type = type & PRIMITIVE_ALL;

					/* Pop. */
					node_addr = traversal_stack[stack_ptr].addr;
					--stack_ptr;

					/* Primitive intersection. */
					while(prim_addr < prim_addr2) {
						kernel_assert((kernel_tex_fetch(__prim_type, prim_addr) & PRIMITIVE_ALL) == p_type);
						bool hit;

						/* todo: specialized intersect functions which don't fill in
						 * isect unless needed and check SD_HAS_TRANSPARENT_SHADOW?
						 * might give a few % performance improvement */

						switch(p_type) {
							case PRIMITIVE_TRIANGLE: {
								hit = triangle_intersect(kg,
								                         isect_array,
								                         P,
								                         dir,
								                         visibility,
								                         object,
								                         prim_addr);
								break;
							}
#if BVH_FEATURE(BVH_MOTION)
							case PRIMITIVE_MOTION_TRIANGLE: {
								hit = motion_triangle_intersect(kg,
								                                isect_array,
								                                P,
								                                dir,
								                                ray->time,
								                                visibility,
								                                object,
								                                prim_addr);
								break;
							}
#endif
#if BVH_FEATURE(BVH_HAIR)
							case PRIMITIVE_CURVE:
							case PRIMITIVE_MOTION_CURVE: {
								const uint curve_type = kernel_tex_fetch(__prim_type, prim_addr);
								if(kernel_data.curve.curveflags & CURVE_KN_INTERPOLATE) {
									hit = cardinal_curve_intersect(kg,
									                               isect_array,
									                               P,
									                               dir,
									                               visibility,
									                               object,
									                               prim_addr,
									                               ray->time,
									                               curve_type,
									                               NULL,
									                               0, 0);
								}
								else {
									hit = curve_intersect(kg,
									                      isect_array,
									                      P,
									                      dir,
									                      visibility,
									                      object,
									                      prim_addr,
									                      ray->time,
									                      curve_type,
									                      NULL,
									                      0, 0);
								}
								break;
							}
#endif
							default: {
								hit = false;
								break;
							}
						}

						/* Shadow ray early termination. */
						if(hit) {
							/* detect if this surface has a shader with transparent shadows */

							/* todo: optimize so primitive visibility flag indicates if
							 * the primitive has a transparent shadow shader? */
							int prim = kernel_tex_fetch(__prim_index, isect_array->prim);
							int shader = 0;

#ifdef __HAIR__
							if(kernel_tex_fetch(__prim_type, isect_array->prim) & PRIMITIVE_ALL_TRIANGLE)
#endif
							{
								shader = kernel_tex_fetch(__tri_shader, prim);
							}
#ifdef __HAIR__
							else {
								float4 str = kernel_tex_fetch(__curves, prim);
								shader = __float_as_int(str.z);
							}
#endif
							int flag = kernel_tex_fetch(__shader_flag, (shader & SHADER_MASK)*SHADER_SIZE);

							/* if no transparent shadows, all light is blocked */
							if(!(flag & SD_HAS_TRANSPARENT_SHADOW)) {
								return true;
							}
							/* if maximum number of hits reached, block all light */
							else if(*num_hits == max_hits) {
								return true;
							}

							/* move on to next entry in intersections array */
							isect_array++;
							(*num_hits)++;
#if BVH_FEATURE(BVH_INSTANCING)
							num_hits_in_instance++;
#endif

							isect_array->t = isect_t;
						}

						prim_addr++;
					}
				}
#if BVH_FEATURE(BVH_INSTANCING)
				else {
					/* Instance push. */
					object = kernel_tex_fetch(__prim_object, -prim_addr-1);

#  if BVH_FEATURE(BVH_MOTION)
					isect_t = bvh_instance_motion_push(kg, object, ray, &P, &dir, &idir, isect_t, &ob_itfm);
#  else
					isect_t = bvh_instance_push(kg, object, ray, &P, &dir, &idir, isect_t);
#  endif

					num_hits_in_instance = 0;
					isect_array->t = isect_t;

					qbvh_near_far_idx_calc(idir,
					                       &near_x, &near_y, &near_z,
					                       &far_x, &far_y, &far_z);
					tfar = ssef(isect_t);
#  if BVH_FEATURE(BVH_HAIR)
					dir4 = sse3f(ssef(dir.x), ssef(dir.y), ssef(dir.z));
#  endif
					idir4 = sse3f(ssef(idir.x), ssef(idir.y), ssef(idir.z));
#  ifdef __KERNEL_AVX2__
					P_idir = P*idir;
					P_idir4 = sse3f(P_idir.x, P_idir.y, P_idir.z);
#  endif
#  if BVH_FEATURE(BVH_HAIR) || !defined(__KERNEL_AVX2__)
					org4 = sse3f(ssef(P.x), ssef(P.y), ssef(P.z));
#  endif

					++stack_ptr;
					kernel_assert(stack_ptr < BVH_QSTACK_SIZE);
					traversal_stack[stack_ptr].addr = ENTRYPOINT_SENTINEL;

					node_addr = kernel_tex_fetch(__object_node, object);

				}
			}
#endif  /* FEATURE(BVH_INSTANCING) */
		} while(node_addr != ENTRYPOINT_SENTINEL);

#if BVH_FEATURE(BVH_INSTANCING)
		if(stack_ptr >= 0) {
			kernel_assert(object != OBJECT_NONE);

			/* Instance pop. */
			if(num_hits_in_instance) {
				float t_fac;
#  if BVH_FEATURE(BVH_MOTION)
				bvh_instance_motion_pop_factor(kg, object, ray, &P, &dir, &idir, &t_fac, &ob_itfm);
#  else
				bvh_instance_pop_factor(kg, object, ray, &P, &dir, &idir, &t_fac);
#  endif
				/* Scale isect->t to adjust for instancing. */
				for(int i = 0; i < num_hits_in_instance; i++) {
					(isect_array-i-1)->t *= t_fac;
				}
			}
			else {
#  if BVH_FEATURE(BVH_MOTION)
				bvh_instance_motion_pop(kg, object, ray, &P, &dir, &idir, FLT_MAX, &ob_itfm);
#  else
				bvh_instance_pop(kg, object, ray, &P, &dir, &idir, FLT_MAX);
#  endif
			}

			isect_t = tmax;
			isect_array->t = isect_t;

			qbvh_near_far_idx_calc(idir,
			                       &near_x, &near_y, &near_z,
			                       &far_x, &far_y, &far_z);
			tfar = ssef(isect_t);
#  if BVH_FEATURE(BVH_HAIR)
			dir4 = sse3f(ssef(dir.x), ssef(dir.y), ssef(dir.z));
#  endif
			idir4 = sse3f(ssef(idir.x), ssef(idir.y), ssef(idir.z));
#  ifdef __KERNEL_AVX2__
			P_idir = P*idir;
			P_idir4 = sse3f(P_idir.x, P_idir.y, P_idir.z);
#  endif
#  if BVH_FEATURE(BVH_HAIR) || !defined(__KERNEL_AVX2__)
			org4 = sse3f(ssef(P.x), ssef(P.y), ssef(P.z));
#  endif

			object = OBJECT_NONE;
			node_addr = traversal_stack[stack_ptr].addr;
			--stack_ptr;
		}
#endif  /* FEATURE(BVH_INSTANCING) */
	} while(node_addr != ENTRYPOINT_SENTINEL);

	return false;
}

#undef NODE_INTERSECT