/*
 * Adapted from code Copyright 2009-2010 NVIDIA Corporation,
 * and code copyright 2009-2012 Intel Corporation
 *
 * Modifications Copyright 2011-2014, 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
 *
 */

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

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

	/* Traversal variables in registers. */
	int stackPtr = 0;
	int nodeAddr = 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_tfm;
#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(tmax);
	sse3f idir4(ssef(idir.x), ssef(idir.y), ssef(idir.z));

#ifdef __KERNEL_AVX2__
	float3 P_idir = P*idir;
	sse3f P_idir4 = sse3f(P_idir.x, P_idir.y, P_idir.z);
#else
	sse3f org = sse3f(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;

	if(idir.x >= 0.0f) { near_x = 0; far_x = 1; } else { near_x = 1; far_x = 0; }
	if(idir.y >= 0.0f) { near_y = 2; far_y = 3; } else { near_y = 3; far_y = 2; }
	if(idir.z >= 0.0f) { near_z = 4; far_z = 5; } else { near_z = 5; far_z = 4; }

	IsectPrecalc isect_precalc;
	triangle_intersect_precalc(dir, &isect_precalc);

	/* Traversal loop. */
	do {
		do {
			/* Traverse internal nodes. */
			while(nodeAddr >= 0 && nodeAddr != ENTRYPOINT_SENTINEL) {
				ssef dist;
				int traverseChild = qbvh_node_intersect(kg,
				                                        tnear,
				                                        tfar,
#ifdef __KERNEL_AVX2__
				                                        P_idir4,
#else
				                                        org,
#endif
				                                        idir4,
				                                        near_x, near_y, near_z,
				                                        far_x, far_y, far_z,
				                                        nodeAddr,
				                                        &dist);

				if(traverseChild != 0) {
					float4 cnodes = kernel_tex_fetch(__bvh_nodes, nodeAddr*BVH_QNODE_SIZE+6);

					/* One child is hit, continue with that child. */
					int r = __bscf(traverseChild);
					if(traverseChild == 0) {
						nodeAddr = __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(traverseChild);
					int c1 = __float_as_int(cnodes[r]);
					float d1 = ((float*)&dist)[r];
					if(traverseChild == 0) {
						if(d1 < d0) {
							nodeAddr = c1;
							++stackPtr;
							kernel_assert(stackPtr < BVH_QSTACK_SIZE);
							traversalStack[stackPtr].addr = c0;
							traversalStack[stackPtr].dist = d0;
							continue;
						}
						else {
							nodeAddr = c0;
							++stackPtr;
							kernel_assert(stackPtr < BVH_QSTACK_SIZE);
							traversalStack[stackPtr].addr = c1;
							traversalStack[stackPtr].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.
					 */
					++stackPtr;
					kernel_assert(stackPtr < BVH_QSTACK_SIZE);
					traversalStack[stackPtr].addr = c1;
					traversalStack[stackPtr].dist = d1;
					++stackPtr;
					kernel_assert(stackPtr < BVH_QSTACK_SIZE);
					traversalStack[stackPtr].addr = c0;
					traversalStack[stackPtr].dist = d0;

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

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

				nodeAddr = traversalStack[stackPtr].addr;
				--stackPtr;
			}

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

				int primAddr = __float_as_int(leaf.x);

#if BVH_FEATURE(BVH_INSTANCING)
				if(primAddr >= 0) {
#endif
					int primAddr2 = __float_as_int(leaf.y);
					const uint type = __float_as_int(leaf.w);
					const uint p_type = type & PRIMITIVE_ALL;

					/* Pop. */
					nodeAddr = traversalStack[stackPtr].addr;
					--stackPtr;

					/* Primitive intersection. */
					while(primAddr < primAddr2) {
						kernel_assert(kernel_tex_fetch(__prim_type, primAddr) == 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_precalc, isect_array, P, PATH_RAY_SHADOW, object, primAddr);
								break;
							}
#if BVH_FEATURE(BVH_MOTION)
							case PRIMITIVE_MOTION_TRIANGLE: {
								hit = motion_triangle_intersect(kg, isect_array, P, dir, ray->time, PATH_RAY_SHADOW, object, primAddr);
								break;
							}
#endif
#if BVH_FEATURE(BVH_HAIR)
							case PRIMITIVE_CURVE:
							case PRIMITIVE_MOTION_CURVE: {
								if(kernel_data.curve.curveflags & CURVE_KN_INTERPOLATE) 
									hit = bvh_cardinal_curve_intersect(kg, isect_array, P, dir, PATH_RAY_SHADOW, object, primAddr, ray->time, type, NULL, 0, 0);
								else
									hit = bvh_curve_intersect(kg, isect_array, P, dir, PATH_RAY_SHADOW, object, primAddr, ray->time, 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)*2);

							/* 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;
						}

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

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

					num_hits_in_instance = 0;
					isect_array->t = isect_t;

					if(idir.x >= 0.0f) { near_x = 0; far_x = 1; } else { near_x = 1; far_x = 0; }
					if(idir.y >= 0.0f) { near_y = 2; far_y = 3; } else { near_y = 3; far_y = 2; }
					if(idir.z >= 0.0f) { near_z = 4; far_z = 5; } else { near_z = 5; far_z = 4; }
					tfar = ssef(isect_t);
					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);
#else
					org = sse3f(ssef(P.x), ssef(P.y), ssef(P.z));
#endif
					triangle_intersect_precalc(dir, &isect_precalc);

					++stackPtr;
					kernel_assert(stackPtr < BVH_QSTACK_SIZE);
					traversalStack[stackPtr].addr = ENTRYPOINT_SENTINEL;

					nodeAddr = kernel_tex_fetch(__object_node, object);

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

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

			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_tfm);
#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 {
				float ignore_t = FLT_MAX;

#if BVH_FEATURE(BVH_MOTION)
				bvh_instance_motion_pop(kg, object, ray, &P, &dir, &idir, &ignore_t, &ob_tfm);
#else
				bvh_instance_pop(kg, object, ray, &P, &dir, &idir, &ignore_t);
#endif
			}

			isect_t = tmax;
			isect_array->t = isect_t;

			if(idir.x >= 0.0f) { near_x = 0; far_x = 1; } else { near_x = 1; far_x = 0; }
			if(idir.y >= 0.0f) { near_y = 2; far_y = 3; } else { near_y = 3; far_y = 2; }
			if(idir.z >= 0.0f) { near_z = 4; far_z = 5; } else { near_z = 5; far_z = 4; }
			tfar = ssef(tmax);
			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);
#else
			org = sse3f(ssef(P.x), ssef(P.y), ssef(P.z));
#endif
			triangle_intersect_precalc(dir, &isect_precalc);

			object = OBJECT_NONE;
			nodeAddr = traversalStack[stackPtr].addr;
			--stackPtr;
		}
#endif  /* FEATURE(BVH_INSTANCING) */
	} while(nodeAddr != ENTRYPOINT_SENTINEL);

	return false;
}