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

#ifdef __QBVH__
#  include "qbvh_traversal.h"
#endif

#if BVH_FEATURE(BVH_HAIR)
#  define NODE_INTERSECT bvh_node_intersect
#  define NODE_INTERSECT_ROBUST bvh_node_intersect_robust
#else
#  define NODE_INTERSECT bvh_aligned_node_intersect
#  define NODE_INTERSECT_ROBUST bvh_aligned_node_intersect_robust
#endif

/* 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_HAIR_MINIMUM_WIDTH: hair curve rendering with minimum width
 * BVH_MOTION: motion blur rendering
 *
 */

ccl_device_noinline bool BVH_FUNCTION_FULL_NAME(BVH)(KernelGlobals *kg,
                                                     const Ray *ray,
                                                     Intersection *isect,
                                                     const uint visibility
#if BVH_FEATURE(BVH_HAIR_MINIMUM_WIDTH)
                                                     , uint *lcg_state,
                                                     float difl,
                                                     float extmax
#endif
                                                     )
{
	/* todo:
	 * - test if pushing distance on the stack helps (for non shadow rays)
	 * - separate version for shadow rays
	 * - likely and unlikely for if() statements
	 * - test restrict attribute for pointers
	 */

	/* traversal stack in CUDA thread-local memory */
	int traversal_stack[BVH_STACK_SIZE];
	traversal_stack[0] = ENTRYPOINT_SENTINEL;

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

	/* ray parameters in registers */
	float3 P = ray->P;
	float3 dir = bvh_clamp_direction(ray->D);
	float3 idir = bvh_inverse_direction(dir);
	int object = OBJECT_NONE;

#if BVH_FEATURE(BVH_MOTION)
	Transform ob_itfm;
#endif

	isect->t = ray->t;
	isect->u = 0.0f;
	isect->v = 0.0f;
	isect->prim = PRIM_NONE;
	isect->object = OBJECT_NONE;

	BVH_DEBUG_INIT();

#if defined(__KERNEL_SSE2__)
	const shuffle_swap_t shuf_identity = shuffle_swap_identity();
	const shuffle_swap_t shuf_swap = shuffle_swap_swap();

	const ssef pn = cast(ssei(0, 0, 0x80000000, 0x80000000));
	ssef Psplat[3], idirsplat[3];
#  if BVH_FEATURE(BVH_HAIR)
	ssef tnear(0.0f), tfar(isect->t);
#  endif
	shuffle_swap_t shufflexyz[3];

	Psplat[0] = ssef(P.x);
	Psplat[1] = ssef(P.y);
	Psplat[2] = ssef(P.z);

	ssef tsplat(0.0f, 0.0f, -isect->t, -isect->t);

	gen_idirsplat_swap(pn, shuf_identity, shuf_swap, idir, idirsplat, shufflexyz);
#endif

	IsectPrecalc isect_precalc;
	triangle_intersect_precalc(dir, &isect_precalc);

	/* traversal loop */
	do {
		do {
			/* traverse internal nodes */
			while(node_addr >= 0 && node_addr != ENTRYPOINT_SENTINEL) {
				int node_addr_child1, traverse_mask;
				float dist[2];
				float4 cnodes = kernel_tex_fetch(__bvh_nodes, node_addr+0);

#if !defined(__KERNEL_SSE2__)
#  if BVH_FEATURE(BVH_HAIR_MINIMUM_WIDTH)
				if(difl != 0.0f) {
					traverse_mask = NODE_INTERSECT_ROBUST(kg,
					                                      P,
#    if BVH_FEATURE(BVH_HAIR)
					                                      dir,
#    endif
					                                      idir,
					                                      isect->t,
					                                      difl,
					                                      extmax,
					                                      node_addr,
					                                      visibility,
					                                      dist);
				}
				else
#  endif
				{
					traverse_mask = NODE_INTERSECT(kg,
					                               P,
#    if BVH_FEATURE(BVH_HAIR)
					                               dir,
#    endif
					                               idir,
					                               isect->t,
					                               node_addr,
					                               visibility,
					                               dist);
				}
#else // __KERNEL_SSE2__
#  if BVH_FEATURE(BVH_HAIR_MINIMUM_WIDTH)
				if(difl != 0.0f) {
					traverse_mask = NODE_INTERSECT_ROBUST(kg,
					                                      P,
					                                      dir,
#    if BVH_FEATURE(BVH_HAIR)
					                                      tnear,
					                                      tfar,
#    endif
					                                      tsplat,
					                                      Psplat,
					                                      idirsplat,
					                                      shufflexyz,
					                                      difl,
					                                      extmax,
					                                      node_addr,
					                                      visibility,
					                                      dist);
				}
				else
#  endif
				{
					traverse_mask = NODE_INTERSECT(kg,
					                               P,
					                               dir,
#    if BVH_FEATURE(BVH_HAIR)
					                               tnear,
					                               tfar,
#    endif
					                               tsplat,
					                               Psplat,
					                               idirsplat,
					                               shufflexyz,
					                               node_addr,
					                               visibility,
					                               dist);
				}
#endif // __KERNEL_SSE2__

				node_addr = __float_as_int(cnodes.z);
				node_addr_child1 = __float_as_int(cnodes.w);

				if(traverse_mask == 3) {
					/* Both children were intersected, push the farther one. */
					bool is_closest_child1 = (dist[1] < dist[0]);
					if(is_closest_child1) {
						int tmp = node_addr;
						node_addr = node_addr_child1;
						node_addr_child1 = tmp;
					}

					++stack_ptr;
					kernel_assert(stack_ptr < BVH_STACK_SIZE);
					traversal_stack[stack_ptr] = node_addr_child1;
				}
				else {
					/* One child was intersected. */
					if(traverse_mask == 2) {
						node_addr = node_addr_child1;
					}
					else if(traverse_mask == 0) {
						/* Neither child was intersected. */
						node_addr = traversal_stack[stack_ptr];
						--stack_ptr;
					}
				}
				BVH_DEBUG_NEXT_STEP();
			}

			/* if node is leaf, fetch triangle list */
			if(node_addr < 0) {
				float4 leaf = kernel_tex_fetch(__bvh_leaf_nodes, (-node_addr-1));
				int prim_addr = __float_as_int(leaf.x);

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

					/* pop */
					node_addr = traversal_stack[stack_ptr];
					--stack_ptr;

					/* primitive intersection */
					switch(type & PRIMITIVE_ALL) {
						case PRIMITIVE_TRIANGLE: {
							for(; prim_addr < prim_addr2; prim_addr++) {
								BVH_DEBUG_NEXT_STEP();
								kernel_assert(kernel_tex_fetch(__prim_type, prim_addr) == type);
								if(triangle_intersect(kg,
								                      &isect_precalc,
								                      isect,
								                      P,
								                      visibility,
								                      object,
								                      prim_addr))
								{
									/* shadow ray early termination */
#if defined(__KERNEL_SSE2__)
									if(visibility == PATH_RAY_SHADOW_OPAQUE)
										return true;
									tsplat = ssef(0.0f, 0.0f, -isect->t, -isect->t);
#  if BVH_FEATURE(BVH_HAIR)
									tfar = ssef(isect->t);
#  endif
#else
									if(visibility == PATH_RAY_SHADOW_OPAQUE)
										return true;
#endif
								}
							}
							break;
						}
#if BVH_FEATURE(BVH_MOTION)
						case PRIMITIVE_MOTION_TRIANGLE: {
							for(; prim_addr < prim_addr2; prim_addr++) {
								BVH_DEBUG_NEXT_STEP();
								kernel_assert(kernel_tex_fetch(__prim_type, prim_addr) == type);
								if(motion_triangle_intersect(kg,
								                             isect,
								                             P,
								                             dir,
								                             ray->time,
								                             visibility,
								                             object,
								                             prim_addr))
								{
									/* shadow ray early termination */
#  if defined(__KERNEL_SSE2__)
									if(visibility == PATH_RAY_SHADOW_OPAQUE)
										return true;
									tsplat = ssef(0.0f, 0.0f, -isect->t, -isect->t);
#    if BVH_FEATURE(BVH_HAIR)
									tfar = ssef(isect->t);
#    endif
#  else
									if(visibility == PATH_RAY_SHADOW_OPAQUE)
										return true;
#  endif
								}
							}
							break;
						}
#endif  /* BVH_FEATURE(BVH_MOTION) */
#if BVH_FEATURE(BVH_HAIR)
						case PRIMITIVE_CURVE:
						case PRIMITIVE_MOTION_CURVE: {
							for(; prim_addr < prim_addr2; prim_addr++) {
								BVH_DEBUG_NEXT_STEP();
								kernel_assert(kernel_tex_fetch(__prim_type, prim_addr) == type);
								bool hit;
								if(kernel_data.curve.curveflags & CURVE_KN_INTERPOLATE) {
									hit = bvh_cardinal_curve_intersect(kg,
									                                   isect,
									                                   P,
									                                   dir,
									                                   visibility,
									                                   object,
									                                   prim_addr,
									                                   ray->time,
									                                   type,
									                                   lcg_state,
									                                   difl,
									                                   extmax);
								}
								else {
									hit = bvh_curve_intersect(kg,
									                          isect,
									                          P,
									                          dir,
									                          visibility,
									                          object,
									                          prim_addr,
									                          ray->time,
									                          type,
									                          lcg_state,
									                          difl,
									                          extmax);
								}
								if(hit) {
									/* shadow ray early termination */
#  if defined(__KERNEL_SSE2__)
									if(visibility == PATH_RAY_SHADOW_OPAQUE)
										return true;
									tsplat = ssef(0.0f, 0.0f, -isect->t, -isect->t);
#    if BVH_FEATURE(BVH_HAIR)
									tfar = ssef(isect->t);
#    endif
#  else
									if(visibility == PATH_RAY_SHADOW_OPAQUE)
										return true;
#  endif
								}
							}
							break;
						}
#endif  /* BVH_FEATURE(BVH_HAIR) */
					}
				}
#if BVH_FEATURE(BVH_INSTANCING)
				else {
					/* instance push */
					object = kernel_tex_fetch(__prim_object, -prim_addr-1);

#  if BVH_FEATURE(BVH_MOTION)
					bvh_instance_motion_push(kg, object, ray, &P, &dir, &idir, &isect->t, &ob_itfm);
#  else
					bvh_instance_push(kg, object, ray, &P, &dir, &idir, &isect->t);
#  endif
					triangle_intersect_precalc(dir, &isect_precalc);

#  if defined(__KERNEL_SSE2__)
					Psplat[0] = ssef(P.x);
					Psplat[1] = ssef(P.y);
					Psplat[2] = ssef(P.z);

					tsplat = ssef(0.0f, 0.0f, -isect->t, -isect->t);
#    if BVH_FEATURE(BVH_HAIR)
					tfar = ssef(isect->t);
#    endif

					gen_idirsplat_swap(pn, shuf_identity, shuf_swap, idir, idirsplat, shufflexyz);
#  endif

					++stack_ptr;
					kernel_assert(stack_ptr < BVH_STACK_SIZE);
					traversal_stack[stack_ptr] = ENTRYPOINT_SENTINEL;

					node_addr = kernel_tex_fetch(__object_node, object);

					BVH_DEBUG_NEXT_INSTANCE();
				}
			}
#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 BVH_FEATURE(BVH_MOTION)
			bvh_instance_motion_pop(kg, object, ray, &P, &dir, &idir, &isect->t, &ob_itfm);
#  else
			bvh_instance_pop(kg, object, ray, &P, &dir, &idir, &isect->t);
#  endif
			triangle_intersect_precalc(dir, &isect_precalc);

#  if defined(__KERNEL_SSE2__)
			Psplat[0] = ssef(P.x);
			Psplat[1] = ssef(P.y);
			Psplat[2] = ssef(P.z);

			tsplat = ssef(0.0f, 0.0f, -isect->t, -isect->t);
#    if BVH_FEATURE(BVH_HAIR)
			tfar = ssef(isect->t);
#    endif

			gen_idirsplat_swap(pn, shuf_identity, shuf_swap, idir, idirsplat, shufflexyz);
#  endif

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

	return (isect->prim != PRIM_NONE);
}

ccl_device_inline bool BVH_FUNCTION_NAME(KernelGlobals *kg,
                                         const Ray *ray,
                                         Intersection *isect,
                                         const uint visibility
#if BVH_FEATURE(BVH_HAIR_MINIMUM_WIDTH)
                                         , uint *lcg_state,
                                         float difl,
                                         float extmax
#endif
                                         )
{
#ifdef __QBVH__
	if(kernel_data.bvh.use_qbvh) {
		return BVH_FUNCTION_FULL_NAME(QBVH)(kg,
		                                    ray,
		                                    isect,
		                                    visibility
#if BVH_FEATURE(BVH_HAIR_MINIMUM_WIDTH)
		                                    , lcg_state,
		                                    difl,
		                                    extmax
#endif
		                                    );
	}
	else
#endif
	{
		kernel_assert(kernel_data.bvh.use_qbvh == false);
		return BVH_FUNCTION_FULL_NAME(BVH)(kg,
		                                   ray,
		                                   isect,
		                                   visibility
#if BVH_FEATURE(BVH_HAIR_MINIMUM_WIDTH)
		                                   , lcg_state,
		                                   difl,
		                                   extmax
#endif
		                                   );
	}
}

#undef BVH_FUNCTION_NAME
#undef BVH_FUNCTION_FEATURES
#undef NODE_INTERSECT
#undef NODE_INTERSECT_ROBUST
