blender/intern/cycles/kernel/bvh/bvh_traversal.h

/*
 * 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 "kernel/bvh/qbvh_traversal.h"
#endif
#ifdef __KERNEL_AVX2__
#  include "kernel/bvh/obvh_traversal.h"
#endif

#if BVH_FEATURE(BVH_HAIR)
#  define NODE_INTERSECT bvh_node_intersect
#else
#  define NODE_INTERSECT bvh_aligned_node_intersect
#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_MOTION: motion blur rendering
 */

ccl_device_noinline bool BVH_FUNCTION_FULL_NAME(BVH)(KernelGlobals *kg,
                                                     const Ray *ray,
                                                     Intersection *isect,
                                                     const uint visibility)
{
  /* 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

  /* 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__)
        {
          traverse_mask = NODE_INTERSECT(kg,
                                         P,
#  if BVH_FEATURE(BVH_HAIR)
                                         dir,
#  endif
                                         idir,
                                         isect->t,
                                         node_addr,
                                         visibility,
                                         dist);
        }
#else  // __KERNEL_SSE2__
        {
          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_NODE();
      }

      /* 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_INTERSECTION();
                kernel_assert(kernel_tex_fetch(__prim_type, prim_addr) == type);
                if (triangle_intersect(kg, isect, P, dir, 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_INTERSECTION();
                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_INTERSECTION();
                const uint curve_type = kernel_tex_fetch(__prim_type, prim_addr);
                kernel_assert((curve_type & PRIMITIVE_ALL) == (type & PRIMITIVE_ALL));
                bool hit;
                if (kernel_data.curve.curveflags & CURVE_KN_INTERPOLATE) {
                  hit = cardinal_curve_intersect(
                      kg, isect, P, dir, visibility, object, prim_addr, ray->time, curve_type);
                }
                else {
                  hit = curve_intersect(
                      kg, isect, P, dir, visibility, object, prim_addr, ray->time, curve_type);
                }
                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)
          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

#  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)
      isect->t = bvh_instance_motion_pop(kg, object, ray, &P, &dir, &idir, isect->t, &ob_itfm);
#  else
      isect->t = bvh_instance_pop(kg, object, ray, &P, &dir, &idir, isect->t);
#  endif

#  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)
{
  switch (kernel_data.bvh.bvh_layout) {
#ifdef __KERNEL_AVX2__
    case BVH_LAYOUT_BVH8:
      return BVH_FUNCTION_FULL_NAME(OBVH)(kg, ray, isect, visibility);
#endif
#ifdef __QBVH__
    case BVH_LAYOUT_BVH4:
      return BVH_FUNCTION_FULL_NAME(QBVH)(kg, ray, isect, visibility);
#endif /* __QBVH__ */
    case BVH_LAYOUT_BVH2:
      return BVH_FUNCTION_FULL_NAME(BVH)(kg, ray, isect, visibility);
  }
  kernel_assert(!"Should not happen");
  return false;
}

#undef BVH_FUNCTION_NAME
#undef BVH_FUNCTION_FEATURES
#undef NODE_INTERSECT