bvh_traversal.h

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/*
 * 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.
 */
 
#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_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();
 
  /* 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);
 
        {
          traverse_mask = NODE_INTERSECT(kg,
                                         P,
#if BVH_FEATURE(BVH_HAIR)
                                         dir,
#endif
                                         idir,
                                         isect->t,
                                         node_addr,
                                         visibility,
                                         dist);
        }
 
        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 (prim_addr >= 0) {
          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 (visibility & PATH_RAY_SHADOW_OPAQUE)
                    return true;
                }
              }
              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 (visibility & PATH_RAY_SHADOW_OPAQUE)
                    return true;
                }
              }
              break;
            }
#endif /* BVH_FEATURE(BVH_MOTION) */
#if BVH_FEATURE(BVH_HAIR)
            case PRIMITIVE_CURVE_THICK:
            case PRIMITIVE_MOTION_CURVE_THICK:
            case PRIMITIVE_CURVE_RIBBON:
            case PRIMITIVE_MOTION_CURVE_RIBBON: {
              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));
                const bool hit = curve_intersect(
                    kg, isect, P, dir, visibility, object, prim_addr, ray->time, curve_type);
                if (hit) {
                  /* shadow ray early termination */
                  if (visibility & PATH_RAY_SHADOW_OPAQUE)
                    return true;
                }
              }
              break;
            }
#endif /* BVH_FEATURE(BVH_HAIR) */
          }
        }
        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
 
          ++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();
        }
      }
    } while (node_addr != ENTRYPOINT_SENTINEL);
 
    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
 
      object = OBJECT_NONE;
      node_addr = traversal_stack[stack_ptr];
      --stack_ptr;
    }
  } 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)
{
  return BVH_FUNCTION_FULL_NAME(BVH)(kg, ray, isect, visibility);
}
 
#undef BVH_FUNCTION_NAME
#undef BVH_FUNCTION_FEATURES
#undef NODE_INTERSECT