Method build_node

src/bvh/build.cpp:712–799

multithreaded binning builder */

/* multithreaded binning builder */
unique_ptr<BVHNode> BVHBuild::build_node(const BVHObjectBinning &range, const int level)
{
  const size_t size = range.size();
  const float leafSAH = params.sah_primitive_cost * range.leafSAH;
  const float splitSAH = params.sah_node_cost * range.bounds().half_area() +
                         params.sah_primitive_cost * range.splitSAH;

  /* Have at least one inner node on top level, for performance and correct
   * visibility tests, since object instances do not check visibility flag.
   */
  if (!(range.size() > 0 && params.top_level && level == 0)) {
    /* Make leaf node when threshold reached or SAH tells us. */
    if ((params.small_enough_for_leaf(size, level)) ||
        (range_within_max_leaf_size(range, references) && leafSAH < splitSAH))
    {
      return create_leaf_node(range, references);
    }
  }

  BVHObjectBinning unaligned_range;
  float unalignedSplitSAH = FLT_MAX;
  float unalignedLeafSAH = FLT_MAX;
  Transform aligned_space;
  bool do_unalinged_split = false;
  if (params.use_unaligned_nodes && splitSAH > params.unaligned_split_threshold * leafSAH) {
    aligned_space = unaligned_heuristic.compute_aligned_space(range, references.data());
    unaligned_range = BVHObjectBinning(
        range, references.data(), &unaligned_heuristic, &aligned_space);
    unalignedSplitSAH = params.sah_node_cost * unaligned_range.unaligned_bounds().half_area() +
                        params.sah_primitive_cost * unaligned_range.splitSAH;
    unalignedLeafSAH = params.sah_primitive_cost * unaligned_range.leafSAH;
    if (!(range.size() > 0 && params.top_level && level == 0)) {
      if (unalignedLeafSAH < unalignedSplitSAH && unalignedSplitSAH < splitSAH &&
          range_within_max_leaf_size(range, references))
      {
        return create_leaf_node(range, references);
      }
    }
    /* Check whether unaligned split is better than the regular one. */
    if (unalignedSplitSAH < splitSAH) {
      do_unalinged_split = true;
    }
  }

  /* Perform split. */
  BVHObjectBinning left;
  BVHObjectBinning right;
  if (do_unalinged_split) {
    unaligned_range.split(references.data(), left, right);
  }
  else {
    range.split(references.data(), left, right);
  }

  BoundBox bounds;
  if (do_unalinged_split) {
    bounds = unaligned_heuristic.compute_aligned_boundbox(range, references.data(), aligned_space);
  }