bvh_refit.h

// Copyright 2009-2021 Intel Corporation
// SPDX-License-Identifier: Apache-2.0

#pragma once

#include "../bvh/bvh.h"

namespace embree
{
  namespace isa
  {
    template<int N>
    class BVHNRefitter
    {
    public:

      /*! Type shortcuts */
      typedef BVHN<N> BVH;
      typedef typename BVH::AABBNode AABBNode;
      typedef typename BVH::NodeRef NodeRef;

      struct LeafBoundsInterface {
        virtual const BBox3fa leafBounds(NodeRef& ref) const = 0;
      };

    public:
    
      /*! Constructor. */
      BVHNRefitter (BVH* bvh, const LeafBoundsInterface& leafBounds);

      /*! refits the BVH */
      void refit();

    private:
      /* single-threaded subtree extraction based on BVH depth */
      void gather_subtree_refs(NodeRef& ref, 
                               size_t &subtrees,
                               const size_t depth = 0);

      /* single-threaded top-level refit */
      BBox3fa refit_toplevel(NodeRef& ref,
                             size_t &subtrees,
							 const BBox3fa *const subTreeBounds,
                             const size_t depth = 0);

      /* single-threaded subtree refit */
      BBox3fa recurse_bottom(NodeRef& ref);
      
    public:
      BVH* bvh;                              //!< BVH to refit
      const LeafBoundsInterface& leafBounds; //!< calculates bounds of leaves

      static const size_t MAX_SUB_TREE_EXTRACTION_DEPTH = (N==4) ? 4   : (N==8) ? 3    : 3;
      static const size_t MAX_NUM_SUB_TREES             = (N==4) ? 256 : (N==8) ? 512 : N*N*N; // N ^ MAX_SUB_TREE_EXTRACTION_DEPTH
      size_t numSubTrees;
      NodeRef subTrees[MAX_NUM_SUB_TREES];
    };

    template<int N, typename Mesh, typename Primitive>
    class BVHNRefitT : public Builder, public BVHNRefitter<N>::LeafBoundsInterface
    {
    public:
      
      /*! Type shortcuts */
      typedef BVHN<N> BVH;
      typedef typename BVH::AABBNode AABBNode;
      typedef typename BVH::NodeRef NodeRef;
      
    public:
      BVHNRefitT (BVH* bvh, Builder* builder, Mesh* mesh, size_t mode);

      virtual void build();
      
      virtual void clear();

      virtual const BBox3fa leafBounds (NodeRef& ref) const
      {
        size_t num; char* prim = ref.leaf(num);
        if (unlikely(ref == BVH::emptyNode)) return empty;

        BBox3fa bounds = empty;
        for (size_t i=0; i<num; i++)
            bounds.extend(((Primitive*)prim)[i].update(mesh));
        return bounds;
      }
      
    private:
      BVH* bvh;
      std::unique_ptr<Builder> builder;
      std::unique_ptr<BVHNRefitter<N>> refitter;
      Mesh* mesh;
      unsigned int topologyVersion;
    };
  }
}