binning.h

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/* SPDX-FileCopyrightText: 2009-2011 Intel Corporation
 * SPDX-FileCopyrightText: 2012-2022 Blender Foundation
 *
 * SPDX-License-Identifier: Apache-2.0
 *
 * Adapted code from Intel Corporation. */
 
#pragma once
 
#include "bvh/params.h"
#include "bvh/unaligned.h"
 
#include "util/types.h"
 
CCL_NAMESPACE_BEGIN
 
class BVHBuild;
 
/* Single threaded object binner. Finds the split with the best SAH heuristic
 * by testing for each dimension multiple partitionings for regular spaced
 * partition locations. A partitioning for a partition location is computed,
 * by putting primitives whose centroid is on the left and right of the split
 * location to different sets. The SAH is evaluated by computing the number of
 * blocks occupied by the primitives in the partitions. */
 
class BVHObjectBinning : public BVHRange {
 public:
  __forceinline BVHObjectBinning() : leafSAH(FLT_MAX) {}
 
  BVHObjectBinning(const BVHRange &job,
                   BVHReference *prims,
                   const BVHUnaligned *unaligned_heuristic = nullptr,
                   const Transform *aligned_space = nullptr);
 
  void split(BVHReference *prims, BVHObjectBinning &left_o, BVHObjectBinning &right_o) const;
 
  __forceinline const BoundBox &unaligned_bounds()
  {
    return bounds_;
  }
 
  float splitSAH; /* SAH cost of the best split */
  float leafSAH;  /* SAH cost of creating a leaf */
 
 protected:
  int dim;         /* best split dimension */
  int pos;         /* best split position */
  size_t num_bins; /* actual number of bins to use */
  float3 scale;    /* scaling factor to compute bin */
 
  /* Effective bounds and centroid bounds. */
  BoundBox bounds_;
  BoundBox cent_bounds_;
 
  const BVHUnaligned *unaligned_heuristic_;
  const Transform *aligned_space_;
 
  enum { MAX_BINS = 32 };
  enum { LOG_BLOCK_SIZE = 2 };
 
  /* computes the bin numbers for each dimension for a box. */
  __forceinline int4 get_bin(const BoundBox &box) const
  {
    const int4 a = make_int4((box.center2() - cent_bounds_.min) * scale - make_float3(0.5f));
    const int4 mn = make_int4(0);
    const int4 mx = make_int4((int)num_bins - 1);
 
    return clamp(a, mn, mx);
  }
 
  /* computes the bin numbers for each dimension for a point. */
  __forceinline int4 get_bin(const float3 &c) const
  {
    return make_int4((c - cent_bounds_.min) * scale - make_float3(0.5f));
  }
 
  /* compute the number of blocks occupied for each dimension. */
  __forceinline float4 blocks(const int4 &a) const
  {
    return make_float4((a + make_int4((1 << LOG_BLOCK_SIZE) - 1)) >> LOG_BLOCK_SIZE);
  }
 
  /* compute the number of blocks occupied in one dimension. */
  __forceinline int blocks(const size_t a) const
  {
    return (int)((a + ((1LL << LOG_BLOCK_SIZE) - 1)) >> LOG_BLOCK_SIZE);
  }
 
  __forceinline BoundBox get_prim_bounds(const BVHReference &prim) const
  {
    if (aligned_space_ == nullptr) {
      return prim.bounds();
    }
    return unaligned_heuristic_->compute_aligned_prim_boundbox(prim, *aligned_space_);
  }
};
 
CCL_NAMESPACE_END