test2/source/blender/freestyle/intern/geometry/HashGrid.h

/* SPDX-FileCopyrightText: 2023 Blender Authors
 *
 * SPDX-License-Identifier: GPL-2.0-or-later */

#pragma once

/** \file
 * \ingroup freestyle
 * \brief Class to define a cell grid surrounding the bounding box of the scene
 */

#if 0
#  if defined(__GNUC__) && (__GNUC__ >= 3)
// hash_map is not part of the C++ standard anymore;
// hash_map.h has been kept though for backward compatibility
#    include <hash_map.h>
#  else
#    include <hash_map>
#  endif
#endif

#include <map>

#include "Grid.h"

namespace Freestyle {

/** Defines a hash table used for searching the Cells */
struct GridHasher {
#define _MUL 950706376UL
#define _MOD 2147483647UL
  inline size_t operator()(const Vec3u &p) const
  {
    size_t res = (ulong(p[0] * _MUL)) % _MOD;
    res = ((res + ulong(p[1]) * _MUL)) % _MOD;
    return ((res + ulong(p[2]) * _MUL)) % _MOD;
  }
#undef _MUL
#undef _MOD
};

/** Class to define a regular grid used for ray casting computations */
class HashGrid : public Grid {
 public:
  typedef map<Vec3u, Cell *> GridHashTable;

  HashGrid() : Grid() {}

  virtual ~HashGrid()
  {
    clear();
  }

  /** clears the grid
   *  Deletes all the cells, clears the hash-table, resets size, size of cell, number of cells.
   */
  virtual void clear();

  /** Sets the different parameters of the grid
   *    orig
   *      The grid origin
   *    size
   *      The grid's dimensions
   *    nb
   *      The number of cells of the grid
   */
  virtual void configure(const Vec3r &orig, const Vec3r &size, uint nb);

  /** returns the cell whose coordinates are passed as argument */
  virtual Cell *getCell(const Vec3u &p)
  {
    Cell *found_cell = nullptr;

    GridHashTable::const_iterator found = _cells.find(p);
    if (found != _cells.end()) {
      found_cell = (*found).second;
    }
    return found_cell;
  }

  /** Fills the case p with the cell iCell */
  virtual void fillCell(const Vec3u &p, Cell &cell)
  {
    _cells[p] = &cell;
  }

 protected:
  GridHashTable _cells;
};

} /* namespace Freestyle */