tile_map.cpp

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/*
 * This file is part of OpenTTD.
 * OpenTTD is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, version 2.
 * OpenTTD is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
 * See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with OpenTTD. If not, see <https://www.gnu.org/licenses/old-licenses/gpl-2.0>.
 */

 
#include "stdafx.h"
#include "tile_map.h"
 
#include "safeguards.h"

static std::tuple<Slope, int> GetTileSlopeGivenHeight(int hnorth, int hwest, int heast, int hsouth)
{
  /* Due to the fact that tiles must connect with each other without leaving gaps, the
   * biggest difference in height between any corner and 'min' is between 0, 1, or 2.
   *
   * Also, there is at most 1 corner with height difference of 2.
   */
  int hminnw = std::min(hnorth, hwest);
  int hmines = std::min(heast, hsouth);
  int hmin = std::min(hminnw, hmines);
 
  int hmaxnw = std::max(hnorth, hwest);
  int hmaxes = std::max(heast, hsouth);
  int hmax = std::max(hmaxnw, hmaxes);
 
  Slope r = SLOPE_FLAT;
 
  if (hnorth != hmin) r |= SLOPE_N;
  if (hwest  != hmin) r |= SLOPE_W;
  if (heast  != hmin) r |= SLOPE_E;
  if (hsouth != hmin) r |= SLOPE_S;
 
  if (hmax - hmin == 2) r |= SLOPE_STEEP;
 
  return {r, hmin};
}

std::tuple<Slope, int> GetTileSlopeZ(TileIndex tile)
{
  uint x1 = TileX(tile);
  uint y1 = TileY(tile);
  uint x2 = std::min(x1 + 1, Map::MaxX());
  uint y2 = std::min(y1 + 1, Map::MaxY());
 
  int hnorth = TileHeight(tile);           // Height of the North corner.
  int hwest  = TileHeight(TileXY(x2, y1)); // Height of the West corner.
  int heast  = TileHeight(TileXY(x1, y2)); // Height of the East corner.
  int hsouth = TileHeight(TileXY(x2, y2)); // Height of the South corner.
 
  return GetTileSlopeGivenHeight(hnorth, hwest, heast, hsouth);
}

std::tuple<Slope, int> GetTilePixelSlopeOutsideMap(int x, int y)
{
  int hnorth = TileHeightOutsideMap(x,     y);     // N corner.
  int hwest  = TileHeightOutsideMap(x + 1, y);     // W corner.
  int heast  = TileHeightOutsideMap(x,     y + 1); // E corner.
  int hsouth = TileHeightOutsideMap(x + 1, y + 1); // S corner.
 
  auto [slope, h] = GetTileSlopeGivenHeight(hnorth, hwest, heast, hsouth);
  return {slope, h * TILE_HEIGHT};
}

bool IsTileFlat(TileIndex tile, int *h)
{
  uint x1 = TileX(tile);
  uint y1 = TileY(tile);
  uint x2 = std::min(x1 + 1, Map::MaxX());
  uint y2 = std::min(y1 + 1, Map::MaxY());
 
  uint z = TileHeight(tile);
  if (TileHeight(TileXY(x2, y1)) != z) return false;
  if (TileHeight(TileXY(x1, y2)) != z) return false;
  if (TileHeight(TileXY(x2, y2)) != z) return false;
 
  if (h != nullptr) *h = z;
  return true;
}

int GetTileZ(TileIndex tile)
{
  uint x1 = TileX(tile);
  uint y1 = TileY(tile);
  uint x2 = std::min(x1 + 1, Map::MaxX());
  uint y2 = std::min(y1 + 1, Map::MaxY());
 
  return std::min({
    TileHeight(tile),           // N corner
    TileHeight(TileXY(x2, y1)), // W corner
    TileHeight(TileXY(x1, y2)), // E corner
    TileHeight(TileXY(x2, y2)), // S corner
  });
}

int GetTileMaxZ(TileIndex t)
{
  uint x1 = TileX(t);
  uint y1 = TileY(t);
  uint x2 = std::min(x1 + 1, Map::MaxX());
  uint y2 = std::min(y1 + 1, Map::MaxY());
 
  return std::max({
    TileHeight(t),              // N corner
    TileHeight(TileXY(x2, y1)), // W corner
    TileHeight(TileXY(x1, y2)), // E corner
    TileHeight(TileXY(x2, y2)), // S corner
  });
}