src/tile_map.cpp

   1 /*
   2  * This file is part of OpenTTD.
   3  * 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.
   4  * 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.
   5  * 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 <http://www.gnu.org/licenses/>.
   6  */
   7
   8 /** @file tile_map.cpp Global tile accessors. */
   9
  10 #include "stdafx.h"
  11 #include "tile_map.h"
  12
  13 #include "safeguards.h"
  14
  15 /**
  16  * Get a tile's slope given the heigh of its four corners.
  17  * @param hnorth The height at the northern corner in the same unit as TileHeight.
  18  * @param hwest  The height at the western corner in the same unit as TileHeight.
  19  * @param heast  The height at the eastern corner in the same unit as TileHeight.
  20  * @param hsouth The height at the southern corner in the same unit as TileHeight.
  21  * @return The slope and the lowest height of the four corners.
  22  */
  23 static std::tuple<Slope, int> GetTileSlopeGivenHeight(int hnorth, int hwest, int heast, int hsouth)
  24 {
  25         /* Due to the fact that tiles must connect with each other without leaving gaps, the
  26          * biggest difference in height between any corner and 'min' is between 0, 1, or 2.
  27          *
  28          * Also, there is at most 1 corner with height difference of 2.
  29          */
  30         int hminnw = std::min(hnorth, hwest);
  31         int hmines = std::min(heast, hsouth);
  32         int hmin = std::min(hminnw, hmines);
  33
  34         int hmaxnw = std::max(hnorth, hwest);
  35         int hmaxes = std::max(heast, hsouth);
  36         int hmax = std::max(hmaxnw, hmaxes);
  37
  38         Slope r = SLOPE_FLAT;
  39
  40         if (hnorth != hmin) r |= SLOPE_N;
  41         if (hwest  != hmin) r |= SLOPE_W;
  42         if (heast  != hmin) r |= SLOPE_E;
  43         if (hsouth != hmin) r |= SLOPE_S;
  44
  45         if (hmax - hmin == 2) r |= SLOPE_STEEP;
  46
  47         return {r, hmin};
  48 }
  49
  50 /**
  51  * Return the slope of a given tile inside the map.
  52  * @param tile Tile to compute slope of
  53  * @return Slope of the tile, except for the HALFTILE part, and the z height
  54  */
  55 std::tuple<Slope, int> GetTileSlopeZ(TileIndex tile)
  56 {
  57         uint x1 = TileX(tile);
  58         uint y1 = TileY(tile);
  59         uint x2 = std::min(x1 + 1, Map::MaxX());
  60         uint y2 = std::min(y1 + 1, Map::MaxY());
  61
  62         int hnorth = TileHeight(tile);           // Height of the North corner.
  63         int hwest  = TileHeight(TileXY(x2, y1)); // Height of the West corner.
  64         int heast  = TileHeight(TileXY(x1, y2)); // Height of the East corner.
  65         int hsouth = TileHeight(TileXY(x2, y2)); // Height of the South corner.
  66
  67         return GetTileSlopeGivenHeight(hnorth, hwest, heast, hsouth);
  68 }
  69
  70 /**
  71  * Return the slope of a given tile, also for tiles outside the map (virtual "black" tiles).
  72  *
  73  * @param x X coordinate of the tile to compute slope of, may be outside the map.
  74  * @param y Y coordinate of the tile to compute slope of, may be outside the map.
  75  * @param h If not \c nullptr, pointer to storage of z height.
  76  * @return Slope of the tile, except for the HALFTILE part, and the z height of the tile.
  77  */
  78 std::tuple<Slope, int> GetTilePixelSlopeOutsideMap(int x, int y)
  79 {
  80         int hnorth = TileHeightOutsideMap(x,     y);     // N corner.
  81         int hwest  = TileHeightOutsideMap(x + 1, y);     // W corner.
  82         int heast  = TileHeightOutsideMap(x,     y + 1); // E corner.
  83         int hsouth = TileHeightOutsideMap(x + 1, y + 1); // S corner.
  84
  85         auto [slope, h] = GetTileSlopeGivenHeight(hnorth, hwest, heast, hsouth);
  86         return {slope, h * TILE_HEIGHT};
  87 }
  88
  89 /**
  90  * Check if a given tile is flat
  91  * @param tile Tile to check
  92  * @param h If not \c nullptr, pointer to storage of z height (only if tile is flat)
  93  * @return Whether the tile is flat
  94  */
  95 bool IsTileFlat(TileIndex tile, int *h)
  96 {
  97         uint x1 = TileX(tile);
  98         uint y1 = TileY(tile);
  99         uint x2 = std::min(x1 + 1, Map::MaxX());
 100         uint y2 = std::min(y1 + 1, Map::MaxY());
 101
 102         uint z = TileHeight(tile);
 103         if (TileHeight(TileXY(x2, y1)) != z) return false;
 104         if (TileHeight(TileXY(x1, y2)) != z) return false;
 105         if (TileHeight(TileXY(x2, y2)) != z) return false;
 106
 107         if (h != nullptr) *h = z;
 108         return true;
 109 }
 110
 111 /**
 112  * Get bottom height of the tile
 113  * @param tile Tile to compute height of
 114  * @return Minimum height of the tile
 115  */
 116 int GetTileZ(TileIndex tile)
 117 {
 118         uint x1 = TileX(tile);
 119         uint y1 = TileY(tile);
 120         uint x2 = std::min(x1 + 1, Map::MaxX());
 121         uint y2 = std::min(y1 + 1, Map::MaxY());
 122
 123         return std::min({
 124                 TileHeight(tile),           // N corner
 125                 TileHeight(TileXY(x2, y1)), // W corner
 126                 TileHeight(TileXY(x1, y2)), // E corner
 127                 TileHeight(TileXY(x2, y2)), // S corner
 128         });
 129 }
 130
 131 /**
 132  * Get top height of the tile inside the map.
 133  * @param t Tile to compute height of
 134  * @return Maximum height of the tile
 135  */
 136 int GetTileMaxZ(TileIndex t)
 137 {
 138         uint x1 = TileX(t);
 139         uint y1 = TileY(t);
 140         uint x2 = std::min(x1 + 1, Map::MaxX());
 141         uint y2 = std::min(y1 + 1, Map::MaxY());
 142
 143         return std::max({
 144                 TileHeight(t),              // N corner
 145                 TileHeight(TileXY(x2, y1)), // W corner
 146                 TileHeight(TileXY(x1, y2)), // E corner
 147                 TileHeight(TileXY(x2, y2)), // S corner
 148         });
 149 }