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  * @param[out] h The lowest height of the four corners.
  22  * @return The slope.
  23  */
  24 static Slope GetTileSlopeGivenHeight(int hnorth, int hwest, int heast, int hsouth, int *h)
  25 {
  26         /* Due to the fact that tiles must connect with each other without leaving gaps, the
  27          * biggest difference in height between any corner and 'min' is between 0, 1, or 2.
  28          *
  29          * Also, there is at most 1 corner with height difference of 2.
  30          */
  31         int hminnw = std::min(hnorth, hwest);
  32         int hmines = std::min(heast, hsouth);
  33         int hmin = std::min(hminnw, hmines);
  34
  35         if (h != nullptr) *h = hmin;
  36
  37         int hmaxnw = std::max(hnorth, hwest);
  38         int hmaxes = std::max(heast, hsouth);
  39         int hmax = std::max(hmaxnw, hmaxes);
  40
  41         Slope r = SLOPE_FLAT;
  42
  43         if (hnorth != hmin) r |= SLOPE_N;
  44         if (hwest  != hmin) r |= SLOPE_W;
  45         if (heast  != hmin) r |= SLOPE_E;
  46         if (hsouth != hmin) r |= SLOPE_S;
  47
  48         if (hmax - hmin == 2) r |= SLOPE_STEEP;
  49
  50         return r;
  51 }
  52
  53 /**
  54  * Return the slope of a given tile inside the map.
  55  * @param tile Tile to compute slope of
  56  * @param h    If not \c nullptr, pointer to storage of z height
  57  * @return Slope of the tile, except for the HALFTILE part
  58  */
  59 Slope GetTileSlope(TileIndex tile, int *h)
  60 {
  61         uint x1 = TileX(tile);
  62         uint y1 = TileY(tile);
  63         uint x2 = std::min(x1 + 1, MapMaxX());
  64         uint y2 = std::min(y1 + 1, MapMaxY());
  65
  66         int hnorth = TileHeight(tile);           // Height of the North corner.
  67         int hwest  = TileHeight(TileXY(x2, y1)); // Height of the West corner.
  68         int heast  = TileHeight(TileXY(x1, y2)); // Height of the East corner.
  69         int hsouth = TileHeight(TileXY(x2, y2)); // Height of the South corner.
  70
  71         return GetTileSlopeGivenHeight(hnorth, hwest, heast, hsouth, h);
  72 }
  73
  74 /**
  75  * Return the slope of a given tile, also for tiles outside the map (virtual "black" tiles).
  76  *
  77  * @param x X coordinate of the tile to compute slope of, may be outside the map.
  78  * @param y Y coordinate of the tile to compute slope of, may be outside the map.
  79  * @param h If not \c nullptr, pointer to storage of z height.
  80  * @return Slope of the tile, except for the HALFTILE part.
  81  */
  82 Slope GetTilePixelSlopeOutsideMap(int x, int y, int *h)
  83 {
  84         int hnorth = TileHeightOutsideMap(x,     y);     // N corner.
  85         int hwest  = TileHeightOutsideMap(x + 1, y);     // W corner.
  86         int heast  = TileHeightOutsideMap(x,     y + 1); // E corner.
  87         int hsouth = TileHeightOutsideMap(x + 1, y + 1); // S corner.
  88
  89         Slope s = GetTileSlopeGivenHeight(hnorth, hwest, heast, hsouth, h);
  90         if (h != nullptr) *h *= TILE_HEIGHT;
  91         return s;
  92 }
  93
  94 /**
  95  * Check if a given tile is flat
  96  * @param tile Tile to check
  97  * @param h If not \c nullptr, pointer to storage of z height (only if tile is flat)
  98  * @return Whether the tile is flat
  99  */
 100 bool IsTileFlat(TileIndex tile, int *h)
 101 {
 102         uint x1 = TileX(tile);
 103         uint y1 = TileY(tile);
 104         uint x2 = std::min(x1 + 1, MapMaxX());
 105         uint y2 = std::min(y1 + 1, MapMaxY());
 106
 107         uint z = TileHeight(tile);
 108         if (TileHeight(TileXY(x2, y1)) != z) return false;
 109         if (TileHeight(TileXY(x1, y2)) != z) return false;
 110         if (TileHeight(TileXY(x2, y2)) != z) return false;
 111
 112         if (h != nullptr) *h = z;
 113         return true;
 114 }
 115
 116 /**
 117  * Get bottom height of the tile
 118  * @param tile Tile to compute height of
 119  * @return Minimum height of the tile
 120  */
 121 int GetTileZ(TileIndex tile)
 122 {
 123         uint x1 = TileX(tile);
 124         uint y1 = TileY(tile);
 125         uint x2 = std::min(x1 + 1, MapMaxX());
 126         uint y2 = std::min(y1 + 1, MapMaxY());
 127
 128         return std::min({
 129                 TileHeight(tile),           // N corner
 130                 TileHeight(TileXY(x2, y1)), // W corner
 131                 TileHeight(TileXY(x1, y2)), // E corner
 132                 TileHeight(TileXY(x2, y2)), // S corner
 133         });
 134 }
 135
 136 /**
 137  * Get top height of the tile inside the map.
 138  * @param t Tile to compute height of
 139  * @return Maximum height of the tile
 140  */
 141 int GetTileMaxZ(TileIndex t)
 142 {
 143         uint x1 = TileX(t);
 144         uint y1 = TileY(t);
 145         uint x2 = std::min(x1 + 1, MapMaxX());
 146         uint y2 = std::min(y1 + 1, MapMaxY());
 147
 148         return std::max({
 149                 TileHeight(t),              // N corner
 150                 TileHeight(TileXY(x2, y1)), // W corner
 151                 TileHeight(TileXY(x1, y2)), // E corner
 152                 TileHeight(TileXY(x2, y2)), // S corner
 153         });
 154 }