src/tile_map.cpp

   1 /* $Id$ */
   2
   3 /*
   4  * This file is part of OpenTTD.
   5  * 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.
   6  * 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.
   7  * 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/>.
   8  */
   9
  10 /** @file tile_map.cpp Global tile accessors. */
  11
  12 #include "stdafx.h"
  13 #include "tile_map.h"
  14
  15 #include "safeguards.h"
  16
  17 /**
  18  * Get a tile's slope given the heigh of its four corners.
  19  * @param hnorth The height at the northern corner in the same unit as TileHeight.
  20  * @param hwest  The height at the western corner in the same unit as TileHeight.
  21  * @param heast  The height at the eastern corner in the same unit as TileHeight.
  22  * @param hsouth The height at the southern corner in the same unit as TileHeight.
  23  * @param[out] h The lowest height of the four corners.
  24  * @return The slope.
  25  */
  26 static Slope GetTileSlopeGivenHeight(int hnorth, int hwest, int heast, int hsouth, int *h)
  27 {
  28         /* Due to the fact that tiles must connect with each other without leaving gaps, the
  29          * biggest difference in height between any corner and 'min' is between 0, 1, or 2.
  30          *
  31          * Also, there is at most 1 corner with height difference of 2.
  32          */
  33         int hminnw = min(hnorth, hwest);
  34         int hmines = min(heast, hsouth);
  35         int hmin = min(hminnw, hmines);
  36
  37         if (h != nullptr) *h = hmin;
  38
  39         int hmaxnw = max(hnorth, hwest);
  40         int hmaxes = max(heast, hsouth);
  41         int hmax = max(hmaxnw, hmaxes);
  42
  43         Slope r = SLOPE_FLAT;
  44
  45         if (hnorth != hmin) r |= SLOPE_N;
  46         if (hwest  != hmin) r |= SLOPE_W;
  47         if (heast  != hmin) r |= SLOPE_E;
  48         if (hsouth != hmin) r |= SLOPE_S;
  49
  50         if (hmax - hmin == 2) r |= SLOPE_STEEP;
  51
  52         return r;
  53 }
  54
  55 /**
  56  * Return the slope of a given tile inside the map.
  57  * @param tile Tile to compute slope of
  58  * @param h    If not \c nullptr, pointer to storage of z height
  59  * @return Slope of the tile, except for the HALFTILE part
  60  */
  61 Slope GetTileSlope(TileIndex tile, int *h)
  62 {
  63         uint x1 = TileX(tile);
  64         uint y1 = TileY(tile);
  65         uint x2 = min(x1 + 1, MapMaxX());
  66         uint y2 = min(y1 + 1, MapMaxY());
  67
  68         int hnorth = TileHeight(tile);           // Height of the North corner.
  69         int hwest  = TileHeight(TileXY(x2, y1)); // Height of the West corner.
  70         int heast  = TileHeight(TileXY(x1, y2)); // Height of the East corner.
  71         int hsouth = TileHeight(TileXY(x2, y2)); // Height of the South corner.
  72
  73         return GetTileSlopeGivenHeight(hnorth, hwest, heast, hsouth, h);
  74 }
  75
  76 /**
  77  * Return the slope of a given tile, also for tiles outside the map (virtual "black" tiles).
  78  *
  79  * @param x X coordinate of the tile to compute slope of, may be ouside the map.
  80  * @param y Y coordinate of the tile to compute slope of, may be ouside the map.
  81  * @param h If not \c nullptr, pointer to storage of z height.
  82  * @return Slope of the tile, except for the HALFTILE part.
  83  */
  84 Slope GetTilePixelSlopeOutsideMap(int x, int y, int *h)
  85 {
  86         int hnorth = TileHeightOutsideMap(x,     y);     // N corner.
  87         int hwest  = TileHeightOutsideMap(x + 1, y);     // W corner.
  88         int heast  = TileHeightOutsideMap(x,     y + 1); // E corner.
  89         int hsouth = TileHeightOutsideMap(x + 1, y + 1); // S corner.
  90
  91         Slope s = GetTileSlopeGivenHeight(hnorth, hwest, heast, hsouth, h);
  92         if (h != nullptr) *h *= TILE_HEIGHT;
  93         return s;
  94 }
  95
  96 /**
  97  * Check if a given tile is flat
  98  * @param tile Tile to check
  99  * @param h If not \c nullptr, pointer to storage of z height (only if tile is flat)
 100  * @return Whether the tile is flat
 101  */
 102 bool IsTileFlat(TileIndex tile, int *h)
 103 {
 104         uint x1 = TileX(tile);
 105         uint y1 = TileY(tile);
 106         uint x2 = min(x1 + 1, MapMaxX());
 107         uint y2 = min(y1 + 1, MapMaxY());
 108
 109         uint z = TileHeight(tile);
 110         if (TileHeight(TileXY(x2, y1)) != z) return false;
 111         if (TileHeight(TileXY(x1, y2)) != z) return false;
 112         if (TileHeight(TileXY(x2, y2)) != z) return false;
 113
 114         if (h != nullptr) *h = z;
 115         return true;
 116 }
 117
 118 /**
 119  * Get bottom height of the tile
 120  * @param tile Tile to compute height of
 121  * @return Minimum height of the tile
 122  */
 123 int GetTileZ(TileIndex tile)
 124 {
 125         uint x1 = TileX(tile);
 126         uint y1 = TileY(tile);
 127         uint x2 = min(x1 + 1, MapMaxX());
 128         uint y2 = min(y1 + 1, MapMaxY());
 129
 130         int h =    TileHeight(tile);            // N corner
 131         h = min(h, TileHeight(TileXY(x2, y1))); // W corner
 132         h = min(h, TileHeight(TileXY(x1, y2))); // E corner
 133         h = min(h, TileHeight(TileXY(x2, y2))); // S corner
 134
 135         return h;
 136 }
 137
 138 /**
 139  * Get top height of the tile inside the map.
 140  * @param t Tile to compute height of
 141  * @return Maximum height of the tile
 142  */
 143 int GetTileMaxZ(TileIndex t)
 144 {
 145         uint x1 = TileX(t);
 146         uint y1 = TileY(t);
 147         uint x2 = min(x1 + 1, MapMaxX());
 148         uint y2 = min(y1 + 1, MapMaxY());
 149
 150         int h =         TileHeight(t);               // N corner
 151         h = max<int>(h, TileHeight(TileXY(x2, y1))); // W corner
 152         h = max<int>(h, TileHeight(TileXY(x1, y2))); // E corner
 153         h = max<int>(h, TileHeight(TileXY(x2, y2))); // S corner
 154
 155         return h;
 156 }