src/tile_map.cpp

   1 /* $Id: tile_map.cpp 25849 2013-10-12 22:07:58Z zuu $ */
   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  * Returns the tile height for a coordinate outside map.  Such a height is
  19  * needed for painting the area outside map using completely black tiles.
  20  * The idea is descending to heightlevel 0 as fast as possible.
  21  * @param x The X-coordinate (same unit as TileX).
  22  * @param y The Y-coordinate (same unit as TileY).
  23  * @return The height in the same unit as TileHeight.
  24  */
  25 uint TileHeightOutsideMap(int x, int y)
  26 {
  27         /* In all cases: Descend to heightlevel 0 as fast as possible.
  28          * So: If we are at the 0-side of the map (x<0 or y<0), we must
  29          * subtract the distance to coordinate 0 from the heightlevel at
  30          * coordinate 0.
  31          * In other words: Subtract e.g. -x. If we are at the MapMax
  32          * side of the map, we also need to subtract the distance to
  33          * the edge of map, e.g. MapMaxX - x.
  34          *
  35          * NOTE: Assuming constant heightlevel outside map would be
  36          * simpler here. However, then we run into painting problems,
  37          * since whenever a heightlevel change at the map border occurs,
  38          * we would need to repaint anything outside map.
  39          * In contrast, by doing it this way, we can localize this change,
  40          * which means we may assume constant heightlevel for all tiles
  41          * at more than <heightlevel at map border> distance from the
  42          * map border.
  43          */
  44         if (x < 0) {
  45                 if (y < 0) {
  46                         return max((int)TileHeight(TileXY(0, 0)) - (-x) - (-y), 0);
  47                 } else if (y < (int)MapMaxY()) {
  48                         return max((int)TileHeight(TileXY(0, y)) - (-x), 0);
  49                 } else {
  50                         return max((int)TileHeight(TileXY(0, (int)MapMaxY())) - (-x) - (y - (int)MapMaxY()), 0);
  51                 }
  52         } else if (x < (int)MapMaxX()) {
  53                 if (y < 0) {
  54                         return max((int)TileHeight(TileXY(x, 0)) - (-y), 0);
  55                 } else if (y < (int)MapMaxY()) {
  56                         return TileHeight(TileXY(x, y));
  57                 } else {
  58                         return max((int)TileHeight(TileXY(x, (int)MapMaxY())) - (y - (int)MapMaxY()), 0);
  59                 }
  60         } else {
  61                 if (y < 0) {
  62                         return max((int)TileHeight(TileXY((int)MapMaxX(), 0)) - (x - (int)MapMaxX()) - (-y), 0);
  63                 } else if (y < (int)MapMaxY()) {
  64                         return max((int)TileHeight(TileXY((int)MapMaxX(), y)) - (x - (int)MapMaxX()), 0);
  65                 } else {
  66                         return max((int)TileHeight(TileXY((int)MapMaxX(), (int)MapMaxY())) - (x - (int)MapMaxX()) - (y - (int)MapMaxY()), 0);
  67                 }
  68         }
  69 }
  70
  71 /**
  72  * Get a tile's slope given the heigh of its four corners.
  73  * @param hnorth  The height at the northern corner in the same unit as TileHeight.
  74  * @param hwest   The height at the western corner in the same unit as TileHeight.
  75  * @param heast   The height at the eastern corner in the same unit as TileHeight.
  76  * @param hsouth  The height at the southern corner in the same unit as TileHeight.
  77  * @param [out] h The lowest height of the four corners.
  78  * @return The slope.
  79  */
  80 static Slope GetTileSlopeGivenHeight(int hnorth, int hwest, int heast, int hsouth, int *h)
  81 {
  82         /* Due to the fact that tiles must connect with each other without leaving gaps, the
  83          * biggest difference in height between any corner and 'min' is between 0, 1, or 2.
  84          *
  85          * Also, there is at most 1 corner with height difference of 2.
  86          */
  87         int hminnw = min(hnorth, hwest);
  88         int hmines = min(heast, hsouth);
  89         int hmin = min(hminnw, hmines);
  90
  91         if (h != NULL) *h = hmin;
  92
  93         int hmaxnw = max(hnorth, hwest);
  94         int hmaxes = max(heast, hsouth);
  95         int hmax = max(hmaxnw, hmaxes);
  96
  97         Slope r = SLOPE_FLAT;
  98
  99         if (hnorth != hmin) r |= SLOPE_N;
 100         if (hwest  != hmin) r |= SLOPE_W;
 101         if (heast  != hmin) r |= SLOPE_E;
 102         if (hsouth != hmin) r |= SLOPE_S;
 103
 104         if (hmax - hmin == 2) r |= SLOPE_STEEP;
 105
 106         return r;
 107 }
 108
 109 /**
 110  * Return the slope of a given tile inside the map.
 111  * @param tile Tile to compute slope of
 112  * @param h    If not \c NULL, pointer to storage of z height
 113  * @return Slope of the tile, except for the HALFTILE part
 114  */
 115 Slope GetTileSlope(TileIndex tile, int *h)
 116 {
 117         assert(tile < MapSize());
 118
 119         uint x = TileX(tile);
 120         uint y = TileY(tile);
 121         if (x == MapMaxX() || y == MapMaxY()) {
 122                 if (h != NULL) *h = TileHeight(tile);
 123                 return SLOPE_FLAT;
 124         }
 125
 126         int hnorth = TileHeight(tile);                    // Height of the North corner.
 127         int hwest  = TileHeight(tile + TileDiffXY(1, 0)); // Height of the West corner.
 128         int heast  = TileHeight(tile + TileDiffXY(0, 1)); // Height of the East corner.
 129         int hsouth = TileHeight(tile + TileDiffXY(1, 1)); // Height of the South corner.
 130
 131         return GetTileSlopeGivenHeight(hnorth, hwest, heast, hsouth, h);
 132 }
 133
 134 /**
 135  * Return the slope of a given tile outside the map.
 136  *
 137  * @param tile Tile outside the map to compute slope of.
 138  * @param h    If not \c NULL, pointer to storage of z height.
 139  * @return Slope of the tile outside map, except for the HALFTILE part.
 140  */
 141 Slope GetTilePixelSlopeOutsideMap(int x, int y, int *h)
 142 {
 143         int hnorth = TileHeightOutsideMap(x,     y);     // N corner.
 144         int hwest  = TileHeightOutsideMap(x + 1, y);     // W corner.
 145         int heast  = TileHeightOutsideMap(x,     y + 1); // E corner.
 146         int hsouth = TileHeightOutsideMap(x + 1, y + 1); // S corner.
 147
 148         Slope s = GetTileSlopeGivenHeight(hnorth, hwest, heast, hsouth, h);
 149         if (h != NULL) *h *= TILE_HEIGHT;
 150         return s;
 151 }
 152
 153 /**
 154  * Check if a given tile is flat
 155  * @param tile Tile to check
 156  * @param h If not \c NULL, pointer to storage of z height (only if tile is flat)
 157  * @return Whether the tile is flat
 158  */
 159 bool IsTileFlat(TileIndex tile, int *h)
 160 {
 161         assert(tile < MapSize());
 162
 163         if (!IsInnerTile(tile)) {
 164                 if (h != NULL) *h = TileHeight(tile);
 165                 return true;
 166         }
 167
 168         uint z = TileHeight(tile);
 169         if (TileHeight(tile + TileDiffXY(1, 0)) != z) return false;
 170         if (TileHeight(tile + TileDiffXY(0, 1)) != z) return false;
 171         if (TileHeight(tile + TileDiffXY(1, 1)) != z) return false;
 172
 173         if (h != NULL) *h = z;
 174         return true;
 175 }
 176
 177 /**
 178  * Get bottom height of the tile
 179  * @param tile Tile to compute height of
 180  * @return Minimum height of the tile
 181  */
 182 int GetTileZ(TileIndex tile)
 183 {
 184         if (TileX(tile) == MapMaxX() || TileY(tile) == MapMaxY()) return 0;
 185
 186         int h =    TileHeight(tile);                     // N corner
 187         h = min(h, TileHeight(tile + TileDiffXY(1, 0))); // W corner
 188         h = min(h, TileHeight(tile + TileDiffXY(0, 1))); // E corner
 189         h = min(h, TileHeight(tile + TileDiffXY(1, 1))); // S corner
 190
 191         return h;
 192 }
 193
 194 /**
 195  * Get bottom height of the tile outside map.
 196  *
 197  * @param tile Tile outside the map to compute height of.
 198  * @return Minimum height of the tile outside the map.
 199  */
 200 int GetTilePixelZOutsideMap(int x, int y)
 201 {
 202         uint h =   TileHeightOutsideMap(x,     y);      // N corner.
 203         h = min(h, TileHeightOutsideMap(x + 1, y));     // W corner.
 204         h = min(h, TileHeightOutsideMap(x,     y + 1)); // E corner.
 205         h = min(h, TileHeightOutsideMap(x + 1, y + 1)); // S corner
 206
 207         return h * TILE_HEIGHT;
 208 }
 209
 210 /**
 211  * Get top height of the tile inside the map.
 212  * @param t Tile to compute height of
 213  * @return Maximum height of the tile
 214  */
 215 int GetTileMaxZ(TileIndex t)
 216 {
 217         if (TileX(t) == MapMaxX() || TileY(t) == MapMaxY()) return TileHeightOutsideMap(TileX(t), TileY(t));
 218
 219         int h =         TileHeight(t);                     // N corner
 220         h = max<int>(h, TileHeight(t + TileDiffXY(1, 0))); // W corner
 221         h = max<int>(h, TileHeight(t + TileDiffXY(0, 1))); // E corner
 222         h = max<int>(h, TileHeight(t + TileDiffXY(1, 1))); // S corner
 223
 224         return h;
 225 }
 226
 227 /**
 228  * Get top height of the tile outside the map.
 229  *
 230  * @see Detailed description in header.
 231  *
 232  * @param tile Tile outside to compute height of.
 233  * @return Maximum height of the tile.
 234  */
 235 int GetTileMaxPixelZOutsideMap(int x, int y)
 236 {
 237         uint h =   TileHeightOutsideMap(x,     y);
 238         h = max(h, TileHeightOutsideMap(x + 1, y));
 239         h = max(h, TileHeightOutsideMap(x,     y + 1));
 240         h = max(h, TileHeightOutsideMap(x + 1, y + 1));
 241
 242         return h * TILE_HEIGHT;
 243 }