tile_map.cpp

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00001 /* $Id: tile_map.cpp 25849 2013-10-12 22:07:58Z zuu $ */
00002 
00003 /*
00004  * This file is part of OpenTTD.
00005  * 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.
00006  * 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.
00007  * 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/>.
00008  */
00009 
00012 #include "stdafx.h"
00013 #include "tile_map.h"
00014 
00021 Slope GetTileSlope(TileIndex tile, int *h)
00022 {
00023   assert(tile < MapSize());
00024 
00025   if (!IsInnerTile(tile)) {
00026     if (h != NULL) *h = TileHeight(tile);
00027     return SLOPE_FLAT;
00028   }
00029 
00030   int a = TileHeight(tile); // Height of the N corner
00031   int min = a; // Minimal height of all corners examined so far
00032   int b = TileHeight(tile + TileDiffXY(1, 0)); // Height of the W corner
00033   if (min > b) min = b;
00034   int c = TileHeight(tile + TileDiffXY(0, 1)); // Height of the E corner
00035   if (min > c) min = c;
00036   int d = TileHeight(tile + TileDiffXY(1, 1)); // Height of the S corner
00037   if (min > d) min = d;
00038 
00039   /* Due to the fact that tiles must connect with each other without leaving gaps, the
00040    * biggest difference in height between any corner and 'min' is between 0, 1, or 2.
00041    *
00042    * Also, there is at most 1 corner with height difference of 2.
00043    */
00044 
00045   uint r = SLOPE_FLAT; // Computed slope of the tile
00046 
00047   /* For each corner if not equal to minimum height:
00048    *  - set the SLOPE_STEEP flag if the difference is 2
00049    *  - add the corresponding SLOPE_X constant to the computed slope
00050    */
00051   if ((a -= min) != 0) r += (--a << 4) + SLOPE_N;
00052   if ((c -= min) != 0) r += (--c << 4) + SLOPE_E;
00053   if ((d -= min) != 0) r += (--d << 4) + SLOPE_S;
00054   if ((b -= min) != 0) r += (--b << 4) + SLOPE_W;
00055 
00056   if (h != NULL) *h = min;
00057 
00058   return (Slope)r;
00059 }
00060 
00067 bool IsTileFlat(TileIndex tile, int *h)
00068 {
00069   assert(tile < MapSize());
00070 
00071   if (!IsInnerTile(tile)) {
00072     if (h != NULL) *h = TileHeight(tile);
00073     return true;
00074   }
00075 
00076   uint z = TileHeight(tile);
00077   if (TileHeight(tile + TileDiffXY(1, 0)) != z) return false;
00078   if (TileHeight(tile + TileDiffXY(0, 1)) != z) return false;
00079   if (TileHeight(tile + TileDiffXY(1, 1)) != z) return false;
00080 
00081   if (h != NULL) *h = z;
00082   return true;
00083 }
00084 
00090 int GetTileZ(TileIndex tile)
00091 {
00092   if (TileX(tile) == MapMaxX() || TileY(tile) == MapMaxY()) return 0;
00093 
00094   int h = TileHeight(tile); // N corner
00095   h = min(h, TileHeight(tile + TileDiffXY(1, 0))); // W corner
00096   h = min(h, TileHeight(tile + TileDiffXY(0, 1))); // E corner
00097   h = min(h, TileHeight(tile + TileDiffXY(1, 1))); // S corner
00098 
00099   return h;
00100 }
00101 
00107 int GetTileMaxZ(TileIndex t)
00108 {
00109   if (TileX(t) == MapMaxX() || TileY(t) == MapMaxY()) return 0;
00110 
00111   int h = TileHeight(t); // N corner
00112   h = max<int>(h, TileHeight(t + TileDiffXY(1, 0))); // W corner
00113   h = max<int>(h, TileHeight(t + TileDiffXY(0, 1))); // E corner
00114   h = max<int>(h, TileHeight(t + TileDiffXY(1, 1))); // S corner
00115 
00116   return h;
00117 }