tile_map.cpp

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00001 /* $Id: tile_map.cpp 17693 2009-10-04 17:16:41Z rubidium $ */
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 #include "core/math_func.hpp"
00015 
00021 Slope GetTileSlope(TileIndex tile, uint *h)
00022 {
00023   assert(tile < MapSize());
00024 
00025   if (TileX(tile) == MapMaxX() || TileY(tile) == MapMaxY() ||
00026       (_settings_game.construction.freeform_edges && (TileX(tile) == 0 || TileY(tile) == 0))) {
00027     if (h != NULL) *h = TileHeight(tile) * TILE_HEIGHT;
00028     return SLOPE_FLAT;
00029   }
00030 
00031   uint a = TileHeight(tile); // Height of the N corner
00032   uint min = a; // Minimal height of all corners examined so far
00033   uint b = TileHeight(tile + TileDiffXY(1, 0)); // Height of the W corner
00034   if (min > b) min = b;
00035   uint c = TileHeight(tile + TileDiffXY(0, 1)); // Height of the E corner
00036   if (min > c) min = c;
00037   uint d = TileHeight(tile + TileDiffXY(1, 1)); // Height of the S corner
00038   if (min > d) min = d;
00039 
00040   /* Due to the fact that tiles must connect with each other without leaving gaps, the
00041    * biggest difference in height between any corner and 'min' is between 0, 1, or 2.
00042    *
00043    * Also, there is at most 1 corner with height difference of 2.
00044    */
00045 
00046   uint r = SLOPE_FLAT; // Computed slope of the tile
00047 
00048   /* For each corner if not equal to minimum height:
00049    *  - set the SLOPE_STEEP flag if the difference is 2
00050    *  - add the corresponding SLOPE_X constant to the computed slope
00051    */
00052   if ((a -= min) != 0) r += (--a << 4) + SLOPE_N;
00053   if ((c -= min) != 0) r += (--c << 4) + SLOPE_E;
00054   if ((d -= min) != 0) r += (--d << 4) + SLOPE_S;
00055   if ((b -= min) != 0) r += (--b << 4) + SLOPE_W;
00056 
00057   if (h != NULL) *h = min * TILE_HEIGHT;
00058 
00059   return (Slope)r;
00060 }
00061 
00066 uint GetTileZ(TileIndex tile)
00067 {
00068   if (TileX(tile) == MapMaxX() || TileY(tile) == MapMaxY()) return 0;
00069 
00070   uint h = TileHeight(tile); // N corner
00071   h = min(h, TileHeight(tile + TileDiffXY(1, 0))); // W corner
00072   h = min(h, TileHeight(tile + TileDiffXY(0, 1))); // E corner
00073   h = min(h, TileHeight(tile + TileDiffXY(1, 1))); // S corner
00074 
00075   return h * TILE_HEIGHT;
00076 }
00077 
00082 uint GetTileMaxZ(TileIndex t)
00083 {
00084   if (TileX(t) == MapMaxX() || TileY(t) == MapMaxY()) return 0;
00085 
00086   uint h = TileHeight(t); // N corner
00087   h = max(h, TileHeight(t + TileDiffXY(1, 0))); // W corner
00088   h = max(h, TileHeight(t + TileDiffXY(0, 1))); // E corner
00089   h = max(h, TileHeight(t + TileDiffXY(1, 1))); // S corner
00090 
00091   return h * TILE_HEIGHT;
00092 }

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