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 /**
  16  * Return the slope of a given tile
  17  * @param tile Tile to compute slope of
  18  * @param h    If not \c NULL, pointer to storage of z height
  19  * @return Slope of the tile, except for the HALFTILE part
  20  */
  21 Slope GetTileSlope(TileIndex tile, int *h)
  22 {
  23         assert(tile < MapSize());
  24
  25         uint x = TileX(tile);
  26         uint y = TileY(tile);
  27
  28         if (x == MapMaxX() || y == MapMaxY() ||
  29                         ((x == 0 || y == 0) && _settings_game.construction.freeform_edges)) {
  30                 if (h != NULL) *h = TileHeight(tile);
  31                 return SLOPE_FLAT;
  32         }
  33
  34         int a = TileHeight(tile); // Height of the N corner
  35         int min = a; // Minimal height of all corners examined so far
  36         int b = TileHeight(tile + TileDiffXY(1, 0)); // Height of the W corner
  37         if (min > b) min = b;
  38         int c = TileHeight(tile + TileDiffXY(0, 1)); // Height of the E corner
  39         if (min > c) min = c;
  40         int d = TileHeight(tile + TileDiffXY(1, 1)); // Height of the S corner
  41         if (min > d) min = d;
  42
  43         /* Due to the fact that tiles must connect with each other without leaving gaps, the
  44          * biggest difference in height between any corner and 'min' is between 0, 1, or 2.
  45          *
  46          * Also, there is at most 1 corner with height difference of 2.
  47          */
  48
  49         uint r = SLOPE_FLAT; // Computed slope of the tile
  50
  51         /* For each corner if not equal to minimum height:
  52          *  - set the SLOPE_STEEP flag if the difference is 2
  53          *  - add the corresponding SLOPE_X constant to the computed slope
  54          */
  55         if ((a -= min) != 0) r += (--a << 4) + SLOPE_N;
  56         if ((c -= min) != 0) r += (--c << 4) + SLOPE_E;
  57         if ((d -= min) != 0) r += (--d << 4) + SLOPE_S;
  58         if ((b -= min) != 0) r += (--b << 4) + SLOPE_W;
  59
  60         if (h != NULL) *h = min;
  61
  62         return (Slope)r;
  63 }
  64
  65 /**
  66  * Get bottom height of the tile
  67  * @param tile Tile to compute height of
  68  * @return Minimum height of the tile
  69  */
  70 int GetTileZ(TileIndex tile)
  71 {
  72         if (TileX(tile) == MapMaxX() || TileY(tile) == MapMaxY()) return 0;
  73
  74         int h = TileHeight(tile); // N corner
  75         h = min(h, TileHeight(tile + TileDiffXY(1, 0))); // W corner
  76         h = min(h, TileHeight(tile + TileDiffXY(0, 1))); // E corner
  77         h = min(h, TileHeight(tile + TileDiffXY(1, 1))); // S corner
  78
  79         return h;
  80 }
  81
  82 /**
  83  * Get top height of the tile
  84  * @param t Tile to compute height of
  85  * @return Maximum height of the tile
  86  */
  87 int GetTileMaxZ(TileIndex t)
  88 {
  89         if (TileX(t) == MapMaxX() || TileY(t) == MapMaxY()) return 0;
  90
  91         int h = TileHeight(t); // N corner
  92         h = max<int>(h, TileHeight(t + TileDiffXY(1, 0))); // W corner
  93         h = max<int>(h, TileHeight(t + TileDiffXY(0, 1))); // E corner
  94         h = max<int>(h, TileHeight(t + TileDiffXY(1, 1))); // S corner
  95
  96         return h;
  97 }