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/* $Id$ */
/** @file tile_map.cpp Global tile accessors. */
#include "stdafx.h"
#include "openttd.h"
#include "tile_map.h"
#include "core/math_func.hpp"
/**
* Return the slope of a given tile
* @param tile Tile to compute slope of
* @param h If not \c NULL, pointer to storage of z height
* @return Slope of the tile, except for the HALFTILE part */
Slope GetTileSlope(TileIndex tile, uint *h)
{
assert(tile < MapSize());
if (TileX(tile) == MapMaxX() || TileY(tile) == MapMaxY()) {
if (h != NULL) *h = 0;
return SLOPE_FLAT;
}
uint a = TileHeight(tile); // Height of the N corner
uint min = a; // Minimal height of all corners examined so far
uint b = TileHeight(tile + TileDiffXY(1, 0)); // Height of the W corner
if (min > b) min = b;
uint c = TileHeight(tile + TileDiffXY(0, 1)); // Height of the E corner
if (min > c) min = c;
uint d = TileHeight(tile + TileDiffXY(1, 1)); // Height of the S corner
if (min > d) min = d;
/* Due to the fact that tiles must connect with each other without leaving gaps, the
* biggest difference in height between any corner and 'min' is between 0, 1, or 2.
*
* Also, there is at most 1 corner with height difference of 2.
*/
uint r = SLOPE_FLAT; // Computed slope of the tile
/* For each corner if not equal to minimum height:
* - set the SLOPE_STEEP flag if the difference is 2
* - add the corresponding SLOPE_X constant to the computed slope
*/
if ((a -= min) != 0) r += (--a << 4) + SLOPE_N;
if ((c -= min) != 0) r += (--c << 4) + SLOPE_E;
if ((d -= min) != 0) r += (--d << 4) + SLOPE_S;
if ((b -= min) != 0) r += (--b << 4) + SLOPE_W;
if (h != NULL) *h = min * TILE_HEIGHT;
return (Slope)r;
}
/**
* Get bottom height of the tile
* @param tile Tile to compute height of
* @return Minimum height of the tile */
uint GetTileZ(TileIndex tile)
{
if (TileX(tile) == MapMaxX() || TileY(tile) == MapMaxY()) return 0;
uint h = TileHeight(tile); // N corner
h = min(h, TileHeight(tile + TileDiffXY(1, 0))); // W corner
h = min(h, TileHeight(tile + TileDiffXY(0, 1))); // E corner
h = min(h, TileHeight(tile + TileDiffXY(1, 1))); // S corner
return h * TILE_HEIGHT;
}
/**
* Get top height of the tile
* @param tile Tile to compute height of
* @return Maximum height of the tile */
uint GetTileMaxZ(TileIndex t)
{
if (TileX(t) == MapMaxX() || TileY(t) == MapMaxY()) return 0;
uint h = TileHeight(t); // N corner
h = max(h, TileHeight(t + TileDiffXY(1, 0))); // W corner
h = max(h, TileHeight(t + TileDiffXY(0, 1))); // E corner
h = max(h, TileHeight(t + TileDiffXY(1, 1))); // S corner
return h * TILE_HEIGHT;
}
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