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/*
* This file is part of OpenTTD.
* 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.
* 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.
* 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/>.
*/
/** @file tile_map.cpp Global tile accessors. */
#include "stdafx.h"
#include "tile_map.h"
#include "safeguards.h"
/**
* Get a tile's slope given the heigh of its four corners.
* @param hnorth The height at the northern corner in the same unit as TileHeight.
* @param hwest The height at the western corner in the same unit as TileHeight.
* @param heast The height at the eastern corner in the same unit as TileHeight.
* @param hsouth The height at the southern corner in the same unit as TileHeight.
* @param[out] h The lowest height of the four corners.
* @return The slope.
*/
static Slope GetTileSlopeGivenHeight(int hnorth, int hwest, int heast, int hsouth, int *h)
{
/* 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.
*/
int hminnw = min(hnorth, hwest);
int hmines = min(heast, hsouth);
int hmin = min(hminnw, hmines);
if (h != nullptr) *h = hmin;
int hmaxnw = max(hnorth, hwest);
int hmaxes = max(heast, hsouth);
int hmax = max(hmaxnw, hmaxes);
Slope r = SLOPE_FLAT;
if (hnorth != hmin) r |= SLOPE_N;
if (hwest != hmin) r |= SLOPE_W;
if (heast != hmin) r |= SLOPE_E;
if (hsouth != hmin) r |= SLOPE_S;
if (hmax - hmin == 2) r |= SLOPE_STEEP;
return r;
}
/**
* Return the slope of a given tile inside the map.
* @param tile Tile to compute slope of
* @param h If not \c nullptr, pointer to storage of z height
* @return Slope of the tile, except for the HALFTILE part
*/
Slope GetTileSlope(TileIndex tile, int *h)
{
uint x1 = TileX(tile);
uint y1 = TileY(tile);
uint x2 = min(x1 + 1, MapMaxX());
uint y2 = min(y1 + 1, MapMaxY());
int hnorth = TileHeight(tile); // Height of the North corner.
int hwest = TileHeight(TileXY(x2, y1)); // Height of the West corner.
int heast = TileHeight(TileXY(x1, y2)); // Height of the East corner.
int hsouth = TileHeight(TileXY(x2, y2)); // Height of the South corner.
return GetTileSlopeGivenHeight(hnorth, hwest, heast, hsouth, h);
}
/**
* Return the slope of a given tile, also for tiles outside the map (virtual "black" tiles).
*
* @param x X coordinate of the tile to compute slope of, may be outside the map.
* @param y Y coordinate of the tile to compute slope of, may be outside the map.
* @param h If not \c nullptr, pointer to storage of z height.
* @return Slope of the tile, except for the HALFTILE part.
*/
Slope GetTilePixelSlopeOutsideMap(int x, int y, int *h)
{
int hnorth = TileHeightOutsideMap(x, y); // N corner.
int hwest = TileHeightOutsideMap(x + 1, y); // W corner.
int heast = TileHeightOutsideMap(x, y + 1); // E corner.
int hsouth = TileHeightOutsideMap(x + 1, y + 1); // S corner.
Slope s = GetTileSlopeGivenHeight(hnorth, hwest, heast, hsouth, h);
if (h != nullptr) *h *= TILE_HEIGHT;
return s;
}
/**
* Check if a given tile is flat
* @param tile Tile to check
* @param h If not \c nullptr, pointer to storage of z height (only if tile is flat)
* @return Whether the tile is flat
*/
bool IsTileFlat(TileIndex tile, int *h)
{
uint x1 = TileX(tile);
uint y1 = TileY(tile);
uint x2 = min(x1 + 1, MapMaxX());
uint y2 = min(y1 + 1, MapMaxY());
uint z = TileHeight(tile);
if (TileHeight(TileXY(x2, y1)) != z) return false;
if (TileHeight(TileXY(x1, y2)) != z) return false;
if (TileHeight(TileXY(x2, y2)) != z) return false;
if (h != nullptr) *h = z;
return true;
}
/**
* Get bottom height of the tile
* @param tile Tile to compute height of
* @return Minimum height of the tile
*/
int GetTileZ(TileIndex tile)
{
uint x1 = TileX(tile);
uint y1 = TileY(tile);
uint x2 = min(x1 + 1, MapMaxX());
uint y2 = min(y1 + 1, MapMaxY());
int h = TileHeight(tile); // N corner
h = min(h, TileHeight(TileXY(x2, y1))); // W corner
h = min(h, TileHeight(TileXY(x1, y2))); // E corner
h = min(h, TileHeight(TileXY(x2, y2))); // S corner
return h;
}
/**
* Get top height of the tile inside the map.
* @param t Tile to compute height of
* @return Maximum height of the tile
*/
int GetTileMaxZ(TileIndex t)
{
uint x1 = TileX(t);
uint y1 = TileY(t);
uint x2 = min(x1 + 1, MapMaxX());
uint y2 = min(y1 + 1, MapMaxY());
int h = TileHeight(t); // N corner
h = max<int>(h, TileHeight(TileXY(x2, y1))); // W corner
h = max<int>(h, TileHeight(TileXY(x1, y2))); // E corner
h = max<int>(h, TileHeight(TileXY(x2, y2))); // S corner
return h;
}
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