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/* $Id$ */
/*
* 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"
/**
* Returns the tile height for a coordinate outside map. Such a height is
* needed for painting the area outside map using completely black tiles.
* The idea is descending to heightlevel 0 as fast as possible.
* @param x The X-coordinate (same unit as TileX).
* @param y The Y-coordinate (same unit as TileY).
* @return The height in the same unit as TileHeight.
*/
uint TileHeightOutsideMap(int x, int y)
{
/* In all cases: Descend to heightlevel 0 as fast as possible.
* So: If we are at the 0-side of the map (x<0 or y<0), we must
* subtract the distance to coordinate 0 from the heightlevel at
* coordinate 0.
* In other words: Subtract e.g. -x. If we are at the MapMax
* side of the map, we also need to subtract the distance to
* the edge of map, e.g. MapMaxX - x.
*
* NOTE: Assuming constant heightlevel outside map would be
* simpler here. However, then we run into painting problems,
* since whenever a heightlevel change at the map border occurs,
* we would need to repaint anything outside map.
* In contrast, by doing it this way, we can localize this change,
* which means we may assume constant heightlevel for all tiles
* at more than <heightlevel at map border> distance from the
* map border.
*/
if (x < 0) {
if (y < 0) {
return max((int)TileHeight(TileXY(0, 0)) - (-x) - (-y), 0);
} else if (y < (int)MapMaxY()) {
return max((int)TileHeight(TileXY(0, y)) - (-x), 0);
} else {
return max((int)TileHeight(TileXY(0, (int)MapMaxY())) - (-x) - (y - (int)MapMaxY()), 0);
}
} else if (x < (int)MapMaxX()) {
if (y < 0) {
return max((int)TileHeight(TileXY(x, 0)) - (-y), 0);
} else if (y < (int)MapMaxY()) {
return TileHeight(TileXY(x, y));
} else {
return max((int)TileHeight(TileXY(x, (int)MapMaxY())) - (y - (int)MapMaxY()), 0);
}
} else {
if (y < 0) {
return max((int)TileHeight(TileXY((int)MapMaxX(), 0)) - (x - (int)MapMaxX()) - (-y), 0);
} else if (y < (int)MapMaxY()) {
return max((int)TileHeight(TileXY((int)MapMaxX(), y)) - (x - (int)MapMaxX()), 0);
} else {
return max((int)TileHeight(TileXY((int)MapMaxX(), (int)MapMaxY())) - (x - (int)MapMaxX()) - (y - (int)MapMaxY()), 0);
}
}
}
/**
* 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 != NULL) *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 NULL, pointer to storage of z height
* @return Slope of the tile, except for the HALFTILE part
*/
Slope GetTileSlope(TileIndex tile, int *h)
{
assert(tile < MapSize());
uint x = TileX(tile);
uint y = TileY(tile);
if (x == MapMaxX() || y == MapMaxY()) {
if (h != NULL) *h = TileHeight(tile);
return SLOPE_FLAT;
}
int hnorth = TileHeight(tile); // Height of the North corner.
int hwest = TileHeight(tile + TileDiffXY(1, 0)); // Height of the West corner.
int heast = TileHeight(tile + TileDiffXY(0, 1)); // Height of the East corner.
int hsouth = TileHeight(tile + TileDiffXY(1, 1)); // Height of the South corner.
return GetTileSlopeGivenHeight(hnorth, hwest, heast, hsouth, h);
}
/**
* Return the slope of a given tile outside the map.
*
* @param x X-coordinate of the tile outside to compute height of.
* @param y Y-coordinate of the tile outside to compute height of.
* @param h If not \c NULL, pointer to storage of z height.
* @return Slope of the tile outside map, 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 != NULL) *h *= TILE_HEIGHT;
return s;
}
/**
* Check if a given tile is flat
* @param tile Tile to check
* @param h If not \c NULL, pointer to storage of z height (only if tile is flat)
* @return Whether the tile is flat
*/
bool IsTileFlat(TileIndex tile, int *h)
{
assert(tile < MapSize());
if (!IsInnerTile(tile)) {
if (h != NULL) *h = TileHeight(tile);
return true;
}
uint z = TileHeight(tile);
if (TileHeight(tile + TileDiffXY(1, 0)) != z) return false;
if (TileHeight(tile + TileDiffXY(0, 1)) != z) return false;
if (TileHeight(tile + TileDiffXY(1, 1)) != z) return false;
if (h != NULL) *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)
{
if (TileX(tile) == MapMaxX() || TileY(tile) == MapMaxY()) return 0;
int 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;
}
/**
* 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)
{
if (TileX(t) == MapMaxX() || TileY(t) == MapMaxY()) return TileHeightOutsideMap(TileX(t), TileY(t));
int h = TileHeight(t); // N corner
h = max<int>(h, TileHeight(t + TileDiffXY(1, 0))); // W corner
h = max<int>(h, TileHeight(t + TileDiffXY(0, 1))); // E corner
h = max<int>(h, TileHeight(t + TileDiffXY(1, 1))); // S corner
return h;
}
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