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/* $Id$ */

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#include "stdafx.h"

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#include "tile.h"

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void SetMapExtraBits(TileIndex tile, byte bits)

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{

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	assert(tile < MapSize());

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	SB(_m[tile].extra, 0, 2, bits & 3);

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}

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uint GetMapExtraBits(TileIndex tile)

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{

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	assert(tile < MapSize());

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	return GB(_m[tile].extra, 0, 2);

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}

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/** Converts the heights of 4 corners into a tileh, and returns the minimum height of the tile

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  * @param n,w,e,s the four corners

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  * @param h uint pointer to write the height to

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  * @return the tileh

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*/

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uint GetTileh(uint n, uint w, uint e, uint s, uint *h)

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{

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	uint min = n;

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	uint r;

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	if (min >= w) min = w;

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	if (min >= e) min = e;

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	if (min >= s) min = s;

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	r = 0;

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	if ((n -= min) != 0) r += (--n << 4) + 8;

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	if ((e -= min) != 0) r += (--e << 4) + 4;

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	if ((s -= min) != 0) r += (--s << 4) + 2;

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	if ((w -= min) != 0) r += (--w << 4) + 1;

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	if (h != NULL) *h = min * 8;

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	return r;

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}

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uint GetTileSlope(TileIndex tile, uint *h)

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{

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	uint a;

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	uint b;

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	uint c;

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	uint d;

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	assert(tile < MapSize());

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	if (TileX(tile) == MapMaxX() || TileY(tile) == MapMaxY()) {

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		if (h != NULL) *h = 0;

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		return 0;

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	}

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	a = TileHeight(tile);

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	b = TileHeight(tile + TileDiffXY(1, 0));

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	c = TileHeight(tile + TileDiffXY(0, 1));

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	d = TileHeight(tile + TileDiffXY(1, 1));

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	return GetTileh(a, b, c, d, h);

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}

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uint GetTileZ(TileIndex tile)

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{

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	uint h;

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	GetTileSlope(tile, &h);

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	return h;

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}