Function GetSlopePixelZOnEdge

src/landscape.cpp:358–377

* Determine the Z height of the corners of a specific tile edge * * @note If a tile has a non-continuous halftile foundation, a corner can have different heights wrt. its edges. * * @pre z1 and z2 must be initialized (typ. with TileZ). The corner heights just get added. * * @param tileh The slope of the tile. * @param edge The edge of interest. * @param z1 Gets incremented by the height of

 * @param z2 Gets incremented by the height of the second corner of the edge. (far corner wrt. the camera)
 */
void GetSlopePixelZOnEdge(Slope tileh, DiagDirection edge, int &z1, int &z2)
{
	static const Slope corners[4][4] = {
		/*    corner     |          steep slope
		 *  z1      z2   |       z1             z2        */
		{SLOPE_E, SLOPE_N, SLOPE_STEEP_E, SLOPE_STEEP_N}, // DIAGDIR_NE, z1 = E, z2 = N
		{SLOPE_S, SLOPE_E, SLOPE_STEEP_S, SLOPE_STEEP_E}, // DIAGDIR_SE, z1 = S, z2 = E
		{SLOPE_S, SLOPE_W, SLOPE_STEEP_S, SLOPE_STEEP_W}, // DIAGDIR_SW, z1 = S, z2 = W
		{SLOPE_W, SLOPE_N, SLOPE_STEEP_W, SLOPE_STEEP_N}, // DIAGDIR_NW, z1 = W, z2 = N
	};

	int halftile_test = (IsHalftileSlope(tileh) ? SlopeWithOneCornerRaised(GetHalftileSlopeCorner(tileh)) : 0);
	if (halftile_test == corners[edge][0]) z2 += TILE_HEIGHT; // The slope is non-continuous in z2. z2 is on the upper side.
	if (halftile_test == corners[edge][1]) z1 += TILE_HEIGHT; // The slope is non-continuous in z1. z1 is on the upper side.

	if ((tileh & corners[edge][0]) != 0) z1 += TILE_HEIGHT; // z1 is raised
	if ((tileh & corners[edge][1]) != 0) z2 += TILE_HEIGHT; // z2 is raised
	if (RemoveHalftileSlope(tileh) == corners[edge][2]) z1 += TILE_HEIGHT; // z1 is highest corner of a steep slope
	if (RemoveHalftileSlope(tileh) == corners[edge][3]) z2 += TILE_HEIGHT; // z2 is highest corner of a steep slope
}

/**
 * Get slope of a tile on top of a (possible) foundation