(svn r10686) -Fix [FS#1058]: determining whether there is a tunnel going under the lowered area is only needed in two directions instead of all four, so take the directions (one for each axis) to the nearest border (along the given axis). Furthermore GetTileZ did much more than absolutely necessary.

src/tile.cpp

@@ -23,11 +23,11 @@ Slope GetTileSlope(TileIndex tile, uint *h)
 
 	min = a = TileHeight(tile);
 	b = TileHeight(tile + TileDiffXY(1, 0));
-	if (min >= b) min = b;
+	if (min > b) min = b;
 	c = TileHeight(tile + TileDiffXY(0, 1));
-	if (min >= c) min = c;
+	if (min > c) min = c;
 	d = TileHeight(tile + TileDiffXY(1, 1));
-	if (min >= d) min = d;
+	if (min > d) min = d;
 
 	r = SLOPE_FLAT;
 	if ((a -= min) != 0) r += (--a << 4) + SLOPE_N;
@@ -42,24 +42,25 @@ Slope GetTileSlope(TileIndex tile, uint *h)
 
 uint GetTileZ(TileIndex tile)
 {
-	uint h;
-	GetTileSlope(tile, &h);
-	return h;
+	if (TileX(tile) == MapMaxX() || TileY(tile) == MapMaxY()) return 0;
+
+	uint h = TileHeight(tile);
+	h = min(h, TileHeight(tile + TileDiffXY(1, 0)));
+	h = min(h, TileHeight(tile + TileDiffXY(0, 1)));
+	h = min(h, TileHeight(tile + TileDiffXY(1, 1)));
+
+	return h * TILE_HEIGHT;
 }
 
 
 uint GetTileMaxZ(TileIndex t)
 {
-	uint max;
-	uint h;
-
-	h = TileHeight(t);
-	max = h;
-	h = TileHeight(t + TileDiffXY(1, 0));
-	if (h > max) max = h;
-	h = TileHeight(t + TileDiffXY(0, 1));
-	if (h > max) max = h;
-	h = TileHeight(t + TileDiffXY(1, 1));
-	if (h > max) max = h;
-	return max * 8;
+	if (TileX(tile) == MapMaxX() || TileY(tile) == MapMaxY()) return 0;
+
+	uint h = TileHeight(t);
+	h = max(h, TileHeight(t + TileDiffXY(1, 0)));
+	h = max(h, TileHeight(t + TileDiffXY(0, 1)));
+	h = max(h, TileHeight(t + TileDiffXY(1, 1)));
+
+	return h * TILE_HEIGHT;
 }

src/tunnel_map.cpp

@@ -64,8 +64,6 @@ bool IsTunnelInWayDir(TileIndex tile, uint z, DiagDirection dir)
 bool IsTunnelInWay(TileIndex tile, uint z)
 {
 	return
-		IsTunnelInWayDir(tile, z, DIAGDIR_NE) ||
-		IsTunnelInWayDir(tile, z, DIAGDIR_SE) ||
-		IsTunnelInWayDir(tile, z, DIAGDIR_SW) ||
-		IsTunnelInWayDir(tile, z, DIAGDIR_NW);
+		IsTunnelInWayDir(tile, z, (TileX(tile) > (MapMaxX() / 2)) ? DIAGDIR_NE : DIAGDIR_SW) ||
+		IsTunnelInWayDir(tile, z, (TileY(tile) > (MapMaxY() / 2)) ? DIAGDIR_NW : DIAGDIR_SE);
 }