Precompute the neighbor offsets and distances

The distance of each brush point and the check for the center vertex
were recomputed for every vertex. Compute them once per paint() call
into typed arrays instead.

binaries/data/mods/public/maps/random/rmgen/painter/SmoothingPainter.js

@@ -26,6 +26,12 @@ SmoothingPainter.prototype.paint = function(area)
 	const brushPoints = getPointsInBoundingBox(getBoundingBox(
 		new Array(2).fill(0).map((zero, i) => new Vector2D(1, 1).mult(this.size).mult(i ? 1 : -1))));
 
+	// Offsets of the neighbors and their distances, excluding the center vertex.
+	const neighbors = brushPoints.filter(brushPoint => brushPoint.x || brushPoint.y);
+	const neighborX = Int32Array.from(neighbors, brushPoint => brushPoint.x);
+	const neighborY = Int32Array.from(neighbors, brushPoint => brushPoint.y);
+	const neighborDistance = Float64Array.from(neighbors, brushPoint => Math.abs(brushPoint.x) + Math.abs(brushPoint.y));
+
 	const vertexSize = g_Map.height.length;
 
 	// Additional complexity to process all 4 vertices of each tile, i.e the last row too
@@ -47,15 +53,14 @@ SmoothingPainter.prototype.paint = function(area)
 				let sumWeightedHeights = 0;
 				let sumWeights = 0;
 
-				for (const brushPoint of brushPoints)
+				for (let k = 0; k < neighborDistance.length; ++k)
 				{
-					const position = Vector2D.add(vertex, brushPoint);
-					const distance = Math.abs(brushPoint.x) + Math.abs(brushPoint.y);
-					if (!distance || !g_Map.validHeight(position))
+					const position = new Vector2D(vertex.x + neighborX[k], vertex.y + neighborY[k]);
+					if (!g_Map.validHeight(position))
 						continue;
 
-					sumWeightedHeights += g_Map.getHeight(position) / distance;
-					sumWeights += 1 / distance;
+					sumWeightedHeights += g_Map.getHeight(position) / neighborDistance[k];
+					sumWeights += 1 / neighborDistance[k];
 				}
 
 				g_Map.setHeight(