it is done

core/src/mindustry/world/Edges.java

@@ -0,0 +1,80 @@
+package mindustry.world;
+
+import arc.math.Mathf;
+import arc.math.geom.*;
+
+import java.util.Arrays;
+
+import static mindustry.Vars.world;
+
+public class Edges{
+    private static final int maxSize = 11;
+    private static final int maxRadius = 12;
+    private static Point2[][] edges = new Point2[maxSize][0];
+    private static Point2[][] edgeInside = new Point2[maxSize][0];
+    private static Vector2[][] polygons = new Vector2[maxRadius * 2][0];
+
+    static{
+        for(int i = 0; i < maxRadius * 2; i++){
+            polygons[i] = Geometry.pixelCircle((i + 1) / 2f);
+        }
+
+        for(int i = 0; i < maxSize; i++){
+            int bot = -(int)(i / 2f) - 1;
+            int top = (int)(i / 2f + 0.5f) + 1;
+            edges[i] = new Point2[(i + 1) * 4];
+
+            int idx = 0;
+
+            for(int j = 0; j < i + 1; j++){
+                //bottom
+                edges[i][idx++] = new Point2(bot + 1 + j, bot);
+                //top
+                edges[i][idx++] = new Point2(bot + 1 + j, top);
+                //left
+                edges[i][idx++] = new Point2(bot, bot + j + 1);
+                //right
+                edges[i][idx++] = new Point2(top, bot + j + 1);
+            }
+
+            Arrays.sort(edges[i], (e1, e2) -> Float.compare(Mathf.angle(e1.x, e1.y), Mathf.angle(e2.x, e2.y)));
+
+            edgeInside[i] = new Point2[edges[i].length];
+
+            for(int j = 0; j < edges[i].length; j++){
+                Point2 point = edges[i][j];
+                edgeInside[i][j] = new Point2(Mathf.clamp(point.x, -(int)((i) / 2f), (int)(i / 2f + 0.5f)),
+                Mathf.clamp(point.y, -(int)((i) / 2f), (int)(i / 2f + 0.5f)));
+            }
+        }
+    }
+
+    public static Tile getFacingEdge(Tile tile, Tile other){
+        return getFacingEdge(tile.block, tile.x, tile.y, other);
+    }
+
+    public static Tile getFacingEdge(Block block, int tilex, int tiley, Tile other){
+        if(!block.isMultiblock()) return world.tile(tilex, tiley);
+        int size = block.size;
+        return world.tile(tilex + Mathf.clamp(other.x - tilex, -(size - 1) / 2, (size / 2)),
+         tiley + Mathf.clamp(other.y - tiley, -(size - 1) / 2, (size / 2)));
+    }
+
+    public static Vector2[] getPixelPolygon(float radius){
+        if(radius < 1 || radius > maxRadius)
+            throw new RuntimeException("Polygon size must be between 1 and " + maxRadius);
+        return polygons[(int)(radius * 2) - 1];
+    }
+
+    public static Point2[] getEdges(int size){
+        if(size < 0 || size > maxSize) throw new RuntimeException("Block size must be between 0 and " + maxSize);
+
+        return edges[size - 1];
+    }
+
+    public static Point2[] getInsideEdges(int size){
+        if(size < 0 || size > maxSize) throw new RuntimeException("Block size must be between 0 and " + maxSize);
+
+        return edgeInside[size - 1];
+    }
+}