新增 circleCollider与 polygonCollider

source/src/Physics/Shapes/Circle.ts

@@ -1,7 +1,7 @@
 ///<reference path="./Shape.ts" />
 class Circle extends Shape {
     public radius: number;
-    private _originalRadius: number;
+    public _originalRadius: number;
     public center = new Vector2();
 
     constructor(radius: number) {

source/src/Physics/Shapes/Polygon.ts

@@ -93,6 +93,10 @@ class Polygon extends Shape {
         throw new Error(`overlaps of Pologon to ${other} are not supported`);
     }
 
+    /**
+     * 找到多边形的中心。注意，这对于正则多边形是准确的。不规则多边形没有中心。
+     * @param points 
+     */
     public static findPolygonCenter(points: Vector2[]) {
         let x = 0, y = 0;
 
@@ -104,6 +108,16 @@ class Polygon extends Shape {
         return new Vector2(x / points.length, y / points.length);
     }
 
+    /**
+     * 重定位多边形的点
+     * @param points 
+     */
+    public static recenterPolygonVerts(points: Vector2[]){
+        let center = this.findPolygonCenter(points);
+        for (let i = 0; i < points.length; i ++)
+            points[i] = Vector2.subtract(points[i], center);
+    }
+
     /**
      * 迭代多边形的所有边，并得到任意边上离点最近的点。
      * 通过最近点的平方距离和它所在的边的法线返回。