missing polygon functions

lib/polygon.js

@@ -80,6 +80,10 @@ var cfactor,
     sfactor;
 
 function rotate(out, poly, radians) {
+    if (out.length > poly.length) {
+        out.splice(poly.length);
+    }
+
     len = poly.length - 1;
 
     cfactor = cos(radians);
@@ -98,6 +102,37 @@ function rotate(out, poly, radians) {
     return out;
 }
 
+function edges(out, poly) {
+    if (out.length > poly.length) {
+        out.splice(poly.length);
+    }
+
+    len = poly.length;
+    lens1 = len - 1;
+
+    // Calculate the edges/normals
+    for (i = 0; i < len; i++) {
+      Vec2.sub(out[i] = out[i] || [0, 0], poly[i < lens1 ? i + 1 : 0], poly[i]);
+    }
+
+    return out;
+}
+
+function normals(out, edges) {
+    if (out.length > poly.length) {
+        out.splice(poly.length);
+    }
+
+    len = edges.length - 1;
+    for (i = 0; i < len; i++) {
+        out[i] = out[i] || [0, 0];
+        Vec2.perp(out[i], e);
+        Vec2.normalize(out[i], out[i]);
+    }
+
+    return out;
+}
+
 var c_aux = [0, 0],
     c_aux2 = [0, 0];
 /**
@@ -130,6 +165,10 @@ var vec2_centroid = [0, 0];
  * @returns {Polygon}
  */
 function recenter(out, poly) {
+    if (out.length > poly.length) {
+        out.splice(poly.length);
+    }
+
     centroid(vec2_centroid, poly);
     var x = vec2_centroid[0],
         y = vec2_centroid[1];
@@ -170,6 +209,10 @@ function area(poly) {
 
 
 function transform(out, poly, m2d) {
+    if (out.length > poly.length) {
+        out.splice(poly.length);
+    }
+
     for (i = 0, len = poly.length; i < len; ++i) {
         Matrix23.transform(out[i] = out[i] || [], m2d, poly[i]);
     }
@@ -212,6 +255,10 @@ var Polygon = {
     //circumcenter: circumcenter,
     area: area,
     transform: transform,
+
+    normals: normals,
+    edges: edges,
+
     isVec2Inside: isVec2Inside,
 
     furthestPoint: furthestPoint,