Convenience function to make a vector out of two points.

git-svn-id: svn+ssh://src.earth.threerings.net/nenya/trunk@415 ed5b42cb-e716-0410-a449-f6a68f950b19

src/as/com/threerings/flash/Vector2.as

@@ -44,6 +44,14 @@ public class Vector2
         return new Vector2(p.x, p.y);
     }
 
+    /**
+     * Creates a new Vector2 pointing from s to t.
+     */
+    public static function fromPoints (s :Point, t :Point) :Vector2
+    {
+        return new Vector2(t.x - s.x, t.y - s.y);
+    }
+    
     /**
      * Creates a Vector2 of magnitude 'len' that has been rotated about the origin by 'radians'.
      */