title: OpenGl polygon rotation
body: <p>I'm trying to implement a moving and rotating polygon in OpenGl and C++.<br/>
  Movement and rotation are along the XZ plane(2D transformations only).<br/>
  The polygon is defined by a centre point and a set of vertices whose coordinates are stored as offsets from the centre point.<br/>
  The polygon is moved based on the user's key-press either in X or Z direction by simply adding the moved distance to the centre point and updating the vertices by adding the offset values to centre coordinates. <br/>
  Rotation with respect to centre point is implemented by using the glRotatef() function.<br/>
  But i need to know the coordinates of vertices for collision detection calculations.
  Is there any chance of just retrieving the vertex coordinates of the transformed polygon without performing matrix operations myself?</p>