Begins a new relative transform block. If you want to use relative transforms, you must use this method call and the corresponding endTransform() method call prior to all setTransform() and draw() calls that make up a local object. beginTransform()...endTransform() blocks may be nested as needed.
Technically this method pushes the current OpenGL ModelView matrix stack down by one, duplicating the current matrix. That is, after this method call, the matrix on the top of the stack is identical to the one below it.