def __init__(self, filename=None):
        self.filename = None
        if filename:
            self.load(filename)
def mouse_rotate(xAngle, yAngle, zAngle):
    glRotatef(xAngle, 1.0, 0.0, 0.0);
    glRotatef(yAngle, 0.0, 1.0, 0.0);
    glRotatef(zAngle, 0.0, 0.0, 1.0);