def _blockUnderCursor(self, center=False):
        """
            returns a point in 3d space that was determined by
         reading the depth buffer value
        """
        try:
            GL.glReadBuffer(GL.GL_BACK)
        except Exception:
            logging.exception('Exception during glReadBuffer')
        ws = self.root.size
        if center:
            x, y = ws
            x //= 2
            y //= 2
        else:
            x, y = mouse.get_pos()
        if (x < 0 or y < 0 or x >= ws[0] or
                    y >= ws[1]):
            return 0, 0, 0

        y = ws[1] - y

        try:
            pixel = GL.glReadPixels(x, y, 1, 1, GL.GL_DEPTH_COMPONENT, GL.GL_FLOAT)
            newpoint = unproject(x, y, pixel[0])
        except Exception:
            return 0, 0, 0

        return newpoint

            returns a point in 3d space that was determined by
         reading the depth buffer value
        
viewports/camera.py