def animate(self, frame_num):
    # print("Rendering frame %d..."%(frame_num))
    self.progress.update(frame_num)
    color = self.render_callback(frame_num)
    if self.ims is None:
        self.ims = plt.imshow(color, animated=True)
    else:
        self.ims.set_array(color)

    return self.ims,