光照模型，1. 绘制OpenGL程序，显示一个圆环，点光源设在圆环的中心位置，通过键盘操作实现光源的移动，观察光源移动时圆环的显示效果-Illumination model, drawing OpenGL program, displays a ring, the movement of the point source located at the center position of the ring, to achieve a light source through the keyboa