说明：  本程序提供了三维坐标转换为二维坐标的算法，实现在屏幕上画三维图，并提供立方体绕任意轴旋转动画的算法。
(procedures for the three-dimensional coordinates of the conversion of two-dimensional coordinates of the algorithm to achieve on the screen painting three-dimensional map, and provide cube rotating animation algorithms.)