定义两个视口，分别显示两个不同颜色的三角形，其中一个视区定义在显示窗口的左半区，显示蓝色三角形，另一个视区定义在右半区，显示红色三角形。同时在显示红色三角形时加了一个旋转变换。(Two viewports are defined to display two triangles of different colors, one of which is defined in the left half of the display window, showing a blue triangle, and the other in the right half, showing a red triangle. At the same time, a rotation transformation is added when displaying the red triangle.)