OpenGL利用C语言做出4个不同的视口，每个视口中都有一个按不同方向旋转的带颜色的四棱锥，C语言代码完整，并标注完整注释，适合初学者参考学习。-OpenGL use C language to make four different viewport, each viewport has a according to the different direction of colored rectangular pyramid, C language code complete, full an