建立二维投影（以glOrtho函数）实例工程，通过修改参数，验证二维窗口到视口影射关系，以及裁剪效果，包括点裁剪、线裁剪、面裁剪和字体裁剪等效果。-The establishment of two-dimensional projection (to glOrtho function) examples of works by modifying the parameters of two-dimensional window to verify, as I insinuate, as well as the effect of cutting, including the point of cutting, line cutting, tailoring and font face, such as the effect of cutting.