说明：  opengl纹理映射绘制场景，给出顶点的纹理坐标和几何坐标 在绘制纹理映射场景时，不仅要给每个顶点定义几何坐标， 而且也要定义纹理坐标。经过多种变换后，几何坐标决定顶点在屏幕 上绘制的位置，而纹理坐标决定纹理图像中的哪一个纹素赋予该顶点
(texture mapping opengl rendering scenes given vertex texture coordinates and geometric coordinates in the texture mapping rendering scenes, not only to give the definition of the geometric coordinates of each vertex, but also the definition of texture coordinates. After a variety of transformation, the geometric coordinates of vertices on the screen decided to draw the location where the texture image Texture coordinates decide which one gives the Su-Wen vertex)