视口（ViewPort）是计算机图形学里面的重要概念之一。

计算机图形学的目的就是将三维空间的物体转换为二维图像，这是因为电脑的屏幕是个平面。然而，当决定哪些是需要绘制于电脑屏幕上的物体时，需要在三维坐标下思考。人们常犯的一个共同的错误：创建三维图形时就开始过早的思考最终的显示在二维屏幕上面的图像。

A viewport is a polygon viewing region in computer graphics.

In computer graphics theory, there are two region-like notions of relevance when rendering some objects to an image. In textbook terminology, the world coordinate window is the area of interest (meaning what the user wants to visualize) in some application-specific coordinates, e.g. miles, centimeters etc.