Clip coordinates

The clip coordinate system is a homogeneous coordinate system in the graphics pipeline. In OpenGL, clip coordinates are positioned in the pipeline just after view coordinates and just before normalized device coordinates.

Objects are transformed via a projection transformation into clip coordinates, at which point it may be efficiently determined on an object-by-object basis which portions of the objects will be visible to the user. All coordinates may then be divided by the w component (the fourth component in homogeneous coordinates) in what is called the perspective division. This transformation puts the objects into normalized device coordinates.