//Geometry pipeline Pseudo code
Mat4x4 ModelViewXForm, ProjectionXForm;
Plane ViewVolume[6];
Vector4 vertex,projectedVertex,clipVertex ;
for_each vertex
{
screenSpaceVertex =
viewportXForm *
perpectiveDivide(
clip(
(ModelViewXForm * ProjectionXForm * vertex),
ViewVolume)
)
);
}
Note: For more information look at gluProject(...) and Vertex Shader programs
