WINDOW TO VIEW POINT TRANSFORMATION
some important terms:

Window-to-View port mapping is the process of mapping or transforming a two-dimensional, world-coordinate scene to device coordinates. In particular, objects inside the world or clipping window are mapped to the view-port.
The view port is displayed in the interface window on the screen. In other words, the clipping window is used to select the part of the scene that is to be displayed. The view-port then positions the scene on the output device.
This mapping of coordinate is achived with the use of coordinate transformation which is known as viewing transformation.
This process is performed by the following transformation :

1. Normalized transformation (N)
2. workstation transformation (W)

formula is used: Viewing transformation = normalized transformation . workstation transformation i.e;      
                                        V = N * W