3D viewing pipeline

The 3D viewing pipeline is the sequence of transformations that converts a 3D scene described in object coordinates into a 2D image on the display device.

 Modeling        Modeling
 Coordinates --> Transform --> World Coordinates
                                     |
                              Viewing Transform
                                     v
                             Viewing Coordinates
                                     |
                             Projection Transform
                                     v
                            Projection Coordinates
                                     |
                         Normalization + Clipping
                                     v
                           Normalized Coordinates
                                     |
                           Workstation Transform
                                     v
                             Device Coordinates

Stages:

1. Modeling transformation: each object is built in its own local (modeling) coordinates and placed into the common world coordinate system using translation, rotation and scaling.
2. Viewing transformation: the world is re-expressed in a coordinate system attached to the camera (view reference point, view-plane normal N and view-up vector V). It is done by translating the view reference point to the origin and rotating so that N lies along the z-axis.
3. Projection transformation: 3D viewing coordinates are projected onto the view plane, by parallel or perspective projection, giving 2D coordinates.
4. Normalization and clipping: coordinates are mapped to a normalized view volume (0 to 1 or −1 to 1) and parts of the scene outside the view volume are clipped away.
5. Workstation (viewport) transformation: the normalized coordinates are mapped to the viewport of the display device, giving device (pixel) coordinates for scan conversion.