The common transformation process for producing the desired view is analogous to taking a photograph with a camera. As shown in Figure 5.1 the steps with a camera (or a computer) might be the following:
1. Move your camera to the location you want to shoot from and point the camera the desired direction (viewing transformation).
2. Move the subject to be photographed into the desired location in the scene (modeling transformation).
3. Choose a camera lens or adjust the zoom (projection transformation).
4. Take the picture (apply the transformations).
5. Stretch ...