OpenGL Programming Guide

Chapter 3Viewing

Viewing and Modeling Transformations

As noted in "A Simple Example: Drawing a Cube," viewing and modeling transformations are inextricably related in OpenGL and are in fact combined into a single modelview matrix. One of the toughest problems newcomers to computer graphics face is understanding the effects of combined three-dimensional transformations. As you've already seen, there are alternative ways to think about transformations - do you want to move the camera in one direction, or move the object in the opposite direction? Each way of thinking about transformations has advantages and disadvantages, but in some cases one way more naturally matches the effect of the intended transformation. If you can find a natural approach for your particular application, it's easier to visualize the necessary transformations and then write the corresponding code to specify the matrix manipulations. The first part of this section discusses how to think about transformations; later, specific commands are presented. For now, we use only the matrix-manipulation commands you've already seen. Finally, keep in mind that you must call glMatrixMode() with GL_MODELVIEW as its argument prior to performing modeling or viewing transformations.

Thinking about Transformations
Modeling Transformations
Viewing Transformations

OpenGL Programming Guide