OpenGL Programming Guide: The Official Guide to Learning OpenGL, Version 4.3, Eighth Edition

User Transformations

The stages of the rendering pipeline that transform three-dimensional coordinates for OpenGL viewing are shown in Figure 5.5. Essentially, they are the programmable stages appearing before rasterization. Because these stages are programmable, you have a lot of flexibility in the initial form of your coordinates and in how you transform them. However, you are constrained to end with the form the subsequent fixed (nonprogrammable) stages need. That is, we’ll need to make homogeneous coordinates that are ready for perspective division (also referred to as clip coordinates). What that means and how to do it are the subjects of the following sections.

Figure 5.5. Pipeline subset for user/shader part of transforming coordinates ...