OpenGL 2.0 introduced the concept of programmable pipeline. The graphics pipeline was composed of these steps: Thus, the effects and operations that could be applied were limited by the API itself (for instance, “set fog” or “add light”, but the implementation of those functions were fixed and could not be changed). The programmer was constrained to the set of functions available for each step. This model employed a set of steps in the rendering process which defined a fixed set of operations. First versions of OpenGL employed a model which was called fixed-function pipeline. The sequence of steps that ends up drawing a 3D representation into your 2D screen is called the graphics pipeline. Modern OpenGL lets you think in one problem at a time and it lets you organize your code and processes in a more logical way. It is actually simpler and much more flexible. Let me give you an advice for those of you that think that way. You may end up thinking that drawing a simple shape to the screen should not require so many concepts and lines of code. If you are used to older versions of OpenGL, that is fixed-function pipeline, you may end this chapter wondering why it needs to be so complex. In this chapter we will learn the processes that takes place while rendering a scene using OpenGL.
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