Pro OpenGL ES for iOS

CHAPTER 1: Computer Graphics: From Then to Now (^29)
Finally, we are done with the very first example. Yes, for the 3D newcomers out there, it
was likely too much information too soon. But I have a theory that if the first thing you do
in the morning is to eat a cold frog, the rest of the day is bound to be much better.
Consider this first example a cold frog, at least until Chapter 7 that is.

OpenGL Architecture

Now since we’ve analyzed to death a ‘‘simple’’ OpenGL program, let’s take a brief look
at what goes on under the hood at the graphics pipeline.

The term pipeline is commonly used to illustrate how a tightly bound sequence of events
relate to each other, as illustrated in Figure 1-12. In the case of OpenGL ES, the process
accepts a bunch of numbers in one end and outputs something really cool-looking at
the other end, be it an image of the planet Saturn or the results of an MRI.

OpenGL application Geometry and texture

Vertex data Lighting, transform, scale, etc

3D Geometry Clipping

Fog and texture

Fragment

Framebuffer Stencil, alpha, z-tests, blending

Eyeballs “Hey, that’s really cool!”

Projection

Rasterization

“2D” Geometry

Per-fragment operations

Figure 1-12. Basic overview of the OpenGL ES 1.x pipeline