Introducing OpenGL - C# Game Programming: For Serious Game Creation - page 22

The Pipeline
The pipeline flow is shown in Figure 2.3. This pipeline is known as the fixed
function pipeline. This means once the programmer has given the input to the
pipeline, all the functionality is set and cannot be modified—for instance, adding
a blue tint to the screen could easily be done at the pixel processing stage, but
in the fixed function pipeline the programmer has no direct control over this
stage.

Figure 2.3
The basic fixed function pipeline.

There are six main stages in the fixed function pipeline. Nearly all these stages
can be applied in parallel. Each vertex can pass through a particular stage at the
same time, provided the hardware supports it. This is what makes graphics cards
so much faster than CPU processing.

Input stage. This input is given in the form of vertices, and all the vertices'
properties including position, color, and texture data.

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Transform and lighting. The vertices are translated according to the cur-
rent view. This involves changing the vertex positions from 3D space, also
known as world space, to 2D space, also known as screen space. Some ver-
tices can be discarded at this stage if they are not going to affect the final
view. Lighting calculations may also be performed for each vertex.

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