Shader Basics  As mentioned before, both programmable pixel
shaders and programmable vertex shaders are items called for by
DirectX 8. You may recall from our GeForce3 Technology article
that both items work to change the graphics processor from a
fixed function processor to a programmable processor.  This is
done by producing pixel shaders and vertex shaders that are able
to compile and run low level code, much like a CPU does.
Previous generation video processors performed fixed function
transform and lighting calculations on vertex information and
fixed texturing, filtering, and blending operations on pixel
information. Since the operations were fixed, not only did new
features have to be implemented in an API in order to be used,
video processors had to be hard programed to perform these
operations. Programmable pixel and vertex shaders give a new way
of modifying vertex and pixel information by allowing a graphics
processor to manipulate this data without any loss of speed.
Vertex shaders are essentiall