Introduction to Pixel Shaders - Introduction to 3D Game Programming with DirectX 9.0 - page 318

Chapter 18
Introduction to Pixel
Shaders
A pixel shader is a program executed on the graphics card's GPU during
the rasterization process for each pixel. (Unlike vertex shaders,
Direct3D will not emulate pixel shader functionality in software.) It
essentially replaces the multitexturing stage of the fixed function pipe-
line and gives us the ability to manipulate individual pixels directly and
access the texture coordinate for each pixel. This direct access to pixels
and texture coordinates allows us to achieve a variety of special effects,
such as multitexturing, per pixel lighting, depth of field, cloud simula-
tion, fire simulation, and sophisticated shadowing techniques.
You can test the pixel shader version that your graphics card sup-
ports by checking the PixelShaderVersion member of the
D3DCAPS9 structure and the macro D3DPS_VERSION . The following
code snippet illustrates this:
// If the device's supported version is less than version 2.0
if( caps.PixelShaderVersion < D3DPS_VERSION(2, 0) )
// Then pixel shader version 2.0 is not supported on this device.
Objectives
To obtain a basic understanding of the concepts of multitexturing
To learn how to write, create, and use pixel shaders
To learn how to implement multitexturing using a pixel shader
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