Real-Time Shader Programming
An indispensable reference for the game developer, graphics programmer, game artist, or visualization programmer, to create countless real-time 3D effects.
TABLE OF CONTENTS Real-Time Shader Programming
TEMPORARY REGISTERS
r[n]: The Temporary Registers
The temporary registers can be used to hold anything you want in a pixel shader.
Temporary registers are considered uninitialized when a vertex shader is first loaded, and an attempt to assemble a shader that fails to initialize a temporary register before using it will fail validation (Table 8.6).
| PS VERSION | 1.0 | 1.1 | 1.2 | 1.3 | 1.4 | 2.0 |
|---|---|---|---|---|---|---|
| NUMBER | 2 | 2 | 2 | 2 | 6 | 12 |
| PORT LIMITS | 2 | 2 | 3 | 3 | 3 | 3 |
| READ/WRITE? | RW | RW | RW | RW | RW | RW |
| RANGE | Max | Max | Max | Max | Max | 16- or 32- |
| Pixel- | Pixel- | Pixel- | Pixel- | Pixel- | bit float | |
| Shader | Shader | Shader | Shader | Shader | precision | |
| Value | Value | Value | Value | Value |
The r0 register is a special case, and all pixel shaders except PS 2.0 must write r0 as the final color of the pixel that is being rendered. PS 2.0 has added specific output registers.
The r5. r and .g register elements are used as output if you used the texdepth instruction.
| Note | Since texture registers are read/write (except in PS 1.0, 1.4, and PS 2.0), you are free to use unused (or no longer needed) texture coordinate registers as extra temporary registers. |
s[n]: The Texture Sampling Stage Registers
 | The DirectX 9 pixel shader 2.0 model separated the texture registers into texture coordinate registers and texture sample stage registers. A sampling stage register identifies a sampling unit that can be used in... |
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