[每日Shader]DirectX.9.Programmable.Graphics.Pipeline[一]

Virtual Machine Block Diagram

1.     Each register contains four floating-point values.

2.    ■ Input registers read from the vertex buffer

■ Constant registers provide constants to the ALU

■ Temporary registers are like temporary shader variables

■ Output registers contain the shader results

Shader Layout

    ■ A version instruction

■ Comments

■ Constants

■ Input register declarations

■ Instructions

Sample:

 

 

1.    A version instruction must be the first instruction in any shader.

2.    Constants can be assembled into shader code with the def instruction.

These constants are read-only by the shader.

3.    Each register can hold up to four values.

4.    Vertex shader input registers are different from constant registers

in that they need to be declared before they're used. The declaration

is required because it binds a shader input register with its corresponding

vertex buffer component. When the vertex shader runs, the vertex buffer data

is streamed into the vertex shader input register named in the input register

declaration.

5.    Instruction types: flow-control, arithmetic, texture, and macro-ops.

6.    Every vertex shader must write to the position register, or it will fail validation

when it's assembled. The only exception is when an application calls

ProcessVertices to apply a vertex shader to a set of vertices, and return the

results in a vertex buffer. In this case, no rendering is done.