| ?/TD> |
| Microsoft DirectX 9.0 |
A sampler register is an input register for a vertex shader, which is used to identify the sampling stage. There are four vertex shader sampling stage registers: s0 to s3. Four texture surfaces can be read in a single shader pass.
| Vertex shader versions | 1_1 | 2_0 | 2_sw | 2_x | 3_0 | 3_sw |
|---|---|---|---|---|---|---|
| Sampler register | x | x |
A sampling unit corresponds to the texture sampling stage, encapsulating the sampling-specific state provided by IDirect3DDevice9::SetSamplerState. Each sampler uniquely identifies a single texture surface, which is set to the corresponding sampler using the IDirect3DDevice9::SetTexture. However, the same texture surface can be set at multiple samplers.
At draw time, a texture cannot be simultaneously set as a render target and a texture at a stage.
Because there are four samplers, up to four texture surfaces can be read from in a single shader pass. A sampler register might appear only as an argument in the texture load instruction: texldl.
In vs_3_0, if a sampler is used, it needs to be declared at the beginning of the shader program using the dcl_textureType instruction.