tex1D (HLSL reference) - Select the mip level
Samples a 1D texture using a gradient to select the mip level.
| ret tex1D(s, t, ddx, ddy) |
|---|
Parameters
| Item | Description |
|---|---|
| s |
[in] The sampler state. |
| t |
[in] The texture coordinate. |
| ddx |
[in] Rate of change of the surface geometry in the x direction. |
| ddy |
[in] Rate of change of the surface geometry in the y direction. |
Return Value
The value of the texture data.
Type Description
| Name | In/Out | Template Type | Component Type | Size |
|---|---|---|---|---|
| s | in | object | sampler1D | 1 |
| t | in | vector | float | 1 |
| ddx | in | vector | float | 1 |
| ddy | in | vector | float | 1 |
| ret | out | vector | float | 4 |
Minimum Shader Model
This function is supported in the following shader models.
| Shader Model | Supported |
|---|---|
| Shader Model 4 | yes (pixel shader only) |
| Shader Model 3 (DirectX HLSL) | yes (pixel shader only) |
| Shader Model 2 (DirectX HLSL) | yes (pixel shader only) |
| Shader Model 1 (DirectX HLSL) | no |
- Significant code reordering is done to move gradient computations outside of flow control.
- If the D3DPSHADERCAPS2_0 cap is set with D3DD3DPSHADERCAPS2_0_GRADIENTINSTRUCTIONS, the compiler maps this function to texldd.
Remarks
When flow control is present in a shader, the result of a gradient calculation requested inside a given branch path is ambiguous when adjacent pixels may go down separate flow control paths. Therefore, it is deemed illegal to use any pixel shader operation that requests a gradient calculation to occur at a location that is inside a flow control construct which could vary across pixels for a given primitive being rasterized. If either side of an if statement with the branch attribute uses a gradient function a compiler error may be generated. See if Statement (DirectX HLSL).