# ddx

Returns the partial derivative of the specified value with respect to the screen-space x-coordinate.

ret ddx(x) |
---|

This function computes the partial derivative with respect to the screen-space x-coordinate. To compute the partial derivative with respect to the screen-space y-coordinate, use the **ddy** function.

This function is only supported in pixel shaders.

## Parameters

Item | Description |
---|---|

x |
[in] The specified value. |

## Return Value

The partial derivative of the *x* parameter.

## Type Description

Name | Template Type |
Component Type |
Size |
---|---|---|---|

x |
scalar, vector, or matrix |
float |
any |

ret |
same as input x |
float |
same dimension(s) as input x |

## Minimum Shader Model

This function is supported in the following shader models.

Shader Model | Supported |
---|---|

Shader Model 5 and higher shader models | yes |

Shader Model 4 | yes |

Shader Model 3 (DirectX HLSL) | yes |

Shader Model 2 (DirectX HLSL) | yes in ps_2_x; unsupported in ps_2_0. |

Shader Model 1 (DirectX HLSL) | no |

This function is supported in the following types of shaders:

Vertex | Hull | Domain | Geometry | Pixel | Compute |
---|---|---|---|---|---|

x |