# DDXY Node


![](../img/ddxy.png)

### Description

This node outputs the sum of both partial derivatives of the specified input value with respect to the screen space x-coordinate and screen-space y-coordinate respectively. This node can only be used in the pixel shader stage.


> **Notice:** For more information on how the derivatives are calculated please follow [this link](http://www.aclockworkberry.com/shader-derivative-functions/).