Where to find it:

NodeGraph / Right Mouse Click / Add Nodes / Math / Extension Pack / D /

Partial derivatives of an input transformed into UV Space with an optional V Offset.

This is a stable-for-baking version of a screenspace dFdx, dFdY function call

Some things to keep in mind

•Due to the lookup in UV space, as opposed to window space, results differ from dFdx,dFdy - often for example giving less contrast

•If the operation is run on the result of an image operation (e.g. paint, bake points etc.) you might encounter artifactng as each pixel compared
to its neighbor will have a change in value.

•Offset V

Specifies the V Offset to apply, which can be used to rotate the effect.

Below is an example of taking the partial derivatives of a hemisphere shape, then rotating it by applying a uv offset.
In this case we are using the gl_dFd+UV Node which has both U and V Offset Options.

•F

Specifies the expression of which to take the partial derivative.

•Offset V
Allows feeding in the V Offset via a Node Input. If mapped the Offset V Option inside the Node are ignored.

•Output

Return the partial derivative transformed into UV Space, with a V Offset applied