Can I use DistanceToNearestSurface with Forward Shading?

Hi,

I’m trying to make a mesh intersection effect with this not but I can’t get it to show up.
Is it because I’m using forward shading mode?

Cheers

EDIT: I see that I need to enable the fields in the project settings, and that they pre-calculate.
Probably not an effect I want to use then as I need it to work against moving characters.