Scene Nodes - Fields based Selections

[tradition-shot]

I'm trying to learn Scene Nodes but I'm having trouble finding any information about how to use fields. Specifically I'd like to use a spline as a field to drive a polygon selection, but with nodes instead of with a selection tag set to fields like you'd normally do.

Are there any tutorials or resources that would show how to do this or does anyone here know how this can be done? Maybe there's a simpler solution that doesn't use fields at all?

Thanks