Weight map and gradients - controlling selection

Is there some way, maybe using nodes, of utilising a weight map to say place particles, but to control the placement not only based on the weight map, but the value within that weight map?

I’m thinking of an instance where you say have a ‘road’ painted onto a plane, so the road is weight 100% and the ‘open ground’ is 0%.
I wondered if you could place objects purely at the edge of the weight map, rather than all across it, so say using a gradient to apply a tight band of 5% to 25% of the gradient value for placement.

Or would it be a case of having to create an entirely separate vertex map for just the required points. I appreciate that would do it, but was wondering if there was some cool method of utilising an existing vertex / weight map. :slight_smile:

Moved from “General Forums > Blender and CG Discussions” to “Support > Particles and Physics Simulations”

Thanks, wasn’t exactly sure where to post it.