The situation is that we paint water in the road mesh and want to add a splash effect when shooted,it that possible to apply a physical material for the vertex color area?thanks in advance.
there isn’t a way for such thing 
I requested this functionality 3 years ago, here: https://answers.unrealengine.com/que…-physmats.html
2 years ago it was accepted as a feature request but to this day there’s no news about it, and the ticket seems gone from the public tracker
its weird to walk in a water area with a asphalt physical material.can i simulate this in some other way?
the only way to do it is to use multiple materials on the mesh, so each material can have its own Physical Material