You really will need to use blueprint to make this interactive. Hook up a material parameter called "Wet" or whatever you like. I'd suggest a 0-1 range, where 0 is dry, 1 is fully wet, then drive your transition between wet and dry with that parameter. (lerp node, if node, whatever more complicated setup you like) In…
Hey! I'm not a master in UE4 but have some experience and, as far as I know, this could be done using vertex painting to switch between textures. That will solve the transition between dry and wet but, to make it happen or make some surface able to trigger the change you'll need to use blueprints or coding and that's not…