My final point is not exactly wet clothes, but I can’t explain that. I want to know how to change to different channel of texture on specific part of the mesh in real time like when you enter in water? And can it be done with transition like when you are working in the engine and not just instant slap between the channels?
if your pants have a proper UV and texture, you just create a mask and apply whatever roughness/specularity/albedo you see fit Onto that mask.
you can make the mask fade out over time as well, but you should probably do that with blueptint rather then the material.
usually you use a render target or something similar IF you can afford the cost of figuring out how to render it.
if you can’t, then you use pre-baked textures.
for wet clothes uou could potentially use the object size to determine how high the wet texture needs to fade, for instance. Saving you from having to use render targets and such.