Get Mud Off of Object

Hi there
If you can imagine a game where you need to hand wash an object, like a shoe, or dish or window and this object has mud, or dirt, some caked on, some more fluid etc,...

a) how would you “paint” this object in a random coating pattern of mud and dirt etc? Would you use shaders or actual model objects?
b) and how would you “wash it” off?

Image shown is an example of something I like but not particularly exactly what I am going for.

Anyhow,
Thank you

 

I haven't personally done this, but I think a reasonable approach would be the following:

• Create a procedural map, starting off all white, to represent the dirt. Call it a dirt map. Have the shader use the dirt map to apply the actual dirt texture to the UV coordinates indicated in the dirt map.
• Use RaycastHit.textureCoord to determine the coordinates of the part being cleaned, and set those pixels to black in the dirt map.

Seems reasonably simple, but again, I haven't tested it. Probably a bit more complex when you're dealing with sub-objects, or multiple renderers.

 

I think something like this would work for you: