Hello, as an indie developer, I'm working on my first self-publishing game. I'm using unity. It's a valet simulation game but I want to create a side task such as cleaning. I don't have game artists. I want to dirty and clean car model, but I can't change the material of my car model, so I can't use different shaders. How can I make my car dirty and clean?

Is there anyone can help or suggest any solution?

simulatorgames said:
I want to dirty and clean car model, but I can't change the material of my car model, so I can't use different shaders.

Nonsense. You load textures from images, so you can load different textures for the “same” 3D model from different images (dirty and clean).

Your shaders can be the same for both cases: special textures (e.g. mud splash opacity, hue and roughness) can provide a representation of the dirt as a deviation from the appearance of the clean car (e.g. locations with mud will override the car's paint colour with grey/brown, and they will have almost no specular highlights).

@LorenzoGatti many thanks your help!

I'm using asset store, I don't have game artist. That's why I don't know the UV map about that. It has shader material without the texture. So how can I make that car look dirty and clean? It would be great if I can handle this.

A dirty car matching the clean car doesn't seem something you can obtain ready made from an asset store, but you might also be overestimating the artistic and technical competence needed to paint dirt on the car.

Can you replace textures and/or shaders in the car asset you have? You say you can't, but there can be tools and methods you haven't tried, particularly conversion/extraction to file formats that can be edited and then imported back into Unity.

And don't lose sight of the objective: cleaning cars seems likely to have a lower player fun/developer effort ratio than other game activities.
For example, challenges about parking itself (obstruction puzzles, time constraints, narrow spaces, traffic etc.) don't require special assets, just a variety of other cars and the parking lot you should already have.