Graphic Details

Hello!

If I want to add graphic levels (low, medium, high) to my game, how should I do it? I have to create a low, a medium, and a high version for each model?

That is an optimization that you might want to consider if you need to squeeze out that last bit of performance - however I don't believe it is necessary.

Unity comes with Build Quality Settings you can set up. They are found in Edit>Project Settings>Quality and there are actually 6 quality levels you have to configure. They primarily deal with the way dynamic lights & shadows are drawn, but also texture quality and anti alias.

From there you need to set up a menu and a way for the user to switch between them. I will not take the time to explain the code involved but see the above linked page and read up on the scripting attached.

Hope that helps.

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Graphic levels usually refers to the amount of textures used ( vram), the complexity of the shaders rendering the scene and stuff like shadows, number of pixel lights, AA etc. In which case EqualsEquals answer is all you need.

Its very rare, if ever that you provide distinct resolutions for models. Most of the time a single high quality model is used and will be dynamically LOD in the scene if polygon count is an issue. Not sure if Unity supports that though, in which case providing distinct resolutions may be beneficial, but I highly doubt you'd need to, as its a pretty specialised requirement.