Material optimization

I have 4 materials on model,
all 4 material have same shader,

Is there a need to make a common atlas for materials in one or does unity do it automatically?

 

Unity does not atlas them automatically, as far as I know. There are lots of different products on the asset store that provide this feature (I think there may be some free ones too). There are also free scripts floating around if you google it.

It's not too difficult to write a basic mesh combine/texture atlasing script using these two built-in functions:
https://docs.unity3d.com/ScriptReference/Mesh.CombineMeshes.html
https://docs.unity3d.com/ScriptReference/Texture2D.PackTextures.html
The tricky part is that you need to calculate new uv coordinates for the meshes so that they use the part of the atlas that contains their original texture.

Edit: two other things:
1) I think the step of combining meshes in a script may be unnecessary for static meshes because of Unity's static batching. I think it should automatically combine any static meshes with the same material

2)In addition to scripting, you could also use your 3D modeling software to atlas textures. 3D modelling software is generally better-suited for this type of thing anyway because it gives you an interface to control how the textures are packed.

 

Тhank you very much!