How large can a texture atlas be?

Let’s say I have an open world with 9 buildings (of course, the numbers of buildings in an open world is far more than 9) and each building has a 512x512 texture. If I am to combine these textures into an atlas, would it be a 1536x1536 texture? This texture atlas thingy’s got me really confused because atlases contain far more than 9 textures. Also is it possible/practical to put all textures in an open world into one atlas? Thanks.

Hello.

Yes, you could put all 9 textures in an atlas. The size would be 1536x1536.

A texture atlas contains however many textures are relevant…im not sure where you came up with they contain more then 9 textures (though sometimes they do, sometimes they dont).

Is it possible to put all the textures in an open world in an atlas? Certainly. Practical. No.
Read up on texture atlases with unity some, and you will see why it is not practical.