Texture Atlas VS separate textures [A Game Performance Question]

D4N005H

Hello. Let's say we have a model with two textures assigned to it:

Now imagine this object is an apartment or a tree or something that will be copied several times in a scene and will be used in a game, Also the green texture will be used in some other object,Should this model use one texture 2D (which would be a texture atlas) OR should it use two separate texture 2Ds  as input (as shown in the above image)?  and why?

Obscura

Depends. In the case of a tree, I'd say use 2 materials, because then you can reduce the amount of transparency. In the case of the apartment building, probably I'd still go with multiple materials because it gives better control, and actually +-1 material doesn't make a big difference if its used properly, and if it has a reason. When I make building, I usually end up with multiple materials. The answer to your question also depends on some other things, like whats the target platform (well, this is something, that always determines how to approach things.). If its for mobile, then you need to optimize more, and then use atlas. If its console or pc then a few extra materials on something like a building is not a big deal nowadays. Although you should still keep it relatively optimized.

pixaeiro

Something else to keep in mind is the number of render calls. If you have one object with 3 textures sets (materials), then you'll have 3 render calls. If the object has one atlas texture set, then it's only one render call. Render calls happen in the CPU, so you want reduce the number of render calls.
Both types of models are valid and use widely..!

D4N005H

EDITED: After some research, and according to the info that you provided, I'll use separate textures for buildings.