2D vs 3D performance?

Unity Engine
1

I know there are a lot of variables regarding performance.

But if we think about having the underlying systems the exact same and the only differentiator is 2D or 3D in regards to visuals.

I also assume 3D physics are more expensive to calculate than 2D.

We also assume the game is like Factorio where a lot of calculations happen constantly taking up a lot of CPU time.

Would 2D outperform 3D?

What systems are there in 3D that would fight for the CPU vs 2D?

What systems are the bottlenecks when you scale up apart from physics?

A lot of games I played in 3D have never been able to have as many objects or players running as most 2D games I played. (Do not count MMOs into this because that is $$$).

If we also think about a 100 player dedicated multiplayer server.

Would a 2D game be able to perform better because of faster sprite rendering vs 100 player 3D models?

Will the server become less performant in 3D vs 2D? Logically it should not because it does not render anything right?

Anyone with some input and experience regarding this?

2

Does that mean that the gameplay is all 2D and only the visuals are 3D?

3

The computations behind the scenes are irrelevant to 2D/3D. It is just calculations.

If you look at Factorio for example all you do is put down conveyor belts, pipes, machine that convert one resource to another. This doesn’t matter if it is 3D or 2D since the machine itself is just calculating the progress.

It is not a lot of jumping around and advanced animations and cinematic sequences like an FPS.

The visuals I would imagine characters only have basic animations like running, interacting with objects and maybe shooitng bullets from a gun.