I work specifically with video game performance, mainly as a graphics programmer, and often focusing on getting things to work well across multiple platforms. I

I work specifically with video game performance, mainly as a graphics programmer, and often focusing on getting things to work well across multiple platforms. In my experience the performance issues are almost always a combination of how much is being simulated and rendered, how it's being rendered, and how much stuff is kept in memory at any given time. If you can improve culling before rendering and physics, minimize the surroundings streamed in to your immediate vicinity, and optimize some of the heaviest materials and post effects, that goes a really long way. Of course, there's an endless list of caveats depending on what your game specifically is, but even in an open world game where things happen off screen the above applies. You just have very simply LODs/imposters for faraway visuals and simplified logic running at lower frame rate for characters in other parts of the world.