Affecting Performance

Hello. I just wanted to know what exactly affects the direct performance of a game. Lets say I want to create a landscape and far in the back ground (can’t actually go there) I have a giant mountain that I’m thinking about creating (almost 200k poly or so) and I’m wondering how it will affect the performance.

Also, even something more simple like lets say a rock that I placed half into the ground; will that bottom half of the rock which I cannot see affect the performance? does the game calculate every poly on the whole map simultaneously or does it just calculate what I can see on the screen? I’m just trying to create the game with at least some efficiency when running.

You are unlikely to get full answer withing just one post. There is so many things to consider, that it could easily take ap a hundred of pages.
However, your first steps should be here and here.

If you want more in depth look, I suggest searching for some books, that would cover basics of realtime 3d graphics.

Unreal engine have release a video that explain a little how performance thing happens, and how to optimize your game:

Also to answer your question:

Landscapes have their own system where they will be come lower res in the distance to save on performance.

Regular mesh will only render if they are on screen. If one polygon of a huge mesh is on screen, then the entire mesh will render, so make sure you split your meshed into smaller one, but not too small, because calling a lot of meshed will also decrease your performance.