Imersite tanks rendering performance when stacked on a belt. Just an empty save with one zigzag belt of Imersite stacked on the belt and I have 41fps.

Steps to reproduce:
1. new game
2. pick sandbox
3. enable all technologies and cheats
4. put an infinity chest with imersite and a loader pointing away from it
5. drag a zig zag belt and end it with a loader pointing to a chest.
6. watch how your fps gets low.

I think other imersite things can cause this too.

i also have this issue
fps drops hard looking at imersite

Seems like there has been some improvements on this. It is not perfect but much better.

Imersite and tech cards emit lights that takes processing power.
Turning of occluded lighting in graphics options should fix it if it causes too much trouble.