Is there a way to limit the amount of RAM and threads Corona uses while using interactive rendering? I find my mac pro gets really sluggish when Corona is calculating passes.
For RAM - you’d have to simplify the scene 
For threads, the info on adjusting how many threads it’s allowed to use is on the helpdesk page at https://help.c4d.corona-renderer.com/support/solutions/articles/12000035920-how-to-use-interactive-rendering-in-corona-renderer-for-cinema-4d-
Cheers!
Thanks, so how much RAM does Corona need? I have 64GB in my mac, but I still find interactivity really poor while the VFB is rendering.
RAM doesn’t affect the speed of rendering at all (until you run out of it). There will be an error warning from Corona if you are running low on RAM. I am not sure if you mean “interactivity of other software/the machine in general while IR is running” or “speed of IR itself” - in the first case, adjusting the number of threads given to IR can speed up the machine/other software, at the cost of IR itself being slower.
You never mentioned what hardware you are running on, the CPU will make a big difference to the second case, the speed of IR (as will the complexity of the scene).
here the corona ipr is pretty nice and smooth i must say in v5.
but we use dual xeons or threadripper 3 workstations, which give us pretty nice interactivity.
we also have “only” 64gb on each machines, so ram for sure isnt the problem, more the cpu i guess