Try messing with the thread count by un-ticking auto detect threads, going for negative numbers and you'll see some sort of massive pixel thing in the ipr as you navigate that gradually disappears as it cleans up, at first I thought it was caused by the the bucket size, but I'm not too sure if it's also a variable
C4DtoA 3.2.1
C4D R21.207
Thread count is for leaving threads free for CINEMA 4D, so it won't make IPR more interactive.
IPR is a series of renders with increasing AA values, so there's always a "massive pixel thing in the ipr" for the first pass.
I would turn on logging and check the Arnold log for an IPR session.
Yeah but after putting it back to default, everything in default it would still do the same thing.
Okay been playing around with it more, noticed it was caused by the texture. Previous versions though I didn't have any problem with 8k and up, I don't know why I'm just experiencing this now. It doesn't happen on a new scene btw, tried it, but I can't really show it off on video since the recorder is pretty heavy.
Make sure you are using TX textures, which load much faster than non-tx textures (e.g. auto Tx generation is enabled in the render settings or generate tx files manually via the Tx Manager).
I also noticed in your video, that the initial sampling level is set to -10. Is that really necessary? Usually the default -3 or -4 should work fine.