Perhaps you can generate a number of PQT noise fields in a webworker and then randomly pick one for each frame?

That would definitely help a bit! There's another limitation though: we have to update *every pixel* every frame, or the coherence in the noise gets lost. So it would still be quite choppy. I'll give it a go nevertheless, maybe it's not so bad in practice

You can create (and store) a new canvas from each tree in the main thread and apply it via drawImage(). Once a selection of frames has been rerendered this should then be even faster than Mike's white noise version. Prerendering should also be fairly fast if you use multiple workers.

Oh duh, that's so simple!

You might find https://observablehq.com/@fil/worker helpful (haven't used it myself yet, though)

I made a non-worker version for now, was quicker :)