So having seen the nice tip about using a still frame from a video clop onto which particles from PI will be comped over, it occurred to me that that could possibly work with MULTIPLE frames from a video clip, since PI can use “animated” sprites.
So I took a random old 24fps B&W cartoon .mp4 and converted it (in Natron, but it’d work with anything else) to a sequence of .jpg files. The video clip was about 3 seconds long, and I only rendered every 4th frame IIRC. The lower that number, the more frames of course. Also, I made the files only 480x270 (16:9) and 50% compression. Quality doesn’t really matter since it’s just a reference. MORE important is file size, for speed of playback. Crunch it down hard and harder, as long as you can still make it out well enough to place the particle system(s).
I DID also learn that PI really really wants file sequences to start with ###0 or ###1 … not something like, say, 3448 or152. No. Make sure the filenames start with, say, 000 or 001, and then follow up to your frame count.
I ended up with 24 files, and imported them as a custom shape. And then, of course, setting that particle and emitter up as normal for a still backplate. Except animated! \o/ WOOT
No slowdowns, no problems. Worked great. Could easily do it with more frames, and thus finer detail.
WOO HOO!! \o/