I'm a little stumped on getting worldspace transforms from a rivet, for purposes of driving a Vellum sim. I'm importing FBX animation and using Rivet to get a point group for transforms, I need to set my initial transform to that group as a parent, and then run the sim based on that point motion. Any advice on this is much appreciates

If I understand correctly, you could parent your geometry to your rivet, then re-import it in an unparented node using Tranform: “Into This Object” for the Vellum sim.

That should work, but my vellum sim goes nuts even if I drop a timeshift to remove motion. I'm targeting the motion as a SOP path in the solver. Its got to be a vellum targeting thing

Solved. Apparently you can't target as a SOP path in the Vellum solver if you're bringing motion in this way, but it does work if you target it as the first input