After about 8 hours (!!) i finally figured this one out, including how to get the sphere to accumulate other objects on top of ones it has already stuck to. the solution i came up uses a script solver to deal with the impact data and decide which object to glue something to. simply put, i'm storing the objects impact "otherobjid" field, so long as it isn't the ground plane (easy since that is ID 0 in my net), and then i'm setting the glue object field in an rbd state object with: `dopobjectlist($DOPNET, dopoption($DOPNET, $OBJID, "AuxImpacts", "firstImpactID"), 1)` where AuxImpacts and firstImpactID are my custom names. i tried using chops for this, but couldn't figure out how to preserve the data from the dynamics chop, as the impact data exists only for one frame. i suspect this might be possible, but i just don't know how to wrangle data in chops well enough yet. is there another way to do this? anyway, i learned a lot doing this challenge... thanks!