kill points across time?

[ingersoll]

Is there a way to blast things across time?

Short scenario: I have a set of points, and some of them behave badly some of the time. It's easy to set an attribute on the bad points and kill them, but I don't want the pointcount to vary across time. I have an ID on the points. I would like to be able to check if a point is ever bad, and then kill it at frame 1 - so my output has a constant pointcount with constant IDs of only the points that are never bad.

Possible? How?

Long story: I'm using a FLIP sim to make points wander nicely across a surface. The bulk motion is great, but the border points behave terribly. I can't delete the border points during the sim, because I lose fluid volume and all my points wander off the edge. Most of the border points stay at the edge of the sim, and it's easy to transfer an attribute to them post-sim and kill them off -- but there are exceptions. Some "good" points wander to the edge and get stuck; some "bad" points work their way off the edge and join the bulk motion. If I'm just blasting the border points as a post process, those few points that escape end up ruining my pointcount. How do I smite them?

Thanks in advance!

[ryew]

Check out a Solver SOP to create a group that is persistent across time, then delete the offending points post-sim.  Matt Estela's excellent CGWiki covers using it pretty extensively: https://www.tokeru.com/cgwiki/index.php?title=The_solver_sop

[ingersoll]

Thanks, @ryew, it works well enough. Solver sop to accumulate the "bad" attribute, then timeshift to check attribute by ID at $FEND. Are you now, or will you ever have been... and it works!

 

[ryew]

Great, glad to hear it helped!