[Sidefx-houdini-list] DOPS: stuck inside a volume

Bill Watral bill at charlex.com
Wed Feb 8 11:49:16 EST 2006

I am creating a rigid body simulation of a lottery ball machine.  It is 
the type of machine that has paddles that rotate and stir the balls 
around a drum with some air blowing in to keep the balls floating around 
a bit.

Things are working pretty well in the sim but I have run into a problem 
I cannot figure out. The paddles collide with the balls and once in a 
while a ball will get stuck on the paddle. Once this happens it stays 
stuck to it and just rotates around the drum stuck there.

All collisions are laser scan ray intersect volume collisions. I have 
run through visualizing all the collision geo and it all looks closed 
and appears to have good topology. I am not using glue at all. My 
friction on all objects (static and dynamic) is 0.2 or lower. Bounce is 
set diff. per object  but is no more than 1 and is about .8 on most of 
the structure (the balls are the only things set at 1 for bounce). I 
have one gravity and one fan (blowing from below with some noise). The 
balls that do not get stuck fall nicely back down to the bottom, so I 
know it is not centripetal force keeping the balls pinned to the paddles.

Has anyone run into objects getting stuck inside volume collision objects?
Is there a setting to increase the force a volume applys to correct 


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