Hi,

I started learning DOP's recently. I have a doubt about collisions. I created a simple “rbdGluedObject” and made it fall from a certain height on to a ground plane, using gravity & rbdSolver . When the object touches the ground, it breaks into pieces, which is what i want. But the problem is, it is inter-penetrating the ground plane. In the collisions tab of the rbdObject, i chose the surface penetration type as “edges”. Also after the object falls down on the ground, it keeps vibrating like crazy as well as penetrating the ground. Can someone tell me why this is happening ?

Thanks,
Sanjay

PS : I was practicing all these stuff at work, where we use houdini 10. I see this problem happening only with houdini 10. I did the same thing with houdini 9.5 apprentice version from home. It works perfectly.

If there are any interpenetrations, the first place you want to look at is the collision geometry itself. Look at the collisons tab of the glueobject, and turn on display collision geometry. Go into wireframe (or turn off display geometry in the glueobject) and look at the volume collision surface. If there are any holes in it, up the divisions until you have something that works well.

As for the vibrating like crazy thing. Add a RBDAutofreezeDOP at the end of the node chain, (also you might want to play around with a dragDOP as well). Default settings should be fine, although this will be scene/scale dependant. This DOP, has a threshold, once that is passed, the objects in question are removed from the simulation.

Hi,
I've attached a hip file which has a simple simulation. I made sure there are no holes in the volume collision surface, of the rbd object. Also i added a rbdAutoFreeze Sop, but it dint fix my issue. Can you please check the file ?

Thanks,
Sanjay

I see where your problem lies. The natural value for gravity is around -9.8, and you have the gravity node set to -980.665. Changing this to -9.8 solves the shaking and popping of the boxes. Then the surface representaion set to edges stops the interpenetration.

Cheers.

Thanks a lot for ur help!!

Cheers,
Sanjay