How to control rotation in RBD sims?

[Pancho]

I managed in Softimage to achieve some results a few years back, but now in Houdini I wonder how to do this.

I guess there are several scenarios.

One would be to add a rotation force as soon as an explosion force (e.g. magnet force with negative values) is altering the packed geometry to make the flying pieces look more interesting. If they don't hit each other early in the explosion, they tend to fly in a rather linear manner without rotating around themselves.

Another purpose of controlling the rotation would be to have something like a goal rotation for the object. A force which tries to achieve a certain orientation if possible or align the particles in a certain manner to a collision or attration geometry.

Can anybody point me to some solutions? RBD and rotation only spits out one hit with the search engine.

Cheers

Tom

[Jordan Walsh]

You can import a w attribute the same way as a v attrib. This is angular velocity that you can set in sops how ever you want. You can modify it in a sop solver or use a torque node to add rotational force. You can also set the orient attrib to set the inital rotation on the objects.

[Pancho]

Mmmh. I took a look at the Torque Force, but it seems to be a pop force. As soon as I connect it to my Autodopnetwork I get an error message that it is the wrong kind of connection.

If I would set w on my packed primitives by using an attribute create, how would I use it as a force which initially give my object a spin and/or use it as an orientation force which the object wants to reach, something like the magnetforce for position?

[Navneet Arora]

you can update w attribute every frame or just on the intial frame of simulation so it will act as an initial force. add w attribute to override attrib in packed geo options

[windwolfx23]

how to rebuild a demolished building?how to accurately put simulated fragments back to its original position and rotation. 

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