[Sidefx-houdini-list] Rotate only between two angles in DOPs?

Craig Zerouni craig at sidefx.com
Thu Nov 23 13:15:51 EST 2006

Peter -

You need two RBD Constraints to hold the door in place, and then an RBD 
Rotation Constraint to constrain the rotation itself. In the 
Relationship tab of the Rotation Constraint, set the Type to Spring, and 
make the Spring Strength a big number (experiment with the definition of 
"big" - it will depend on the size and density of your object).

That should be it.

You can't mail hip files to the list, but if you want, I can send you an 
example file.


Peter Bowmar wrote:
> Hello,
>      I've spent some considerable amount of time on this and can't
> find an answer. Basically, I want to constrain the rotation of an RBD
> object's angle. I have constrained the rotation (think of a door being
> hit by a ball) let's say to the Y axis, and that works fine, but when
> hit by the ball it swings freely.
>     In a tutorial or demo, "blocks" were used to prevent the door
> swinging beyond the angles desired. This will not work in my case, the
> impulses are more complex, and the blocks don't work. I need to be
> able to explicitly control the angles of swinging. In an ideal world,
> using a spring system so it's not a "hard" constraint on the angle.
>     Unless I'm missing something, I'll have to use modify data or
> somesuch to alter the actual "orient" data using Hscript etc. This
> seems like overkill for something that should be a pretty common
> operation in an RBD sim. Hopefully I'm missing something and someone
> will cleverly point this out, making me feel shame, yet happiness that
> I can accomplish my goal.
> Cheers,
> Peter B
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