[Sidefx-houdini-list] force rotation of a particle?

Andrew D Lyons tstexture at gmail.com
Fri Jul 30 00:24:48 EDT 2010


Alternately - do your rotations in SOPs with a VOPSOP of some description
perhaps. If you have the hitTime and hitN of the final collision you can
quickly blend to the normal of the collision surface over some time 'n'
using hitN-n. It's not perfect - but for tens or hundreds of thousands of
copy objects it's sufficient - and fast.

Cheers


2010/7/30 François Duchesneau <sidefx at trinix.ca>

> The following is from my Wiki. It should help. In your case, if you
> don't want rotation, make sure you don't have "up" nor "orient" nor "rot"
>
> Orienting a particle is useful when copying or instancing an object to
> it. To align an object properly, at least two vectors are needed or an
> attribute of type vector4. Houdini recognizes different attributes to
> align with the *Copy Sop* and instancing. Both *N* and *v* works in pair
> with *up*. *rot* and *orient* are vector4 quaternion attributes. Each
> one supersede others in the following order (The ones below override the
> ones above).
>
>   1. v and up
>   2. N and up
>         1. rot is added to ones above
>   3. orient
>
> François
>
> jacob fisher wrote:
> > Hey there,
> > I'm running a simple sim bouncing particles on a surface.
> > However, when I copy geometry there are odd rotations in the
> > particle/geo and when they come to the final resting spot, they
> > usually land at various angles.
> >
> > This is just a simple POPnet (location, force, collision, split,
> > interact, force, collision) set up that goes out to a copy.
> >
> > Is there any particle tool I'm not familiar with to kill rotation? or
> > to cause the particles to Y up at the end or something?
> >
> > Thanks for any help you guys can give.
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> >
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Andrew D Lyons | Digital Artist | http://www.tstex.com
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