[Sidefx-houdini-list] Killing cached sim particles

Andy Nicholas andy at andynicholas.com
Fri Oct 24 09:21:32 EDT 2008


Thanks a lot Nick. Yep, I figured that I could probably use CHOPs somehow.
Thanks for digging that solution up.

(I'm disappointed by DOPs though, I'd have thought that this sort of thing
should be bread and butter for it. )



> Ok this would work.
> Just use the count chop to set the custom delete attribute to clamp from
> its highest value for the rest of its life :¬) Might be worth setting up a
> nice little digital asset for this, as its useful for more then just
> particles but other time/volume based geometry deletion.
>
> Might get alittle sluggish and heavy in memory usage as it is Chops after
> all.
> Nick
>
>
>
>> From: nick_p102 at hotmail.com> To: sidefx-houdini-list at sidefx.com> Date:
>> Fri, 24 Oct 2008 12:58:39 +0000> Subject: Re: [Sidefx-houdini-list]
>> Killing cached sim particles> > Ah yeah that is a problem with the sop
>> solver too, as all of this will be based on changing point orders. Darn
>> it.> > I wonder if you can pass a custom attribute to the particles from
>> the volume, and in sops pass the data to chops using $ID as your
>> attribute to organise the chops with. Then somehow find the first peak
>> in that chops attribute and set it to that for the rest of its life,
>> dont forget to assign it back to the points using $ID again. Which would
>> then allow you to delete the points. Im not sure how you find the max
>> value and clamp it to that afterwards though. Just an idea.> > Hope you
>> figure this out :¬)> Nick> > > > > Date: Fri, 24 Oct 2008 14:39:42
>> +0200> From: ben.schrijvers at guerrilla-games.com> To:
>> sidefx-houdini-list at sidefx.com> Subject: Re: [Sidefx-houdini-list]
>> Killing cached sim particles> > Hi Andy,> > That's a tricky thing. The
>> easiest is to do it at simulation time as you > might expect.> > In a
>> cached situation you're best of in SOP's.> The tricky bit is that the
>> Delete or Blast Sop only know about point > numbers but the point
>> numbers of your particle system are probably changing.> What's not
>> changing is the particle ID attribute. So you could use an > expression
>> in the Delete Sop to delete the points in question.> Something like:>
>> $ID==19338 || $ID==2403 || $ID==1653 || $ID==8328 || $ID==3278> > If
>> it's a lot of particles that need to be deleted you might have to run >
>> through the whole sequence and find all to be deleted points.> Somehow
>> you have to get those ID's into a text file. Then make some > scripts
>> that removes the doubles occurances and builds you the string > you need
>> for the Delete Sop.> I've actually see people doing that in the past.> >
>> succes,> benS> > Andy Nicholas wrote:> > Hi,> > Forgive the torrent of
>> questions from me at the moment. I've got a tough> > simulation job on
>> at the moment and it's turning out to be a great> > learning experience
>> :-)> >> > Anyway, my question... I've cached some particles into some
>> .sim files and> > I've then loaded them back in to an empty DOP network
>> using a File DOP.> > What I'd like to do is to delete particles that
>> venture outside a> > specified volume, but delete them permanently so
>> that when their original> > trajectory comes back into the volume they
>> don't reappear.> >> > I've tried feeding the File DOP into a popsolver
>> and then putting it> > through a Kill POP in there, but no joy. I'm
>> guessing there's a trick to> > this, but I don't know where to start
>> looking.> >> > Any pointers on this would be gratefully received.> >> >
>> Thanks> >> > Andy> >> > _______________________________________________>
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