[Sidefx-houdini-list] Pop : Limit the number of particles

Olivier Jeannel facialdeluxe at gmail.com
Fri Mar 18 17:53:47 EDT 2016


Hey Michael, thank you !
I'll try your solution on monday (weird this is a Detail, I would have say
"Point" in the first thought)
I was thinking maybe also trying to work with particle states, but I'm not
sure this (ice) feature exists in Houdini.

On Fri, Mar 18, 2016 at 10:40 PM, Michael Dunkley <mdunkley at gmail.com>
wrote:

> Hey Olivier, the pop source node automatically attaches a detail
> attribute, called "nextid", to pop geometry that describes which
> particle id is next in line to be used.  It's technically possible to
> reference this through expressions in your activation parameters.  So,
> impulse activation could be (for instance):
>
> detail("$DOPNET:popobject1/Geometry","nextid",0)<100
>
> Note that you may have to change "popobject1" depending on what your
> particle object is called.  popobject1 is the default name from the
> shelf operations.
> I suspect this is not a hundred percent solution, as that number would
> only be updated between cooks.  If you're emitting very slowly, then
> probably everything would be fine.  But if you're emitting 10000
> particles on frame one, it would birth all 10000 particles, then stop
> on the next frame (or substep) as "nextid" would then be 10001.  Might
> work well for efficiency's sake in concert with Steven's delete
> solution, so that you'd be both stopping emission and running cleanup.
>
> mike
>
> On Fri, Mar 18, 2016 at 5:10 PM, steven ong <steve_nong at pointy.tv> wrote:
> > Hi Olivier,
> >
> > The POP Kill is deleting the particles.
> >
> > If you're trying to emit particles one after another, you have to either
> > delete the points one by one in SOPs and set Emission Type to All Points.
> >
> > However, in the old POPnet, you can put down a grid as a source and in
> the
> > Source POP with Emission Type as "Points(ordered)", set Constant
> Emission to
> > $FPS so now you'll get a particle per frame in the sequence of the point
> > number order of the grid.
> >
> > This functionality is missing from the new Source POP in DOPs. :(
> >
> > Cheers!
> > steven
> >
> >
> >
> >
> > On 03/18/2016 13:55, Olivier Jeannel wrote:
> >>
> >> Thank you François,
> >>
> >> But then, in Pop, how do you do you have the particles to move one after
> >> the other and not all at once ?
> >> Thank you Steven,
> >> It works very well ! But should I consider that it delete particles, or
> is
> >> the emission simply stopped ?
> >>
> >> Thank's for your help :)
> >>
> >> On Fri, Mar 18, 2016 at 9:47 PM, steven ong <steve_nong at pointy.tv>
> wrote:
> >>
> >>> Hi Olivier,
> >>>
> >>> You can do this very easily with the old POPnet as there is a "Max # of
> >>> Particles" parameters. If you don't need the new POPnet functionality,
> >>> you
> >>> can consider use the old version.
> >>>
> >>> Else, in a Pop Kill, you can use the following expression under the
> Rule
> >>> tab:
> >>>
> >>> if(@id>999)
> >>>     dead=1;
> >>>
> >>> That should limit the number of particles to 1000. Hope this helps.
> >>>
> >>> Cheers!
> >>> steven
> >>>
> >>>
> >>>
> >>> On 03/18/2016 13:39, Olivier Jeannel wrote:
> >>>
> >>>> Hi there,
> >>>> A very simple noob question :
> >>>> In  a Popnet, using a PopSource node, I'm using Impulse Activation and
> >>>> Impulse Count.
> >>>> I would like the emission to stop when a certain ptnum is reached.
> >>>> I tried in Impulse Activation the following expression :
> >>>> if (@id >100, 0, 1)
> >>>> But no luck.
> >>>> I'm sure I've seen it somewhere inside one of the 300 tutorials I've
> >>>> watched but I'm too dumb to find it :/
> >>>>
> >>>> Can someone give me the correct expression ?
> >>>>
> >>>> Thank you :)
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