[Sidefx-houdini-list] Split POP confusion

Jim Price shadeops at gmail.com
Wed Oct 22 16:18:42 EDT 2008


Ah yes.  You're both right, particles created from a Split POP don't return
to the same stream.  However, Groups in POPs are global and this creates a
loophole that you can exploit.  By adding the split particles to a base
group you can trick POPs into being 'recursive'.

Here is a thread on the SESI forums dealing with this.

http://www.sidefx.com/index.php?option=com_forum&Itemid=172&page=viewtopic&t=6162



On Wed, Oct 22, 2008 at 3:52 PM, Peter Robbinson <probbins at sympatico.ca>wrote:

> Okay, I seem to be missing something then. It works for me.
>
> I generate particles from a grid, colour them, use a fan to blow some of
> them; then split them.
> The split particles are reacting to the fan, just as the original
> particles are.
> Provided I create a birth group name for the split particles, I can
> split those with another split pop and those in turn will react to the
> original fan.
>
> PeterR
>
> Andy Nicholas wrote:
> > Thanks for the replys. Larry, I think you've hit the nail on the head. It
> > would seem that the way things are set up, a split node can never split
> > particles that it generated (since by definition they can never be fed
> > into the Split's input connection).
> >
> > Wow, that totally sucks. It basically means that you can't do any sort of
> > recursive spawning of particles without putting down a separate Split
> node
> > and copying the tree for every level of recursion. Surely this should be
> > bread and butter for a decent particle system? I'm amazed that Houdini
> > can't do it!
> >
> > As a workaround, I think the only way I can do this will be to do it all
> > in SOPs and use a SOP solver. Not ideal, but as far as I can see it
> should
> > work.
> >
> > Cheers
> >
> > A
> >
> >
> >
> >
> >
> >> On Wed, Oct 22, 2008 at 10:31 AM, Andy Nicholas <andy at andynicholas.com>
> >> wrote:
> >>
> >>> Thanks for the responses. You're right, if it was just a case of
> getting
> >>> it all to be affected by those nodes, I could probably rejig the order
> >>> and
> >>> it'd work. One thing I neglected to mention though is that I need the
> >>> newly split particles to also be able to split themselves under the
> >>> appropriate conditions.
> >>>
> >>> The only work around it would seem, is that I'd have to copy and paste
> >>> the
> >>> whole POP network N times after each Split POP, where N is the maximum
> >>> number of generations of bubbles. Not exactly a great workflow :-)
> >>>
> >>> I just need the particles to be treated as normal particles, and not as
> >>> if
> >>> they're totally separate, as they need to go back through the same tree
> >>> (i.e. with the split POP). The Collect POP doesn't seem to have any
> >>> affect
> >>> on any of this.
> >>>
> >>> So is there really no way I can just tell these new split particles
> that
> >>> they're exactly the same as the other particles? Do any of the lineage
> >>> type of attributes have any effect on this? How is Houdini keeping
> track
> >>> of which particles are which?
> >>>
> >> Place the gravity & collision nodes after the collect pop.
> >>
> >> source ----> split
> >>     |               |
> >>     |               |
> >> collect <-------+
> >>     |
> >> gravity
> >>     |
> >> collision
> >>
> >> (hope this formatting works)
> >> _______________________________________________
> >> Sidefx-houdini-list mailing list
> >> Sidefx-houdini-list at sidefx.com
> >> https://lists.sidefx.com:443/mailman/listinfo/sidefx-houdini-list
> >>
> >>
> >
> >
> > _______________________________________________
> > Sidefx-houdini-list mailing list
> > Sidefx-houdini-list at sidefx.com
> > https://lists.sidefx.com:443/mailman/listinfo/sidefx-houdini-list
> >
> >
>
> --
> "gravity is not a force, it is a boundary layer"
> "everything is coincident"
> "Love: the state of suspended anticipation"
> "To get any appreciable distance from the Earth in
> a sensible amount of time, you must lie."
> "Easy, is not how you make a living."
>
> _______________________________________________
> Sidefx-houdini-list mailing list
> Sidefx-houdini-list at sidefx.com
> https://lists.sidefx.com:443/mailman/listinfo/sidefx-houdini-list
>



More information about the Sidefx-houdini-list mailing list