[Sidefx-houdini-list] Split POP confusion

Peter Robbinson probbins at sympatico.ca
Wed Oct 22 15:52:38 EDT 2008

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.


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)
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