[Sidefx-houdini-list] accumulating particles

Craig Zerouni craig at zerouni.com
Mon Mar 3 00:53:55 EST 2008


Actually, this also works in H8.X. I had a nifty little demo I used to 
do of just this trick.

(wait, did I just correct Jeff Wagner? Must lie down...)

CZ

Jeff Wagner wrote:
> There is doubtless a more current method to affect
> a similar effect.
>
> Yep. H9(.1) has a few ways to do feedback. Building your POPs inside a 
> DOP sim then using a SOP solver to read the particle cache and do your 
> work there should offer you the missing functionality. You could 
> generate your point cloud in the SOP solver per iteration...
>
> There is also the "time*" SOPs (time blend, time shift, time warp) along 
> with the foreach SOP to do time based shifting and feedback.
>
>
> -jeff
>
> caleb at howlor.com wrote:
>   
>> In the absence of a Feedback SOp, I sometimes write particles out to a
>> file, and then read them back on the next frame by means of a VEx POp, or
>> another type of custom operator.  The only real awkwardness of this method
>> is that it necessitates executing one's playback from an output node - to
>> get the sequence to write.
>>
>> By reading in the previous frame's particles, and using point cloud
>> functions to suss the previous state, and modify the behaviour of the
>> particles on the current frame according to what came before, I've been
>> able to affect some pretty interesting behaviour.  Stacking snow by this
>> sort of mechanism should be pretty easy.
>>
>> Of course, I started doing this right after the Feedback SOp was taken out
>> of PRISMS - in protest.  There is doubtless a more current method to affect
>> a similar effect.
>>
>> This is how I did the perception systems for the flying snakes in
>> "Elektra", crowds in "The Sum of all Fears", and 16,000 mice in "Cats and
>> Dogs".
>>
>> Point clouds make it *fast* to handle huge numbers of particles, and allow
>> for more stable, and abrupt interaction than the falloff model employed by
>> the interact POp.
>>
>> I love me some particles!
>>
>>
>> -caleb
>>
>> Original Message:
>> -----------------
>> From: Jed Schwartz jed at jedschwartz.com
>> Date: Tue, 19 Feb 2008 10:03:29 -0500
>> To: sidefx-houdini-list at sidefx.com
>> Subject: [Sidefx-houdini-list] accumulating particles
>>
>>
>> I'm suffering from a Particle brain freeze-- I need to accumulate  
>> particles on top of particles- (like accumulating snow) Stick on  
>> contact puts particles in place on the ground plane-- how do I get  
>> the following particles to stick to the existing "stuck" particles-?
>>
>> Thanks!
>>
>> Jed-
>>
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