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Add roation /spin to POP Grain particles based on clump possible?


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Hello folks,

Newbie here. I am trying to make some foam particles with POP Grains. So far the motion is coming along well what I am missing is the particle spin based on clumps it has formed. In Maya Nparticles the particles rotation is computed dynamically. I wonder if there is a way to do the same with POP Grains & link the rotation or spinning speed based on the clumps. Any Idea or workaround would be great !



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Hey Vikas, 

I recognize you from the Maya beta and on the cgtalk. Making a switch huh? ; ) Anyway did you try using the pop spin? you could use that and multiply that by attractionweight attrb. Remember that you can use any of the pop forces with grains as well.

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Hi Hernan , you got me.. yes its been Six months I did the switch. From SOUP to Houdini..life is much easier & nice. Still learning & exploring. I haven't used the Pop Spin yet ..will give a try. Thanks :) 

P.s : Not looking for Per-particle spin instead I would like to spin the clumps !

Edited by viki164
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Apologize I don't have anything handy at the moment. The test I did is at work :(.

The setup is quite simple though. I don't have any complicated graph Just few nodes because Pop Grains alone itself does the trick. I made a small geometry patch on the ground plane. Then used pointsFromVolume & Added another AttrWrangle node for randomizing pscale & mass.

f@pscale = chramp("pscale", rand(i@ptnum)) * 0.015;

f@mass = f@pscale / 0.55;

These points were fed to Pop Network as First Source Input. Now inside the Pop you put a Pop Grain Node. The settings for PopGrain to imitate Foam behaviour are : 

Particle Separation : 0.05

Constraint Iterations : 60


Friction :

With Colliders : 0.2

With Particles : 0.1

Accurate Friction Checked

Static Threshold : 0.5

Scale Kinetic : 4.5

Internal Collision :

Weight : 1

Stiffness : 1

Enable Mass Shocking Scale = Local

Shock Scaling Power = 100 & Shock Axis : 0 1 0

Clumping :

Weight : 2

Stiffness : 0.5

Explicit Constraints :

Weight : 0

Stiffness : 100

Target Pins :

Weight : 1

Stiffness : 0.5


Max Neighbors : 35

Neighbor Query Scale : 2.75

Max Accelaration : 5

Velcoity belnd : 5

Over Rlaxation : 2 & Open CL is checked ON

Just by these settings it should give you the foam behaviour & clumpiness. Add the ground as static collider.

I also Added a bit of Gravity : -9.80665 * 0.3 & Pop Wind :

// Pass Through
wind = wind;

airresist = smooth(0, 1, fit(v@P.y, .02, .22, 0, 1));

Amplitude : 0.25 , Swirl Size : 0.5 , Pulse Length : 20..

Just by these few nodes..you might get the foam behaviour. Reference :






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