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catchyid

FLIP Particles Exploding?

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Hi,

I have a Lava FLIP simulation, it works fine IF I don't have any collision volumes (ps. collision volumes are such spheres going upward to simulate lava bursts). However, once I enable collision volumes, the simulation works fine for a bit then particles explode (around frame 44)??? What is the best way to trouble shoot this problem? Are there some parameters that could "fix" this behavior? Note, in the pictures blow, there is only one frame difference between stable/unstable screenshots...

lava_v2.hip

stable_lava.png

unstable_lava.png

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19 hours ago, catchyid said:

Hi,

I have a Lava FLIP simulation, it works fine IF I don't have any collision volumes (ps. collision volumes are such spheres going upward to simulate lava bursts). However, once I enable collision volumes, the simulation works fine for a bit then particles explode (around frame 44)??? What is the best way to trouble shoot this problem? Are there some parameters that could "fix" this behavior? Note, in the pictures blow, there is only one frame difference between stable/unstable screenshots...

lava_v2.hip

stable_lava.png

unstable_lava.png

Cant look at the file. But if you are using a static object as collider make sure you got consistent pointnumbers. 

Edited by mawi
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Thanks... The ground is only static (it's Static Object DOP and it uses volume representation), the bubbles are "Source Volume" initialized to "Collision". Plz, see attached image. 

Actually, could you explain more what you mean by :

Quote

"make sure you got consistent pointnumbers"

because I don't understand what that means??

Thanks :)

lava_collisions.png

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I think it may be related to your wrangle which multiplies velocity in the Y direction by 5 every frame. I turned that off and simmed out to frame #68 without an explosion. I'm not sure how important that is to your final look, however?

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Its about inconsistent point counts in the bubbles collision geometry.

You are using a trail-SOP after a popnet that got shifting point count, giving "exploding" velocities on frames were a particle dies.

Put the displayflag on the vop after the trail and turn on velocity view. Play the disco :)

 

To fix this, just kill the trail2 SOP, it doesnt do anything since you apply loads of noise directy after. If you really need that velocity, just check the "use template point attributes" in the copy sop. This will let the bubbles inherit the velocity from the particles.

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Thaaaaaaaanks guys :) 

@Atom, actually the wrangler is not affecting is simulation, it's before the popnet and is just there to create initial velocity (maybe it's best to remove it altogether and initialize the velocity inside the pop, which I think is cleaner!)

@Martin, YES, you nailed the problem! I am not sure why each time I use "trail" sop, I get these problems, I've tried to use "Match by Attribute" and use "id" for the attribute but it did not work as well. However, when I think about it, there is no need for trail sop in the first place because velocity is already computed by the POP network, so adding trail node is just a waist of computation. To answer your question, indeed I need to use the pop velocity, my goal is to mix between particle velocity and a random velocity such that at the beginining of the particle life I will have the particle velocity and as it ages the noise kicks in until it dominates just before the particle dies...

Alright, once more thanks Atom and thanks Martin...

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I was having a problem with unstable fluid sim, after reading this thread just want to say THANKS!
:D

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