Particle Collision Problem

[Timur Khodjaev]

I have problems with setting up particle collision.

I made simple grid geometry as collide surfase and made all conections but some particles penetrate through surface.

I have experience simulating such things in maya so first of all i tryed to find out if my particles moving too fast and rising oversampling. This lead not to solve problem but to another question. Why after i rised oversampling my particles act diffrently?

I mean after colliding thouse (who collide) seems to fly away on speed multiplyed by oversampling....

Im new with Houdini so pls point me what im doing wrong.

collision.hip

[Lukich]

Hey, Timur. I don't have Houdini in front of me right now so I can't look at your file, nut I've had this problem in the past. I couldn't replicate it in H9, but in H8 the particles whose motion vector was perfectly perpendicular to the grid would fly through. To fix it, I had to change their variance, even a small value, such as .001 would do the trick. Hope that helps.

Edited October 9, 2007 by Lukich

[SpencerL]

Why after i rised oversampling my particles act diffrently?

Oversampling forces each node in your popnet to cook more than once per frame depending on what your oversampling is set to. So if your oversampling is set to 2 then your sim would calculate each node 2 per frame. If you are birthing 100 particles per frame, setting your oversampling to 2, that would mean the node cooks twice and therefore you would really be birthing 200 particles per frame. Thats probably the main reason your sim is diiferent when you change the oversample.

[dbukovec]

hi!

I have a similar probelem with collisions, but not with the first collided ones, rather with the second which I emit from the first collided particles.

I set the second particles to slide and half of them is falling trough the surface. I have set some collision tolerance on the collision node and a bit of variance in the split node.

Any advice please?

thanks

ah found another topic, had to offset the original surface a bit, so everything is fine now, sorry

Edited October 11, 2007 by dbukovec

[EffectsPanda_at_large]

Hey, Timur. I don't have Houdini in front of me right now so I can't look at your file, nut I've had this problem in the past. I couldn't replicate it in H9, but in H8 the particles whose motion vector was perfectly perpendicular to the grid would fly through. To fix it, I had to change their variance, even a small value, such as .001 would do the trick. Hope that helps.

You could try to increase the step size, I cant remember the node's name. By increasing the step size you would be adding in between steps. Also on the collision node you could adjust the tolerance i believe I usaully set this to .0001. If that doesnt work then you could use a limit plane and just kill the pesky variants. Or you could setup a group that tracks the xyz and when that value is met or exceeded then just kill that group.

The effects panda