View Full Version : nParticles inherit collision velocity

12 December 2010, 10:29 AM
Hello all,

I have a nParticle emitter spraying particles on an animated object in Maya 2011. The animated object is a passive collider and I want particles to stick to the surface. Everything works fine except for the fact that nParticles inhert the velocity of the face they are colliding with. That's not what I want. I've tried a combination of settings on both nParticle and nRigid nodes with no luck. The logical values for this would be 0.0 Bounce, 1.0 Friction and 1.0 Stickiness but velocity is still inherited. I've been looking for other collision settings on the solver/particles/rigid nodes but nothing else seems related to this.

Any help would much appreciated.

12 December 2010, 07:17 PM
have you tried reducing the mass and speed of your particles?

To give an analogy... its harder to stick bowling balls by flinging them at a wall than gently tossed ping pong balls. you would have to have extremely high friction and stickiness on the wall to hold onto a fast moving bowling ball.

Generally speaking, once a particle collides with a surface i want them to stick to, I would even want to move the particles into a separate particle shape, that has very little external forces, friction, no conservation, things that interfere with the underlying object motion and the ability of the particle to stick to it.

look into collision events and per particle expressions for your solution if you cant get it working with mass/speed/stickiness options alone. There are ways to avoid making separate particle shapes, etc if you dig into some of those particle attributes.

also take a look at soup nodes by mr shipkov, there are even color terxture transfer nodes based on particle impacts, so if you are just looking to "paint" your object, then sticking particles might be overkill. processing, caching and simulation time wise.

12 December 2010, 08:12 AM
( the mass and speed does tone down the effect but that's not what I want as this would affect my whole simulation and not just the collisions. The effect I'm looking for is foam so i guess this is a "special" case of physics.
I eventually I used an expression to goal the particle based on collision U&V and from those particles to give birth to more particles to have the dripping effect that works quite nice with nParticles and self-collisions. However I can't help but think that most of this could be avoided with some extra interface collision control.

SOuP looks very interesting, thanks for your reply and tips.

12 December 2010, 03:02 AM
i suggest looking into per particle expressions that only affect mass on impact, or temporarily multiply the velocity by a fraction or 0 upon collision. that will give your particles more time to stick onto the surface. yes, emitting additional particles also helps, especially if they are emitted with less mass than the initial collider.

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