Limiting POP Force effects

[Ledenko]

Hi Guys! I'm learning Houdini and I'm trying to get particles to cast from an object and then take the shape of another as defined by the goal. Basically, the particles are attracted to the goal points and when they get close enough, they get thrown into a new group which ignores the attraction and moves as defined by the goal (or I could do it based on life, an idea for myself). To add noise to the setup, I created a POP Force node and limited it to the group of newly created particles, as defined by a POP Group (if it's a particle, it belongs to it until it doesn't, simple enough), but the problem I'm getting is the noise is also affecting either the goal geometry somehow or the particles that are sticking to goal and it wobbles around a bit. I'm probably missing something fundamental, but I'm at a loss as to what. Please help

[argilop]

Hi, 

 

Check if the particles are leaving the previous group (the one that is affected by the noise). If not, you can create an if statement with a POP Wrangle to remove the particles from that group. 

[Ledenko]

I don't think they are, unless they can somehow be in two groups - I set up colors so I can visualize group changes. Also, the POP Force effect is much greater on the particles that it's supposed to influence than the goal points, which only wobble slightly compared to the force noise. And unfortunately it seems I forgot to save it
 

edit: never mind, I did save it, I've attached it if anyone can review it and tell me what I've done wrong.

particlegoals.hip

Edited September 15, 2015 by Ledenko

[argilop]

Well, I had a look to your file and I added a wrangle to remove the particles from the first group. Basically you were grouping all the particles inside the newborn group (if you middle click on the node you can see how many particles are in each group) I also add a @dist which is more accurate than the @nearestdist.

 

Hope that this is useful for you!

 

Arnau

particlegoals_fixed.hipnc

[argilop]

And the problem you are having with the forces is because your POP Attract is affecting the newborn group. If you change that to attract the nearby group, you'll get closer to the effect you want

[Ledenko]

So that's it, particles belong to as many groups as you'd like, this was the key info I was missing. The thought has crossed my mind, but then I wasn't sure how to set up group related vexpressions. Thanks!