Hi there,

I have this particle system where particles bounce around and achieve equilibrium, but I need to have different types of particles with opposite charges/properties interacting.

I have tried having two sources in the popnet but the final output refuses to interact. (please ignore the voronoi sop). I have also tried having two separate popnets but that failed as well.

Thanks in advance!

Please play file to see particle simulation.

In the POP network, you had the display flag on the Property POP near the top. Move the display flag to the last POP in the network to evaluate the other POPs and see your particles interact.

Does that fix it?

Hi Jeff,

Thanks for the reply, The POP network works fine with a single type of particle (as it is now), but what I'm trying to do now is to add another set of negatively charged particles into the mix, so that the simulation runs two groups of particles against each other.

I'm not too sure where to programme this second set of particles; in the same popnet? or elsewhere?

Ah thanks for your help Jeff, I have found out that the particles can be sorted into different groups in the popnet, although they must be listed by number, and in a linear string. It seems to be giving the correct simulation, although this listing method seems to be exhaustive.

I don't think I have had to explicitly list particle points like that since, never. Yes you use groups quite frequently in POPs to partition and organize the POP rules.

The Group POP has a random folder that allows you to create multiple groups in one go. You can have it do a random sort through the points creating as many groups as you want or use an expression. I used an expression to mock your half division of the points using a simple if() expression as an additional modifier to the random group generation. You can use whatever expression logic you wish to generate the particle groups.

See the attached example file.

If you want to use two separate Source POPs, you need to use a Collect POP to merge the two sources together and then apply your logic. This is generally done when you have two discrete geometry sources coming in to POPs. See the help card for the Collect POP for usage. See the Orbit POP example file as it contains a Collect POP to merge in two Source POPs.

As well, you can use impulse birth with the birth rate set to $NPT to generate exactly the number of points in the source geometry in to the particle system.

It is common to use a birth group to initialize the particle attributes. In this file, the Source POP is set up to put the particles in to a group called justborn. I then create the groups using the Group parameter set to justborn. This limits the Group to only work on those particles introduced in to the particle system.

All common techniques to remove the need to explicitly list points by particle.

Ahh I see! Thanks so much for your help Jeff! The grouping before putting it into the popnet was exactly what it needed! )))