Can anyone point me to a good technique for spawning new particles at the death of other particles? Imagine a bubble popping and leaving smaller bubbles and mist

Click on the Fireworks icon in an empty scene. Once the network is built dive into the AutoDopNetwork and Double Click on the fireworks HDA. It will be greyed out when you are inside unless you enable editing of contents. But you can still see how it works. Basically it creates a group of dead particles and feeds that to a pop replicate. The pop replicate is what you would use in your situation to form the secondary spawn of smaller bubbles or mist by copying a small sphere onto those points.

Thanks for the tip, that worked even though I'm not entirely clear yet on how POP streams work. I basically copied what the Fireworks asset was doing as a pop subnet and tweaked a few things, here's the hip file works very well

POP Streams are just plain old point groups from SOPs. We actually call them “Group” by name on the various POP * DOP micro-solvers.

We had to find another name for “group” because DOPs have Groups already to create and specify Groups of Simulation DOP objects.

If you dive inside any of the POP * DOP micro-solvers you will see most likely a Geometry VOP DOP which is actually an equivalent Attribute VOP SOP working on the point geometry directly. In this world stream == group.

Knowing this is very important.

You can for example load up your incoming reference source geometry that you emit particles from with all kinds of point groups and point attributes and use them directly with POP * DOP micro-solvers.

You can partition your geometry via point groups in SOPs and then inherit these groups directly as streams in to the POP * DOP micro-solvers (which we now know are just point groups).

Hope this helps.

Very helpful, thanks Jeff! So Dead looks like an integer attribute 1 meaning the particle has died and it stores the last point position?

Yes there is a state integer attribute and yes dead is 1. The particle will be reaped on the next simulation substep.

Hey! small question! is there a way to emit another burst of particles from the replicator once the particles emitted from the first replicator have died? I am new to houdini so I am trying to get this effect… thanks!