Hi,

I've got some questions on workflows how to copy/ instance POP Nets.
I am visualizing parts of a machine.

There are 70 rows and each row has 25 valves. There are particles supposed to be coming out of each valve.

The geometry (incl. valves) was imported from another 3D package, I am just dealing with the particles.

Now, I created a POP network for one valve. The particles are pretty much doing what I want them to do and so I duplicated the POP network 25 times so now particles are coming out of each valve.

The problem is, the particles are looking quite boring because they are all doing the same. Also, I they need to be having a different moment for emission- which they do not have.

How do I copy/ instanciate particles best in Houdini?

lots of ways to do this, but the easiest might be to write out your particle simulation to disk as geometry, then use a delayed load shader to load in your particles to your instances. in the file parameter of the delayed load shader you can use an expression like
…../particlespray.`rand(instancepoint())*10+$F`.bgeo
to offset the $F value. to read in different values.

Ok, the delayed load shader seems to be pretty interesting.

I've still got a different question. I copied my POP Network using a copy SOP. In the copy SOP, I activated two of the stamp values and connected those to my original POP Network using expressions (Start Time and Random Seed).

Although both fields in the POP Network are colored cyan, now I think this hasn't got any effect as all the copies are looking the same.

Another problem is some of the particle sequences are colliding with (the very same) geometry object, others don't. But all the copies act as if they don't because the original POP Network doesn't.

So I am wondering if my idea of creating several POP networks via the Copy SOP might be working at all?

Hi hi,

i often question why stamp isn't working, appears that “Stamp Input” checkbox wasn't ticked.

eitht.

Well, it is ticked.

you cannot use copy stamping with live simulation like POPs
it doesn't work that way because in each frame/timestep you are constantly changing the parameters of POPs by stamping and then when you advance to next frame/timestep POP network will lose track of it's history

you need to cache particles first or make more versions which you then copy

or you can simply copy emitter points with changing attributes or whatever and then use single POP network after the copy to simulate particles coming from all valves and because attributes (like v N or other) for each valve emitter can be stamped you will get different emission from each valve

Thank you very much, this makes it clear for me.

You can move your POP simulation in to DOPs and then you get caching and stamping will work.

I attached an example that shows point cloud lookups working with POPs wrapped up in a DOP network.