Hello,
I am trying to port our old rigs, (which were not that hold, just a couple of houdini beta versions old)
and now I see that the flip solver is not attaching assigning an ID
to the particles in the particle fluids.
How can I get that again?

thanks in advance!

Unfortunately particle id becomes increasingly meaningless when you turn on the reseeding particles and surface oversampling. And it is recommended to use those options.

If you do want particle ids, you can add them to the default particles through creating an id attribute via a VOP SOP.

Crossposting here…

http://forums.odforce.net/index.php?/topic/15451-h12-flip-ids/ [forums.odforce.net]

I'm also wondering how to get ids working so that the ids are unique. I've tried a few things, but can't seem to get unique ids out of it. Is there an easy way to get unique ids onto the particles? I understand that turning off reseeding particles is recommended…
The reason I personally like having ids is that it's such an easy way to work with the points/particles post-sim. It makes it much easier to remove unwanted particles for the duration of the simulation. There are also other instances, where you'd want id's post-sim, such as using a copy sop or instancing. Without some unique identifier for each particle, it limits what you can do post-sim without having to resimulate.

Nevermind. There was a solution posted in there, that I somehow missed.

Could you let us know what that solution *was*? I am trying to solve this issue and there are many suggested solutions on the link you give.

Houdini 12.1.30: The FLIP Solver has a new option to add a unique id attribute to each particle. Additionally, the Reseeding operation has been updated to properly create new ids when generating new particles.


Also in 12.0.706

Thanks! I'm really just starting out, so apologies for the basic question, but:

I've clicked to add the attribute id. How do I refer to it in an expression?

Perhaps a better question is, how can I see what attributes are associated with the points so I can know what else is accessible expressions?

Is it $ID?