I was using an emit attribute in SOP to drive the birthrate inside a POP Network. I now see that each particle inherts this property, which seems unnecessary.

Is there a way to remove certain attributes from particles? In my POP Source node's Inherit Attributes field, I tried
* -emit
which seems to have no effect. I also tried manually entering all common attributes while omitting my custom ones, but the nodes then fail to cook (no useful error report).

Any suggestions?

The syntax to omit an attribute would be this:

* ^emit

Here is the doc page on Pattern Matching: http://www.sidefx.com/docs/houdini14.0/expressions/_patterns [sidefx.com] (I always forget what that page is called!)

Thanks goldleaf, you're right! I missed that.

It appears that I cannot remove the emission attribute without causing an unspecified cooking error, maybe because it's linked too intimately with the POP source. I tried removing other attributes though and that works fine!

Ah, that's because if you look inside the POP Source / sopsolver1, the node to clear attributes happens at the top, deleting the emit attribute necessary to create particles. Just unlock the OTL, and place an Attr Delete at the bottom of the chain to delete emit at the very end.

That does it, thanks again!

You can use sopsolver in conjunction with multisolver without unlocking “POP Source”.