Quick question - how can I tell how long a particle has been in a group? I would like to do a group switch after a particle has been in a group for a specified period of time.

You can create an attribute on the group.

source->group->attribute pop (set the default value to -1, set the group name to be the groupname created by the group pop)

in the attribute pop input: if($myattrib==-1, $F, $MYATTRIB)

This will record the frame in which the point joined the group, at which point you are free to compare it $F (current frame) or whatever else grabs your fancy.

G

ps: When working with particles, the spreadsheet is indispensable.

Fantastic. Thank you!

And, yes. I use the spreadsheet a lot. I think it is a great feature!