Group Attribute

[galagast]

Looking at the Geometry Spreadsheet. A Group SOP creates an attribute like "group:foo":

I can easily access that group "attribute" in a Wrangle like so:
 

i@myvalue = @group_foo;

QUESTION:
How do I access that group attribute on parameters that requires an attribute name?

 

For example, in a Color SOP's Random from Attribute:

Or on a Delete SOP's Filter Expression:

Although I know that I could just type the group name on the group field. I'm just curious if there's a way to access the Groups data as "Attributes".

Particularly, I'm asking because I want to access Groups as an "Attribute" in the Enable Solver DOP without actually creating an actual attribute to represent the group:

Hopefully I'm just missing or forgetting the proper syntax..

 

P.S. The Enable Solver could use an option where it can check for existing groups. I'll probably send an RFE

 

Edited January 16, 2017 by galagast
spelling/grammar fix

[haggi]

Since you create a group, all follwing nodes could simply use the group "foo" in the group attribute of any node. But this does not explain why the @group_foo does not work.

[Skybar]

I don't think you can access groups as an attribute outside of vex. The docs call it a "special virtual attribute": http://www.sidefx.com/docs/houdini/vex/snippets#accessing-group-membership

"Special" meaning it's probably exclusive to vex, at least thats my interpretation. 

[LaidlawFX]

Groups used to be a different collection of data with the geometry, so how you read/write to them was technically very different. Relatively recently in h12/h13/h14 as they updated the geometry library they began to handle groups the same ways as attributes data on disk. However groups still maintain there own series of rules and parameter options as described. If you want a group to act like an attribute just convert it, it will be better in the long run. You'll have to request a bunch of RFE to get full parody. I actually stopped using groups all together, it makes it easier.

[galagast]

Thank you for the insightful input guys. I do remember not seeing those group attributes on earlier versions of Houdini.

For what I'm working on now, I did end up just converting it to an attribute instead