The built-in Group node has the ability to identify incoming SOP points according to a bounding object, and change the group of those points.

I have a custom simulation SOP node, and I would like to delete simulation elements that are outside some bounding object, based on their position.

I've searched the forums, however:
* I don't really understand how Solver nodes work, but I am not using one or subclassing SOP_Solver. (When I was starting off, I found no documentation on its existence.)
* The simulation is being brought in from a library (also written by my team), so the points I need to filter out are literally just a 3d vector (glm::vec3).

Thanks.

P.S. semi-related side question: the built-in nodes have (middle-click) readable labels - how can I do this?

Houdini 14.0.258 gcc4.8 64-bit