Why is it not possible to delete single GroupIDs?

[Xaymar]

I currently have a problem with PhysicsMaterials.
I haven't figured out why it's not possible to delete a single GroupID, but possible to delete all of them. Where's the problem with deleting a single GroupID?

I'd like to see this added, or at least explained why it isn't possible. Thanks in advance.

[Julio Jerez]

If it a weakness of the engine. I never bottere to add that funtionality.
Basically the hash table that is used for Material System does not allow for removal on single entry without rehashing.
plus it is not that simple to change after all that is build on top of the system.

I could add that funtionality, however like the Predefined internal joints which are replaced by open source joint library,
I do not want to expand the inernal Material System because I want to encourage people to use the ShapeIDs and build thier own application side material system,
Here is an example of a Flexible Material System that uses the Shape ID, and it is all open source.
http://newtondynamics.com/wiki/index.php5?title=Tutorial_201:_-_Advanced_Custom_Material_System

This is very symilar to the one that is used in the engine. But it uses the shapID instead of the BodyID.
It is way more powefull since it allow for unification of Collison Tree, and convex, and Terrain in a singel callback system.

you can even mix both system