The RBD Pack SOP packs geometry and constraint inputs into a single geometry.
The output geometry will have three packed primitives, one for each of the inputs.
rbd_type string attribute is created to allow the geometry and constraints to be split up appropriately when unpacked.
Packing RBD simulations into a single object makes it a lot easier to work with them, either using switches or merges they can be treated as a single wire. The RBD Unpack SOP will undo this operation.
rbd_name attribute to the packed primitives.
Useful when merging multiple simulations together to track them when they unpack.