You don’t like doing forum searches, do ya, M? 
I think that’s where we talked about it… and where I contributed what little I know.
Umm… do these things need a for-Ammo-only custom Babylon physicsImpostor class? Or, maybe you are planning to reach-into native land to set/get these groups/masks? shrug (thx for your work on this stuff, guys. Advanced Ammo things.)
Background Info: Collision filters/masks COULD be important on the knee or elbow joints of a physics-active ragdoll. At these joints, the “shape” mesh attached to the physicsImpostors (on each end of the physics joint)… is sometimes a mesh with some “diameter” (fatness). And sometimes there is very little space/gap between the mesh shapes… AT the joint.
SO… when the joint bends WITH COLLISION ACTIVE… the shapes collide with each other… after the joint bends VERY LITTLE angle-amounts… and this gives you a stiff/inflexible ragdoll… like these. But MAYBE… these ragdolls are stiff because of using single spring-joints (as opposed to hinge-joints), and not stiff due-to shape collisions.
All in all, not much bend amount allowed on any joint, there. All of the joints on those ragdolls… have angle limits that are (possibly) dictated/controlled by shape collisions of the mesh on each end of the joint.
A BETTER ragdoll would not use shape collisions, and would allow the shapes to overlap. Then, the ragdoll would use joint angle limits/settings… which could be set to simulate ACTUAL HUMAN joint-bend-angle limits. More flexible, more realistic “raggies”. Or “raggars”, as @Raggar might call them.
We want the shapes on each side of a joint… to STILL be collision-active, so they can impact with the cannonballs we fire at our raggies. BUT, we don’t want certain “specific” body parts to collide with each other. Precision collision… done with groups and filters. It’s similar to the includedMesh and excludedMesh… for our BJS lights.
I THINK… this is a decent example of when/where… collisionFilterGroups, collisionFilterMasks, and collisionObjectWrappers… might be used. Not sure, though, as I have ONLY done some of this stuff… in Oimo. Perhaps this flavor of talk… should happen in that other thread.