Can anyone help me answer my curiosity? So, it's about rigging. how could this happen ?

[hello_rioalexander]

when I press shift p on the keyboard to unparent a joint in the Maya outliner, a transform group appears, why does that happen and how to solve it?

[aldentesinferno]

Well, my first thought is that Maya's doing that to maintain the position of the joint somehow?  If you've frozen the transform of the control above the joint there might be some funky hidden math going on to maintain the pivots or something.  Are the created groups all zeroed out or do they have any rotation/translation/scale/etc.?

[Kahylan]

Hi!

This happens when a parent of your joint has a scale on it that isn't (1,1,1). Because of the scale compensate function and the joint orientation of the joints. Maya needs to do this to keep them in the same position when you unparent them.

My guess would be that you didn't mirror the joints properly (using the mirror joints tool), but instead just used a group set to sx = -1 to mirror over.

To avoid this,  use the mirror joints tool with a parent joint on the mirror axis using the mirror joints tool and then reconnect the joints to the rest of your setup. You probably could also reset your transforms and include "joint orientation" in the resets, but I'm not sure how well that works out, and if you are doing any matrix based rigging, I would strongly recommend against it.

I hope it helps!

[hello_rioalexander]

 I've tried it but it's still the same even after freezing rotation, scale and translation

[jljinBQKEA]

I found if you freeze transformations for the parented transform shape/group, you can then unparent the joints and delete the transform shape