What Are The Limitations Of Imported Skeletons?

Hey everyone, hope all is well!

I’ve come to a point in development where I would like to create a better rig for the characters I’ll be creating. As I’m coming from a Unity background, I’ll be using terms that are native to that environment to hopefully better illustrate what I’m asking.

Within Unity, in order to fully utilize all of Mecanim features (IK and retargeting being the ones that come to mind,) you had what I would call a rigid hierarchy of bones and a pretty set number of bones. Anything deviating from their standard would disqualify your character for retargeting, for instance, and if I remember correctly, even IK wasn’t an option at that point.
Such things that I’ve grown accustomed to, such as twist bones, simply weren’t something you could feasibly do if you wanted any advanced features of Mecanim. More than two or three spine bones? Good luck getting that to work.

I mention all of this to say what the title implies: within UE4, what sort of skeletons am I limited to if I want features such as retargeting and IK? So far, I’ve not seen anything definite concerning this topic. I know that to share animations and have the ability to retarget, your characters need to share a common base skeleton, but within that base skeleton, can it not have twist bones, for instance? How many bones are you limited to within any given part of the character?

I suppose what it all boils down to is this: are you locked into very specific standards when it comes to what kind of skeletons UE4 accepts, and in general, what are the specifics as to what you can and can’t import?

Thanks, and take care!

Hey, that sounds horrible limitations in unity. Tho im sure itll be better nowdays.
Anyway, in in ue4 its actually quite flexible. My current characters have rather complex skeletons. around 400-500 bones including twist bones for all limbs, facial bones, and a lot of additional deformation helper joints.
Our skeleton also has different number of spine bones than ue4 skeleton and a different hierarchy setup for spine (No static hip joint) as well as several other differences in orientation, general positioning, naming and parenting of bones. But we still managed to retarget plenty of animations from ue4 mannequin using ue4 retargeting tool, worked rather well. Its not a final solution for advanced rigs as ours - we still have to do the final retargeting in maya to make sure all auxiliary bones move along since they have their setup done in maya.

Regarding twist bones, only important thing is that they arent a chian but rather individual children bones of the main limb bones. Except for that, I havent encountered any hard limits regarding skeletons alone. Theres still some annoying soft limits with the number of bones in a single skinCluster, but thats a different topic.

Hey Adeptus, thanks for the response!

Hm, very interesting stuff, so there’s no real hard limit to what you can have inside UE4? That’s really nice to hear. =-)