Biped's Weird Hierarchy

[FluffyVox]

Hi,

I noticed today that the parent bone for biped's thighs/legs is the first spine link. I would have expected it to be the pelvis or bip001. It's also weird that the clavicle bones' parent is the neck rather than the last spine link.

We are exporting biped to a game engine so the weird hierarchy is problematic for our in-game IK solution etc. Given that, I tried reparenting biped's bones (thighs to pelvis etc) and it all seems to work okay in Max but I'm a bit worried about changing the hierarchy in case is causes and issues/problems further down the line.

Is there a technical reason why biped is set-up in this way and does anyone foresee any issues with changing it in Max?

Thank you!

[dmitriy.shpilevoy]

Full body IK and reparented bones sounds like a dangerous combo. If you share animations between a character like that and the one that has reparented bones then I would expect some problems. Just a hunch, didn't try it.

If reparented character uses its own animation then it should be fine. Game engine probably doesn't have specific expectations for bone hierarchy, since it doesn't know if you using a human with bip skeleton or a chicken with custom rig.

[FluffyVox]

Hi, thanks for replying! I also thought it sounded like a dangerous combo but from what I can tell, biped still loads animations in without a problem (even with the different hierarchy), and the IK still seems to work okay which is why I was wondering if Autodesk could shed some further light on this and whether or not it will cause any issues.

As for the our game engine - it does of course support any kind of bone set-up, but our joint constraints and IK set-up (when entering ragdoll etc) requires the hierarchy to be set-up in a more conventional way. Upper thighs linked to lower spine (like biped) is just bizarre when compared to most rigs. Just looking for any insight as to why and then perhaps we can work out how to best handle it.

[FluffyVox · Accepted solution]

Just to follow up on this in case anyone else is confused by biped's default structure! Turns out, I just needed to pay closer attention to the set-up options in Figure Mode. Or read the manual - my bad. By default, "Triangle Pelvis" is on, and links thighs to the lowest spine bone so you just have to switch that off.

The other default setting is for "Triangle Neck", which is off by default. Switch it on to link clavicles/shoulders to the top spine bone rather than the neck.

So to summarise, to achieve what I was looking for, you have to set the inverse of biped's default settings for "Triangle Pelvis" and "Triangle Neck".