Joints not positioned properly when exported to FBX

[RyanJP]

I've merged 2 skeletons together but I must have missed something because when I import to C4D the hands are in the complete wrong place in world space. Thought if I edited the path attribute it would fix the hierarchy, but it did not. Works fine in Houdini. What am I missing?

 

RigTemp.zip

Edited September 29, 2022 by RyanJP
wrong file

[madebygeoff]

It's gonna take me a little more time to figure out exactly what's going on, but a quick look and it looks like there's might be a mismatch of scales. It looks as if the hands are coming in from the output FBX at a different scale than the rest of the skeleton.

There's a couple issues with your skeletons:

First, the joint orientations aren't consistent within each skeleton. They are consistent (or at least consistently inconsistent) between skeletons, so that's not what's causing the problem with the hand positions. But it can cause other problems later. On both skeletons the arms are oriented with +X toward child. The legs are -Y. And the spine is +Y. Since FBX imports usually assume a consistent orientation, I was getting errors when I brought in the output skeleton. Append an orient joints SOP to both skeletons to get more consistent orientations.

Second, is you've got scale problems. The 3@transform attribute encodes rotation, shear, and scale. At first look, the scales of each skeleton seem to be the same, although the scale inheritance is 0 on some joints (this combines local and world transforms) and 2 on some joints (scale and offset). I quickly reset the scale inheritance hoping that would fix it, but it didn't. I think I'd have to rebuild the transforms so that they all match, which would take a bit of time to figure out.

When I have a little more time, I'll try to take another look. But maybe that's a helpful start?

Depending on what you are trying to do, instead of merging the skeletons you could also try to retarget the movement from one to another. That way you don't run into problems of frankensteining together two different skeletons.

[RyanJP]

Thanks Geoff! This actually was an issue with the Path attribute having 2 hand paths, I deleted the attribute and it all worked fine. I actually don't remember what version of the file I posted here as this was a while back, but I did eventually resolve the issue. Thanks again