Document how to fix eInheritRSrs error.

[robertlong]

I've been looking into the transform inheritance types and can't quite figure out what this inheritance type means or how to avoid it. Could you document this?

[zellski]

It's tricky stuff, and to some degree we're out of the luck. They are all valid in FBX, and I assume any compliant FBX viewer is supposed to handle them correctly. But only the vanilla one can actually be expressed by glTF in a way that survives into any kind of dynamic environment.

• eInheritRSrs is what we're all used to: the effective local transform consists of applying the parent's global rotation and scale, then local rotation and scale.
• eInheritRrSs switches up the order so the local rotation is applied before any scaling is done. Mostly this makes my head hurt.
• eInheritRrs literally ignores global scale, meaning the sub-hierarchy of the scene graph that hangs off the node in question becomes immune to any scaling done above it.

All three of are in active use. Maya pretty reliably seems to output eInheritRrSs for root nodes, eInheritRSrs for most regular nodes, and eInheritRrs specifically for the feature called 'Segment Scale Compensate'. There is further information on this here: https://knowledge.autodesk.com/support/maya/troubleshooting/caas/simplecontent/content/turning-segment-scale-compensate-maya-how-to-make-maya-rigs-play-nice-unity.html. There's just nothing we can do to salvage a model with this inheritance structure; we simply have to communicate to artists that they are better off disabling this feature.

In practice, eInheritRrSs seems to cause no trouble; probably because I only see it appear at the root node, where of course there's no inherited parental transform to worry about.

I'll see about documenting all this better. I might add a section in the README, or save it for a future when we have an actual set of documentation pages.

Finally, heh, as I eyeball the FBX2glTF code, I think there's an embarrassing bug. We warn about eInheritRSrs, not about eInheritRrSs. That's the wrong way around, and I'll fix it.

Meanwhile, does this all make any sense? Does it rhyme with what you've read up on & seen elsewhere?

[zellski]

Actually, that's another improvement: no reason to warn against eInheritRrSs when parsing the root node. That'll get rid of a pointless, common warning.

[zellski]

Leave open for documentation change.

[Alexxkrehmen]

Hi, I'm trying to convert and import a FBX file into blender using FBX2glTF version 0.9.7, and I have this warning :

Warning: node /RootNode/Bunnyx uses unsupported transform inheritance type 'eInheritRrSs'. (Further warnings of this type squelched.)

Once opened into blender, the rig structure looks ok, except for the scaling and position of the root bone (Bip_Bunny) which is offseted by 85m on the Y axis in Pose Mode and Z axis in Edit Mode. Its scaling is 0.01 in Pose mode too.

I'm trying to figure out how to fix it by hand (this is more a blender thing) but having the converter fixing it from the start would be great ;) Bunnyx.fbx.zip