Character forearms gets squashed after exported as animation.

[MarioCode]

Whenever I try to export animation(in FBX) made using SimpleIK rig with pole targets, the middle part of the forearms gets squashed.

Steps to recreate the bug -

1. Load Genesis 8 Character.
2. Use CustomShapes and Make SimpleIK Rig.
3. Animate the character, and possibly make the character hands reach the head level height.
4. Bake or Don’t bake to FK, Don’t think it matters.
5. Export the Animation to FBX.
6. Reimport the FBX file and the forearms are squashes like in the image.

So what I think is happening is something is rotating the hand bones during export of the animation.

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[Alessandro Padovani]

importer 1.7.4.2072, blender 4.1.0

I can’t reproduce the issue here, it probably depends on your export settings. Be sure you don't apply modifiers, only export deform bones, bake the animation. Another possibility is if you twist the hands a lot, in this case the forearms don’t follow properly, I reported the issue to Thomas with the solution but we don’t agree on the setup so this is a known issue. If you want to modify the rig yourself see #1708 for my setup.

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[Thomas Larsson]

As the tool tip says, the Bake to FK button doesn’t bake arms and legs, only other bones. It is intended for use with MHX, where you can bake arms and legs separately. Simple IK has buttons to bake FK and IK (the latter only approximately), but only for a single frame. Which would be annoying if you want to export an IK animation back to DS..

[Alessandro Padovani]

@Thomas it doesn’t matter, as the fbx exporter bakes bones and shapekeys so we don’t need to bake first, at least not for Simple IK since deform and FK bones are the same, while MHX and rigify require to bake to FK first.

[MarioCode]

@Thomas and @Alessandro, Thank you both for your answers, I think I found the issue, when I remove the Preserve Volume on the Armature Modifier it looks exactly like when I export it to FBX, so what’s happening is that Preserve Volume on the Armature Modifier is not getting applied properly during export, this is probably cause lForearmTwist and lForearmBend use the same weight near the forearm. I haven’t found any solutions yet.

[Alessandro Padovani]

The fbx exporter doesn’t support dual quaternion, that’s “preserve volume”, you simply have to set it back into the armature after importing. Or tell the game engine that the armature is dual quaternion, if it is supported. For example UE doesn’t. If there’s nothing to add we can close as invalid, since this is not a bug.

[MarioCode]

It only happens when genesis 8 character’s palm is head level and is facing the character and Preserve Volume is turned off in Armature Modifier. Thanks

[MarioCode]

Oh Alright, Thanks

[Thomas Larsson]

Even if the fbx exporter bakes the fk bones, it may still be useful to have a tool that bakes an entire fk animation from ik, e.g. if you want to export the animation as a pose preset. So I added a button for that in the Simple IK panel. I did some other changes to that panel to make it more useful. In particular, the Disable Lock and Limits button also appears in this panel, because locks and limits can ruin snapping.

[Alessandro Padovani]

For simple IK we can use the standard bake tool in blender, because the deform and FK bones are the same, there’s no need of an extra tool as it happens for MHX and rigify. Anyway I guess it doesn’t harm either. As for limits, in my opinion it is better to don’t import them in the global settings, when working with IK, rather than importing then disabling. Locks shouldn’t harm though, if they’re the same for IK and FK.

object > animation > bake action