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Squash Component Vs IK or FK Spine doing strange things

Howdy all,
I’ll try to explain this as best as i can and include a link to the maya file so anyone can see the issue.

https://drive.google.com/drive/folders/1qFCNvsVfK4oz5sOgwH3In7NAHhmGP0Gt?usp=sharing

(its a simple file with 2 guides and 2 rigs that demonstrate the issue described below)

When building a rig that has the “Squash” component as a parent to a “FK_Spine” component that has any “Leg” component attached. Things behave in a predictable manner.

But.

If you build the same set up but swap out the “FK_Spine” for any of the IK spines even the new Epic ones. when moving the squash controller up and down it scales the leg off the ground when they are in FK mode… even if the squash component is at the root of the character. Is there any way to fix this?

Also regardless of the type of Spine component you have, if you attach a “Neck” component to the “Spine” when moving the Squash controller up and down it quashes and scales the Neck in the opposite axis from the the rest of the rig.

I am on Maya 2020. and using mGear 4.0.3

Thanks agian!

Has anyone had a chance to look into this? Any and all help would be appreciated.

Thx.

I’ve taken a look, but I’m not familiar enough with the differences in how they are supposed to behave, vs. how they are behaving. Sorry.

In your demo, when I move the squash control up at the top, I see the spine stretches in a completely different way. And the node that the legs are parented under have different non-uniform scale values.

I’m not sure if that is the design of the component or a bug. If you isolate the behaviour as a bug, please let us know. Otherwise, if I were you, I’d just focus on finding a workaround.


When I rig I always have a “hips” controller in the middle between my spine and legs. And if you did that, you could potentially interrupt the scale/skewing issue by scale constraining the hips to a more stable control, like the body.

I also always have a “chest” control at the top of the spine, so anything above the spine (neck, shoulders, etc.) have that as a parent. When I export to Unity, I need to do at least one of these workarounds:

  • I sometimes put “chest” under my world joint so that the head and arms don’t skew with the spine, since Unity does not handle segment scale compensation in the same way as Maya. Sometimes this is an unacceptable skeleton, depending what they are doing with the skeleton in-engine.
  • Or I force uniform scaling on all the nodes

Whether you are using Unity, Unreal or not using a game-engine at all, the principle remains: Have an intermediary joint between the spine and other body parts, whose scaling you can control or override. It might give you more options.

Anyway, sorry I can’t be more help. Maybe that gives you an idea for a workaround.

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The spine wasn’t behaving the same way because i think i didn’t turn off uniform scaling on the “FK_Spine” guide. I changed that now and regenerated it.

But my issue is NOT with the spine at all (well sort of). Both rigs are essentially the same except for the type of spine used. Except one of them lifts the FK legs off the ground when being scaled.

On in this example the rig on the left is using the Epic Meta Human Template (i just deleted the arms off) and the example on the right has the exact same set up EXCEPT for the spine.

The squash controller is parent of the body controller that is parent of the spine in both set ups.

Also notice the HEAD that is scaling in a totally diffrent axis then the rest of the body.

here is the link to the file :

https://drive.google.com/drive/folders/1qFCNvsVfK4oz5sOgwH3In7NAHhmGP0Gt?usp=sharing

20211123_165315

Hello! I am following this thread. I will check this issue ASAP :slight_smile:

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