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Ik spine explodes when max stretch above 1.5


#1

Hello,

We’re having a problem where if you raise the max stretch above 1.5 and then addTranslation and Rotation in "spine_C0_ik1_ctl’, any geometry that is skinned to the spine quite literally explodes. Especially if you translate in Z or X. Has anyone else encountered this? We are using mGear 3.03.

Thank you,
Alicia.


#2

Yep, just checked and that happens on my side too. Also, I just tried slowly scrubbing maxstretch and when I hit a certain value near where it looks like the spine scales to zero, Maya froze. So I am guessing there is some division-by-zero problem or similar.

Maya 2018.5 - Windows 10 - mGear 3.0.3 - spine_ik_01 module.

Also on spine_C0_root you have some stretch profile options. As a quick fix, you might be able to find better values that don’t hit that singularity. But when I was scrubbing those attributes while the spine was over-stretched, again Maya froze. Editing those attributes when the spine isn’t stretched doesn’t seem to cause any problems for me.


#3

Hello @Alicia @chrislesage

Yep I also can reproduce the issue. It is related to the initial configuration values

Setting the stretch min value to -.999 will fix the issue
image

I will add add something to avoid this in the future

Cheers,
Miquel


#4

Thank you Miquel and Chris!

So I tested out change the ‘spine_C0_root.stretch_2’ attribute to -.99 and I find that this fixes the exploding spine, but it does cause warping in the spine when ‘spine_C0_ik1_ctl’ is translate forward in +Z while being stretched and rotated.

I found that a lower value (~0.9) fixes this issue and seems to have a more stable result

image



(excuse the simplistic example, I can’t show the model that I’m working on)

Thanks again for the help and such a quick response,
Alicia


#5

Thanks @Alicia for the feedback I will check this ASAP. We are also using this component in production.

Best,
Miquel


#6

i saw this behaviour also in the leg component, also in v2.5.xx. the legs were exploding when the ik stretching was envolving…


#7

@soulcage thanks for the head up on this

I have log it here: https://github.com/mgear-dev/shifter_classic_components/issues/41


#8

We had this same issue for the legs. My artist looked into it and found that the wrong axis was hooked into the stretch. ( we were on v 1.03 at the time) we haven’t seen this issue on the legs for version 3.03. We just did a maya and unreal stretch test yesterday and everything seemed to hold up. I’ll keep you guys posted if we come across it again.