Dual Quaternion Skinning Joint scaling issue!

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  01 January 2014
Dual Quaternion Skinning Joint scaling issue!

Well , so I am working with the weight blended skinning method for my character to be able to paint DQ skin weights around the knees and the arms, and classic linear for the rest of the body.
The rig has stretchy arms with segmented joints and IK Spline handles for the wrist roll and elbow roll.
The problem starts coming the moment the arms stretch. There are no problems while stretching in classic linear skinning, but the areas I paint DQ weights start deforming
(For some reason I am unable to attach an image to this post).
I am using Maya 2014 Student version.

Please if anybody knows the solution to this, help me out :/
  01 January 2014
Yes, DQ seems to have issues with joint scaling. For your stretchy ik, maybe you can switch to translation instead of scaling. If all you are doing is adjusting the chain length to follow the handle, then translation will achieve the same result, and will not break the DQ.

  01 January 2014
Hey djx! Yeah I had figured out the scaling issue, but isn't there something that can be done without changing the rig itself?

I have a translation based stretchy system in the legs, I am using setDrivenKey function to set keys on the joint translation at the normal and double length of the overall leg. It seems to be working fine. But for the arms I was calculating the stretch factor from the curve length of the ikSpline curves.

I guess it shouldn't be a problem to make one for arms as well, but if there would be a way with joint scaling itself that would save me quite some time.

Thanks a lot for the reply
  01 January 2014
Ah well I couldn't find the solution to the DQ skinning issue with joint scaling, but with a little bit of maths, I have converted the scaling-based stretchy system into a translation-based one
Still if anyone out there knows a solution to this issue I am still curious to know it!

Thanks djx for the input
  01 January 2014
DQ scaling/skinning issues are a huge pain when they come up. (Try using influence objects!)

But in a nod to the issue Maya devs included the Weight Blended skinning method.
It's the third option in the skinning method select-o-box. This offers the ability to paint where on your character you want to use DQ skinning and where you want to use Classic Liner skinning. While it would be great to have nice DQ deformations on your stretchy arms...it can let you use it everywhere else and not have to re-make your rig.

Of course, now that you have rebuilt your rig, you have a much better rig setup that allows you to use DQ skinning all over. So, rock it out.
  01 January 2014
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