Non uniform scaling of individual elements in hierarchical structures

#1

There is one big thing that prevents me from finishing a big part of my auto rig right now, and that is “Non uniform scaling of individual elements in hierarchical structures”. It produces skewing.
If a parent object is scaled non uniformly, then any child object not placed at it’s parents pivot and not being a dot (that is, any shape not consisting of a single point in space) will become skewed if rotated. Simple as that.
Maya’s joint’s have something called scaleCompensate, an option that forces the joint to attempt to compensate for it’s parents scale by counter-scaling itself. This works well with uniform scaling, but non-uniform scaling together with child-rotation produces the same skewing. This makes it very difficult to use clean hierarchical end-chains (joint chains for skinning and muscle deformation).
If I allow myself to use split joint end chains, or end chains that have one extra child joint (positioned at the same place as it’s parent, letting this joint receive scaling data and letting this joint influence all of the skinned elements for that part instead of it’s parent) then this will not be a problem.
I don’t know if I want to go in that direction though. What is the pros and cons of a split-joint skin setup versus a joint-chain? Is there any solution for the above mentioned problem that can prevent me from having to split it up in the end? Do I have to worry at all about problems that possibly may or may not occur if I use a split-joint setup or should I just go ahead and do it?

Thoughts, help or random reflections on the case is greatly appreciated.

Cheers!
Gabriel

#2

Do you need to keep the scale values? Why not just do a Reset Transformations on the Scale? That gets rid of the skewing.

#3

it’s much better to avoid scaling in joint hierarchy and get around with translate instead. At least keep the main hierarchy skeleton scale-free. It causes so much problems upstream.

#4

I agree with uiron and to your original question, if you want non-uniform scaling go with the split method as you called it.

#5

I don’t think you have to do a split hierarchical structure. what you need is another set of joint to use only in set up that will stretch as needed and feed the direct values to the joints they are cloned after. Their are systems that use constrains as well to nullify the local value changes of a parent, leaving their children editable. If you have any questions I may be able to make a short demo of the idea.

#6

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