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I was wondering - there is an option called "Fix Leaf Bones" when importing Collada format. Do you know, what exactly these Leaf bones are?

Also, if there is some expert able to tell me what the other options mean, Id much appreciate it!

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I'm not versed in armatures or rigging, nor an expert in that matter, but a little Google research yielded some results about it.

From the Makehuman bug tracker we can learn that apparently most applications and file formats don't store bone length information. This is normally not an issue, since bone length is rarely a needed information. In most cases it can be extrapolated from child bones.

A bone normally extends from its head until it's child's head, length is implicit and can be calculated from the distance between these two points.

It can however represent an issue for end bones, on the extremities of the armature, where no child bones are present.

On such cases an extra fake dummy bone can be created exclusively to represent the end of its parent, and no other function of its own.

These loose bones at the end of an armature are then called "Leaf Bones" by analogy of a tree leaf, I assume.

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    $\begingroup$ The point of leaf bones in other applications is to orient joints (rarely used for length). Last finger digit joints are more difficult to orient without a leaf bone, since they don't point anywhere. That's why leaf bones are added: to orient the penultimate joints. Blender has a tail on every bone, which is already a representation of the orientation of the bone (the combination of rotation and roll). $\endgroup$ – Leander Oct 4 '18 at 20:11
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    $\begingroup$ If the joints are oriented and the orientation is not going to be changed (and there are no complex constraints like IK), then the leave bone could be deleted without a problem. $\endgroup$ – Leander Oct 4 '18 at 20:12
  • $\begingroup$ Sounds like a better explanation than mine. Care to add your own answer? I shall delete this one $\endgroup$ – Duarte Farrajota Ramos♦ Oct 4 '18 at 22:52
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    $\begingroup$ I don't have collada import/export installed (on another app) to verify how the leaf bones are handled. I'll just leave these comments here, people in the future can search for joint orientation and will find plenty of resources. $\endgroup$ – Leander Oct 5 '18 at 7:33

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