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"Recalculate Bone Roll > Cursor" doesn't seem to work as expected
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System Information
Windows 10 Pro

Blender Version
Broken: 2.77a

Recalculate Bone Roll > Cursor" doesn't seem to work properly all the time

Exact steps for others to reproduce the error
After praising the function here last night, I encountered several cases where the function fails to align the roll of bones properly to the 3D Cursor.

Here's a demonstration of where it behaves in an unexpected way.

The first time I orient the roll of the selected arm bones to the 3D cursor, when I align my view along the primary axes of both bone, you can see that the two X axes aren't really pointing to the 3D cursor as well as they could (taking into account the limitation due to the fixed Y axes of course.

But more visibly, when I then position the 3D Cursor behind the elbow, so that the bones' roll should by my expectation flip by around ~180 degrees when oriented to the 3D Cursor, they merely rotate by ~30 degrees or less.

Now either I'm misunderstanding the function or it's bugged. Jason van Gumster suggested I report this, so here we go.

Here's a scene file:

Event Timeline

I can confirm that the behavior isn't quite as I would expect it to be. For instance, in the example .blend file, in order to get the bones' z-axis to point in the positive Y axis, I need to put the 3D cursor either very low in the global z-axis or quite a bit into the negative (crossing the center line) in the x-axis. The attached images should show that.

Sorry but why was this set to "Resolved" without any further comment?
@Campbell Barton (campbellbarton): Did you check the project file I attached?

EDIT: Never mind, I only now saw the commit. Thank you!! :)


Campbell found the root of your issue, committed a fix and pushed it to master. When he pushed it with "Fix T..." , the system recognizes the reference and closes the issue. So compile Blender and test it or just wait for the buildbot build to be updated and test it there.

Best, Thomas

Awesome, thank you. I edited my previous comment.
Didn't see the commit at first, sorry for the confusion.

@Chris Offner (chrisoffner3d) I understand you, it is not in every app development, that you get a bug quickly fixed like in Blender. Don't stay here you will be spoiled ;)