I came back to this after watching some of the final lessons because the Bone Roll feature in Blender confused me a little. In the middle of the Crane Arm tutorial Wayne changes the orientation of the claw bones 90 degrees along it's own axis. When I tried to do the same thing (I probably didn't pay enough attention) I tried to use the rotation tool in Blender, but no matter what transform space or Pivot type I used, I could not rotate the bones around its own Y axis. Eventually, I figured out that I could change the roll angle by typing in the Transform panel. Came back here and rediscovered CTRL-R for Roll. Anyways, does anyone know if there is a specific reason why Blender won't simply let you use rotation around the Y to roll?
Actually, now that I think about it, what I did in the Crane Arm tutorial was to switch to pose mode, rotate the bone around it's Y axis there, apply the transform to rest pose (Ctrl-A), go back to edit mode. A bit of a workaround really. I still don't understand why Blender is made so I can rotate around Y in Pose mode, but not in Edit mode where instead there is a separate Roll function.
Roll Dem Bones by Five Finger Death Punch
...for when operations in Blender aren't going as planned...
Change transform orientation(press comma) from global to normal. Why? Global is the world's axis. Local is the armature's axis. Normal is the bones axis. Now when you press R then an axis it will be the bones axis that it constrains rotation to.
Hi Markus MarkusSchille ,
Good questions, but if you compare this to a Mesh, then a Bone is similar to an Edge. Have you ever tried to Rotate an Edge that way in Edit Mode?
The Edge's Normal (Z-Axis) is pointing away from the World Origin, R, Y won't change that.
Bones are more powerful in that they have a Roll in Edit Mode, but it's not the same as Rotating along its Y-Axis.
Sorry, I just remembered that the rotation on y doesn't work in edit mode with Blender at all. There was a branch of Blender that did that and was part of the animate all project or it might have been one of the Google Summer of Code (GSoC) projects. The reason is because the roll affects the rest position of the bones and is a different RNA/Data. In other words, it's a completely different operation. More technically accurate way to say it is that you are rotating the joint to it's starting/mid twist position. I don't know if I explained it very well. It also helps to look up orientation vs rotation. Simply put orientation is the point where you start before you rotate. Rotation is changing the orientation. This Video from the Humane Rigging series explains it better than I can: https://www.youtube.com/watch?v=SZE_KOjreAs&list=PLE211C8C41F1AFBAB&index=12