[Bf-animsys] Best practice for "how to setup Bone rolls" ?

[Campbell Barton]

Hi Gaia, after reading your mail I realized we don't have a good way
to calculate roll based on the bones relative angles.

So I went ahead and added this in (New options for recalc roll X/Z Tangents).

https://developer.blender.org/rB0213a43562cd60fa6e20535c5851733f47f20da4


Also I asked about the best default dominant axis to use for joints here.

http://blender.stackexchange.com/questions/6061/rigging-convention-for-limb-joint-dominant-axis

On Tue, Jan 7, 2014 at 10:44 PM, Gaia <gaia.clary at machinimatrix.org> wrote:
> Hi;
>
> Over the last few days i tried to understand why the bone rolls for a
> given Armature have been chosen as they are. I was looking for some sort
> of "best practice for Bone roll"  in the Blender wiki or at
> blenderartists.org. I also looked at Blender's
>
>      Armature -> Bone Roll -> Recalculate Bone Roll
>
> and tried to make sense out of what is calculated there.
>
> Since i could not find any clear how todo descriptions, i just collected
> what i found into a list of rules of thumb as follows. (And i do not
> know for sure if the rules make sense after all, they sound somewhat
> reasonable though)
>
> - Determine the main rotation axis for each bone and consistently align
> the bone roll (either X or Z) to this axis
> - For horizontal bones match Bone-Roll-Z with global-Z, and for vertical
> bones match Bone-Roll-X with global-X
> - For all bones ensure that bone roll Z is in the same plane (i am not
> at all sure about this in particular)
> - Use Bone Roll X for up/down movements, like fingers up/down (when
> looked from the side)
> - Use Bone Roll Z for sideway movements, like finger left/right (when
> looked from above)
>
> Now i'd like to verify that these finds make sense. And then add a "Bone
> roll best practice" chapter somewhere below
>
>      http://wiki.blender.org/index.php/Doc:2.6/Manual/Rigging
>
> However it would be nice to get some feedback and advise from a "rigging
> specialist", even a few lines of "raw documentation" that go beyond "I
> believe its so and so..." would be very helpful.
>
> cheers,
> Gaia
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-- 
- Campbell