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

[Nathan Vegdahl]

Oh, I should also say: the choice of x vs z axis as the "primary" rotation
axis is arbitrary.  I choose x because it's the first letter in "xyz".  But
z is just as good.  What matters is consistency within the rig (or within
the project if it's a larger project).

--Nathan
On Jan 8, 2014 8:05 AM, "Nathan Vegdahl" <nathanvegdahl at gmail.com> wrote:

> Hi Gaia,
> The main rules-of-thumb that I try to follow are:
> - The x-axis should be the "primary" axis of rotation for any given
> control.
> - Rotation in the "primary" direction on the x-axis should result in a
> positive rotation angle (meaning that if it were euler, the x component of
> the rotation would be positive).
> - For bones that are free-floating and/or don't have any particular
> relationship to other controls (the root control is a good example), align
> all of their axes with the world axes.
>
> In the first two rules, "primary" is often subjective or ambiguous,
> depending on the control, so you just have to use your best judgement and
> experiment what it feels like to use it as an animator.
>
> It's important also to note the reason for doing any of this at all.  In
> all 3d animation software, keeping bones aligned well helps keep the rig
> better organized for the rigger.  It's also important for animators when
> e.g. working in the f-curved editor.  But in Blender it's particularly
> important for animators, because one of the major interaction models for
> tranforms is via hotkeys, using the x, y, and z keys to specify axes.
>
> --Nathan
> On Jan 7, 2014 3:44 AM, "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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>>
>
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