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

[Jeffrey H]

I wouldn't say there is any "best practice" when orienting your bones aside
from maintaining consistency. Yes, it can make it easier to understand and
mentally visualize when it's explained over text, but when working it
really doesn't matter. The key over everything else is consistency. For
example: when rotating fingers, have ALL the fingers rotate in the same
direction when X is increased or Z is decreased or whatnot. Or when using
FK arms, make the elbow and shoulder rotate in the same direction when X is
increased, etc.

What I've found in my rigging experience is that axis rotation is largely
dependent on Euler rotations and rotation order, not quaternions. For
example: I usually make my elbows rotate on X+ because it's the inner-most
Euler calculated (or if you reverse the rotation order, the last
calculated, leaving the arm cleanly rotatable along its long axis).

>From an animator's point of view, it does not matter what axes are where,
just as long as they are consistent: mirrored bones should have mirrored
rotations as well; bones should rotate in the same direction if they're
part of the same limb (or spine or neck...), etc.

I'm sure some would disagree with me, especially newcomers, but as an
experienced animator in Blender and Maya with experience in rigging in
both, that's how I see it. I've never come across an issue regarding axis
orientation. The only problem I ever have with rigs is the rotation order,
which is simple enough to change to fit the situation that it doesn't
affect how I work.

If you haven't already, you should check out Nathan's Humane Rigging: Youtube
Playlist <https://www.youtube.com/playlist?list=PLE211C8C41F1AFBAB>
If I recall correctly, he goes over bone rolls in the bouncy ball rigs.


On Tue, Jan 7, 2014 at 4:44 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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>



-- 
Jeffrey "Italic_" Hoover
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