[Bf-funboard] Euler for animator, Quaternions for Blender

[Robert Ives]

> > in my recollection, animation master allowed selection between multiple
> > curve types for display ( quats, eulers, axis angle maybe or spherical)
> > and independently for interpolation.. so you could select euler
> > editing/display and quaternion interpolation.

I also checked out the programs at work. Motion-builder has an Quaternion/Euler
option per object.
Maya has a variety of options as a scene preset or marked curve can be
converted.
I must say I only use the first.
Pasted direct from the help file:

Independent Euler-Angle Curves:

      Calculates the rotation using three angles representing
rotations about the X, Y, and Z axes, and an order or rotation. In
this mode, the curves that define the rotation for a given node are
represented in Euler-angles, interpolation is performed on each curve
independently in Euler space, and keyframes may occur at your
discretion—they are not synchronized with the other sibling rotation
curves at the node. You can also animate a single rotation ordinate.
This is the default setting.

Synchronized Euler-Angle Curves:

      Creates curves that have keyframes on sibling curves locked
together as in Synchronized Quaternion Curves but the interpolation
between keyframes in performed in Euler-space.

      It's useful to keep rotation keyframes synchronized because
rotation is a composition of the three separate rotate values.
Deleting just one key on a curve can have a dramatic and unexpected
effect on the interpolation.

Synchronized Quaternion Curves:

      Calculates the rotation interpolation using three orientations
about the X, Y, and Z axes, and an angle of rotation. The
interpolation between keyframes is defined using quaternion
interpolation. Keyframes on related curves are locked together. When
you add, delete, or move a keyframe on one curve, the corresponding
key is also updated in the sibling curves.

> One question, though -- is this desirable for all objects, or just
> bones?
I think the choice of which Animation calculations should be
consequent, to stop confustion
making this a user preference, rather than one way for objects and
another for bones. But maybe this is a major fix?

> One other question from a user standpoint -- if we did this and let the
> animator work with Euler curves and values, would you ever need direct
> access to the quats? I'm thinking not. Opinions?
An option to switch between different calculations modes (As above)?
Maybe in the preference window?




On 5/10/07, Roland Hess <rolandh at reed-witting.com> wrote:
> Glad the animation system is finally getting some love and attention!
>
> My initial thoughts and research lead me to think that what we do is to
> store and maintain rotations as eulers in the Ipos, and convert to quats
> behind the scenes for interpolation. You're right that quat->eul is not
> discreet. Personally, I don't think this would be that hard to do.
>
> One question, though -- is this desirable for all objects, or just
> bones? As you know, right now only bones use quats. One place to look in
> the code (and I guess that's more for me, than you guys :) ) is the
> joint limiting in the IK code. It uses Euler constraints on Quat
> rotations, so there almost certainly has to be some kind of process
> already in place there to deal with it.
>
> One other question from a user standpoint -- if we did this and let the
> animator work with Euler curves and values, would you ever need direct
> access to the quats? I'm thinking not. Opinions?
>
> Roland -- harkyman
>
>   > in my recollection, animation master allowed selection between multiple
> > curve types for display ( quats, eulers, axis angle maybe or spherical)
> > and independently for interpolation.. so you could select euler
> > editing/display and quaternion interpolation. Don't quiz me on how this
> > works though- I don't think that quat to euler is one to one, so I've no
> > idea how am or other apps handle it internally.
> >
> >>         Following up a discussion in Comitters list:
> >>
> >>         I also found myself struggling with Quaternions when
> >>         retouching
> >>         animation and agree that having a more understandable
> >>         interface for
> >>
> >>         animators (let's say, using Eulers instead) and let Blender to
> >>         manage
> >>         internally Quaternions would be a great improvement in
> >>         workflow.
> >>
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-- 
________________

Robert Ives.
Character Animator