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

[Bassam Kurdali]

Personally I think the great divide between armatures and objects- what
they can do/can't do , etc. is *mostly* bad, and occasionally but not
always prevents doing some things , at least nicely. So I'm all for
having the same interface (and hopefully shared code) for doing
interpolation/display etc. , so long as it doesn't cause some huge
problems.
I'd like direct access to quats, in some cases for backwards
compatibility, and in others because I'm used to doing certain
operations in quat. And knowing how bugger-all annoying rotations can
get, I can't help (pessimist) thinking that I'm going to need it.
It might be good to keep quat access for programmatic / scripting
purposes, too.

btw, Eulers in complex rotation cases can get quite, quite horrible an
unintuitive too ;)

> 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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