[x3d-public] default interpolation keys

[Leonard Daly]

Andreas,

>
>     This is a very reasonable suggestion. As you point out, there would be
>     no way to get an empty key field except when keyValue was also empty.
>
>
> The only situation I can vaguely imagine when empty key and keyValue 
> fields would be useful is an initial state which does not want to be 
> immediately changed to a functional, fully populated interpolator. But 
> this would be likely a misuse since activation like this should be 
> done more explicitly.

Yes, there should be an 'active' field that turns an interpolator 
on/off. Or better, bundle the TimeSensor functionality needed for 
interpolation with the Interpolator. This would include the regular 
controls for on/off/pause/resume/etc.


>     ...
>     I haven't looked, but I suspect A-Frame uses TWEEN to do the
>     interpolations....
>
>
> Yes, A-Frame uses TWEEN. The proposed default key value would 
> correspond to the default TWEEN behavior. I had raised an issue with 
> Tween here to discuss keyed animation:
> https://github.com/tweenjs/tween.js/issues/352
>
> As discussed there it turns out that by using custom (piecewise) 
> interpolation or custom easing it is already possible to do key frame 
> animation with Tween. This is what I do for the A-Frame keyframes 
> component. So I do not think there will be changes to Tween although 
> the maintainer expressed some interest.


I should review that issue. From what I read of the docs and code, it 
would be difficult to get non-evenly spaced keys. The developer would 
need to calculate the position along the path for evenly spaced points 
to make that work. Yes, it could be done with varying durations and 
chaining, but it would start to get real messy with easing and 
non-[piece-wise]-linear paths.


-- 
*Leonard Daly*
3D Systems & Cloud Consultant
LA ACM SIGGRAPH Chair
President, Daly Realism - /Creating the Future/
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