[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.

I haven't looked, but I suspect A-Frame uses TWEEN to do the 
interpolations. TWEEN automatically provides evenly spaced keys when 
given multiple keyValues. I was planning on working on an upgrade for 
that sometime this fall. Please let me know if you are going to make 
modifications to TWEEN.

Leonard Daly



> The default key field value is [ ], empty.
>
> http://www.web3d.org/documents/specifications/19775-1/V3.3/Part01/components/interp.html#X3DInterpolatorNode 
>
>
> recognizes the validity of an empty key field, which then means no 
> events are generated and no interpolation happens.
>
> Is that behavior useful for any situation ? A serious question, 
> perhaps for prototypes somehow ?
>
> I am developing an Aframe equivalent to interpolation nodes 
> (https://github.com/andreasplesch/aframe-keyframes-component) and 
> weigh other default key values.
>
> Specifically, I am leaning towards a default which provides constant 
> intervals for keyValues. If there are 5 keyValues, the default keys 
> would be [0,0.25,0,5,0.75,1]. This is what most commonly may be the 
> expected behavior from an interpolator. Given n keyValues, default 
> keys are [0/(n-1), 1/(n-1) .., (n-1)/(n-1)].
>
> The benefits of such a default are least surprise, and more concise 
> scenes.
>
> The drawback is backwards incompatibility although I have not seen a 
> scene which uses the default key field value.
>
> My goal is to raise a better informed specification comment as I feel 
> there may be more to consider.
>
> Any comments are very welcome,
>
> Andreas
>
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-- 
*Leonard Daly*
3D Systems & Cloud Consultant
LA ACM SIGGRAPH Chair
President, Daly Realism - /Creating the Future/
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