[x3d-public] computed orientation_changed output

[Andreas Plesch]

I think the issue is that the spec. only defines the toVector (as the
tangent) but is silent on the fromVector. It is a reasonable assumption
that the fromVector is implied as 0,0,-1 ("forward") and most
implementations will do that. But in theory it could be any vector.

An additional ambiguity is that there are two possible rotations from a
vector to another vector. One is using the inverted axis of the other. But
as long as these rotations are only used to actually be applied as
rotations, this may not matter as both lead the same result.

Andreas

On Sat, Aug 31, 2024, 6:14 AM Holger Seelig <holger.seelig at yahoo.de> wrote:

> It is possible to calculate a rotation from fromVector to toVector, but
> these rotations have an arbitrary upVector.
>
> And yes, it would be better to have a defined upVector to make these
> rotations stable.
>
> Holger
>
> --
> Holger Seelig
> Leipzig, Germany
>
> holger.seelig at yahoo.de
> https://create3000.github.io/x_ite/
>
> Am 30.08.2024 um 23:45 schrieb Patrick Dähne <pdaehne at gmail.com>:
>
> Unfortunately, it is not possible to implement
> NurbsOrientationInterpolator because it is not specified how to calculate
> the „up“ vector (the tangent of the curve only specifies the z axis, but
> neither the x nor y axis of the local coordinate system). The same applies
> to any other hypothetical „xOrientationInterpolator“.
>
> Bye,
>
> Patrick
>
>
>
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