[x3d-public] NurbsPositionInterpolator example problem

[GPU Group]

CONFIRMED with freewrl, which console complains:
bad knot vector, replacing with:
[0]=0.000000
[1]=0.000000
[2]=0.000000
[3]=0.000000
[4]=0.500000
[5]=1.000000
[6]=1.000000
[7]=1.000000
[8]=1.000000
-Doug Sanden

On Thu, Sep 27, 2018 at 7:33 AM Andreas Plesch <andreasplesch at gmail.com>
wrote:

> The NurbsPositionInterpolator in the example at
>
>
> http://www.web3d.org/x3d/content/examples/Basic/NURBS/NurbsPositionInterpolatorExampleIndex.html
>
> does not have enough knots. The knot field only has 5 entries but it
> needs to have number of control points plus order entries, eg. 5 + 4,
> 9 entries, according to the last paragraph about the knot field in
>
>
> http://www.web3d.org/documents/specifications/19775-1/V3.3/Part01/components/nurbs.html#CommonGeometryFieldsAndCorrectness
>
> The example still works but in a limited fashion in NURBS supporting
> browsers because in the case of an incorrect number of knots, the
> browsers will compute a default uniform knot vector. The problem then
> is that the replacement vector is not guaranteed to span the 0 to 1
> range, or whatever range the original knot vector had.
>
> A working knot vector would be
> knot='0 0 0 .25 .5 .75 1 1 1'
>
> -Andreas
>
> --
> Andreas Plesch
> Waltham, MA 02453
>
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