[x3d-public] NurbsPositionInterpolator example problem

[Andreas Plesch]

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