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Re: Non-uniform b-splines

Posted by donkey on January 27, 2005 at 09:00:49:

In Reply to: Non-uniform b-splines posted by donkey on January 27, 2005 at 08:57:56:

That message didn't show up the way I wrote it. What I wanted to say was that I can't use values for the curve parameter, u, where:

u < U[3]

or

u < U[n+1]

: Hi,

: This question isn't really about subdivision, but maybe someone here still knows the answer. I'm also sorry if the question is stupid, since I'm pretty new to the whole thing.

: I'm trying to define and draw non-uniform b-splines. And it works out rather fine. With Cox-deBoor recursion I can generate both uniform and non-uniform curves, closed or open. The problem comes with the parameter value.

: If I have a knot-sequence U {0, 1, 2, .., n+4} and some control points P[0], P[1], .., P[n] for cubic spline-segments, I can't use parametervalues, u, where u U[n+1]. When I do, the resulting values goes towards 0 for every control point. The visual result is for every set of knots and control points a curve that starts and ends in origo.

: Is it supposed to be like this, or am I doing something terribly wrong (perhaps I've not implemented the recursion algorithm correctly)?



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