Wasn't it LEO_BOLOGNA who wrote:
>
>I know every information of a spline:
>- I know the degree (2)
>
>- I know the coordinates of each control point (9 in total)
>0 3.000000e-01 0.000000e+00 1.000000e+00
>3.000000e-01 3.000000e-01 0.125000e+00 7.071070e-01
>3.000000e-01 0 0.250000e+00 1.000000e+00
>3.000000e-01 -3.000000e-01 0.37500e+00 7.071070e-01
>0 -3.000000e-01 0.50000e+00 1.000000e+00
>-3.000000e-01 -3.000000e-01 0.625000e+00 7.071070e-01
>-3.000000e-01 0 0.750000e+00 1.000000e+00
>-3.000000e-01 3.000000e-01 0.875000e+00 7.071070e-01
>0 3.000000e-01 1.000000e+00 1.000000e+00
>
>- I know the knot partition (12 knot in total)
>0.000000e+00
>0.000000e+00
>0.000000e+00
>2.500000e-01
>2.500000e-01
>5.000000e-01
>5.000000e-01
>7.500000e-01
>7.500000e-01
>1.000000e+00
>1.000000e+00
>1.000000e+00
>
>How should I combine (from a mathematical point of view) these information
>to obtain the same spline on povray?

I've no idea what any of your terminology means.

What is a degree?
Why do your control points have four dimensions rather than three?
What is a knot partition?

-- 
Mike Williams
Gentleman of Leisure

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