Mike Williams <nos### [at] econymdemoncouk> wrote:

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

degree, control point and knot partition are tipical parameters used to
describe a spline curve...

> What is a degree?

the degree of a spline is the maximum degree of each polinomial
interpolation functions that define the spline...linear spline has degree
1...quadratic spline has degree 2...etc

> Why do your control points have four dimensions rather than three?

ignore the fourth number...

> What is a knot partition?

It's a set of number that specify the subdivision of the spline's parametric
domain...

In povray, referring to spline statement..

spline {
     linear_spline | quadratic_spline | cubic_spline
      -1, < 0, 0.5, 0.0>,
    -0.5, < 0, 0.2, 0.4>,
    0.01, < 0, 0.2, 0.2>,
     0.5, < 0, 0.4, 0.4>,
       1, < 0, 0.0,-0.6>
   }

the degree is specified by the spline's type...
-1,-0.5,0.01,0.5,1 determine the knot partition...
< 0, 0.5, 0.0> , < 0, 0.2, 0.4> , < 0, 0.2, 0.2> , etc... are control points
coordinates...

I hope you can undertand better my problem now...
Leo

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