[Tugindia] psbezier

Ravi Gautam aol_gautam at rediffmail.com
Sat Aug 13 21:55:26 CEST 2005

Dear Manjusha,  
Thank you for the reply and kind advice. You are correct if one only needs to get the figure as a diagram. But actually I have to draw exactly a particular polynomial curve and I feel repeating a point twice will effect the polynomial of which we get the curve. I will probably use degree elevation and draw the (original) control polygon by a separate command.   

On Sat, 13 Aug 2005 Manjusha Joshi wrote :
> > > I am confused about psbezier. It takes more than 4control points without
> > > let me know if there is any solution to this problem.
> >
> > You cannot create a spline curve with less than the required number
> > of control points. The curve would be indeterminate!\
>One can always create a bezier curve for $n, n >= 2  $ points having degree of
>curve  $n-1$. So If there are 3 points, one can draw Bezier curve of degree
>And for 2 points bezier curve of degree 1 i.e. line.
>Only things is that \psbezier curve command is so defined that it requires 4
>points. Bezier curve for four points is always smooth i.e.  at least $C^1$
>curve. Therefore it is obvious to design bezier curve command for 4 points.
>And trick to obtain curve for  lesser number of point is, you use same command
>with repetition of end points, so effectively, there should be 4 points and
>since end points are repeating figure remains unaffected.

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