"LanuHum" <Lan### [at] yandexru> wrote:
>
> To receive acute angles in cubic_spline it is necessary to duplicate control
> point several times:
>
> <1,0,0>
> <1,0,1>
> <2,1,3>
> <2,1,3> //repit
> <2,1,3> //repit
> <2,1,3> //repit
> <1,0,2>
>
> I found the bad solution.
> To model nurbs, to write down as cubic, to use meshmaker.inc for creation of
> obj, to load obj into scene, to see result
> Our dear friends-developers will laugh, but so far it is the only thing to do.
> :)  :(

Uh,... alright, thanks. This is a good idea to make an acute angle in cubic
spline truly. But it is not enough to finish the converting.
Here I put an image which I downloaded from the Wikipedia to explain.

When we place a series of point, the way of drawing cubic spline is connecting
each point and its following point by a 3rd order polynomial, ..uh, let us give
an example, just say that the curve between p1 and p2. When we draw this curve,
what we use is the position of node p1 and p2, but we still do not tell the
direction of the nodes on the curve, right?
So, in a bezier spline, it uses two additional control points to collect the
information; in a cubic spline it uses some other nodes p0 and p3 to achieve the
same goal.
Now you can realize what the problem is, it uses some other nodes p0 and p3 to
complete the condition of direction.

And This will lack the form it is.

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