"Manuel Mata Rueda" <man### [at] yahooes> wrote in message 
news:4412bbe8@news.povray.org...
> Hi all.
>
> I noted a strange behaviour on cubic_spline when I define paths with the 
> spline  keyword. In previous version of Pov-Ray the first and last points 
> of the spline were to set the tangent of the second and the last but one 
> point. So the first and last "stretchs" between first-second and last but 
> one-last points were straight.
>
> In 3.6 version this is not this way so, why this behaviour on the new 
> version or am I wrong ?
>
> Thanks. See ya.

Hi Manuel,

With a cubic_spline the first and last points are just control points and 
don't actually get displayed. Whilst I haven't used cubic_splines much in 
POV-Ray my recollection is that POV-Ray has always been that way, so you 
don't get a straight line at the ends because you don't get any line at the 
ends, the shape starts at the second point and ends at the last-but-one 
point. As you say these control points form tangents to the start and end of 
the curve.

If you think you've found something odd with the behaviour of the 
cubic-spline in 3.6, maybe post a short snippet of SDL to illustrate your 
concern.

Regards,
Chris B.

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