After reading through some of the source code for PovRay, I discovered that
(I think) Sor's and Lathe's use cubic splines to calculate their points. But
after rendering the following scene, where each lathe uses the same point
setup as each sor, I am confused.

What method does sor use to calculate splines? (Picture at Bottom)

 #declare myLathe = lathe {
   cubic_spline
   7,
   <0, -5>, //Control Point
   <.8, -.3>,
   <.2, 0>,
   <.3, .3>,
   <.5, .5>,
   <.2, .6>,
   <0, 5> //Control Point
   sturm
   pigment {color rgb<1, 0, 0>}
 }

 #declare mySor = sor {
   7,
   <0, -5>, //Control Point
   <.8, -.3>,
   <.2, 0>,
   <.3, .3>,
   <.5, .5>,
   <.2, .6>,
   <0, 5> //Control Point
   pigment {color rgb<1, 1, 1>}
   sturm
}

object {myLathe translate x*1}
object {mySor translate x*-1}

object {myLathe rotate x*-70 translate <1, 1.5, 3>}
object {mySor rotate x*-70 translate <-1, 1.5, 3>}

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Attachments:
Download 'sorelathe.png' (23 KB)

Preview of image 'sorelathe.png'

Sor cannot bend back on itself. That is the reason for discrepancy.

 -Shay
Lieut_Data <lIe### [at] yahOOcom> wrote in message
news:3ca0dd7e@news.povray.org...

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