Hello, 
I was playing a little bit with the paragraph in the official
documentation explaining quadratic splines for lathe objects, and I have
encountered was seems (to me) to be a bug with the orthographic camera
(see scene source below).I'm using PovRay 3.1g (official) and MacMegaPov
0.6 on a Macintosh, and the pb appears in both.

Can anybody else confirm this on other platforms? Or is it a well known
problem? Or is it me who is doing something stupid ?

Cheers,
Stephane.


 // this file seems to demonstrate a bug involving orthographic cameras
 // and lathe objects with quadratic splines
 // Bug shows up both in 3.1g official and MegaPov 0.6 unofficial
 
 
  #include "colors.inc"


// the offending camera
  camera {
    orthographic
    up <0, 5, 0>
   right <5, 0, 0>
   
  // the following line was "location <2.5, 2.5, -10>" in the
documentation
  // changing the "2.51" a little bit changes the appearance of the bug.
  location <2.5, 2.51, -10>
  
   look_at <2.5, 2.5, 0>
  }

// use the following camera to see how the lathe object is suppose to be
/*
 camera {
   angle 10
   location <1, 9, -50>
   look_at <0, 2, 0>
 }
*/

 light_source {
   <20, 20, -20> color White
 }


 background{Gray50}

 #declare rayon_angle_plateau = 1.1;

  /* set the control points to be used */
  #declare Brown_Point = <0,0,0>
  #declare Red_Point    = <rayon_angle_plateau, 0.50, 0>;
  #declare Orange_Point = <1.75, 1.00, 0>;
  #declare Yellow_Point = <2.50, 2.00, 0>;
  #declare Green_Point  = <2.00, 3.00, 0>;
  #declare Blue_Point   = <1.50, 4.00, 0>;
  #declare Tan_Point = <0.0, 5.00, 0>

  /* make the control points visible */

  cylinder { Brown_Point , Brown_Point - 20*z, .05
    pigment { Brown }
    finish { ambient 1 }
  }
  cylinder { Red_Point, Red_Point - 20*z, .05
    pigment { Red }
    finish { ambient 1 }
  }
  cylinder { Orange_Point, Orange_Point - 20*z, .05
    pigment { Orange }
    finish { ambient 1 }
  }
  cylinder { Yellow_Point, Yellow_Point - 20*z, .05
    pigment { Yellow }
    finish { ambient 1 }
  }
  cylinder { Green_Point, Green_Point - 20*z, .05
    pigment { Green }
    finish { ambient 1 }
  }
  cylinder { Blue_Point, Blue_Point- 20*z, .05
    pigment { Blue }
    finish { ambient 1 }
  }
 cylinder { Tan_Point, Tan_Point- 20*z, .05
    pigment { Tan }
    finish { ambient 1 }
  }
  /* something to make the curve show up */
  lathe {
    quadratic_spline
    7,
    Brown_Point,
    Red_Point,
    Orange_Point,
    Yellow_Point,
    Green_Point,
    Blue_Point,
    Tan_Point
    pigment { Blue }
    finish {
      ambient .3
      phong .75
    }
  }

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