"Rafal 'Raf256' Maj" <raf### [at] raf256com> wrote in 
news:Xns### [at] 204213191226:

> I wanted to use sphere_sweep to generate a scalled torus, like 
>   torus { 10,5 scale <4,1,1> 
> *but* I wanted it's section to be a circle (and not to get deformed) 
> - so I wanted an cylinder wrapped into elipse shape.
> 
> But usig sphere sweep didnt help:
>   http://www.raf256.com/3d/torus_as_spline.jpg
> 
> as we see in "yellow" segment - section is deformed.
> 
> is this a bug or a is this expected behaviour of sphere_sweep?
> 
> Sweep is build from points spaced equaly along scalled torus shape:
> 
>   sphere_sweep {
>     linear_spline  //cubic_spline 
>     #local E=45/4; // precission
>     (360/E)+3
>     #local I=-E; #while (I<=360+E)
>       vrotate(<0,0,Major>, <0,I,0>)*Scale, Minor
>     #local I=I+E; #end
>   }


Try this Rafal:

#declare Major = 5.0;
#declare Minor = 1.5;
#declare Scale = <3.0, 1.0, 0.5>;

difference {
  union {
    #declare I = 0;
    #while (I < 360)
      sphere { Scale*vrotate(Major*z, I*y), Minor }
      #declare I = I + 1;
    #end // while  
    pigment { color rgb <1, 1, 1> }
  }
  plane { z, 0 pigment { color rgb <1, 1, 0> } }
}

camera { location -30*z look_at 0*y }
light_source { <1, 4, -4>*100 color rgb <1, 1, 1> shadowless }
background { color rgb <0.5, 0.5, 1> }


Tor Olav

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