Doctor John schreef:
> Thought I'd share this with you all.
> IMNSHO it's the best rendering of (part of) the Barth Decic that I've seen 
> for a while.
> 
> For the record:
> #declare a=1.0
> #declare GM=(sqr(5)+1)/2
> #declare GM4=pow(GM, 4)
> 
> function(x,y,z,a) {
>  8*(pow(x, 2)-GM4*pow(y, 2))*(pow(y, 2)-GM4*pow(z, 2))*(pow(z, 2)-
>  GM4*pow(x, 2))*(pow(x, 4)+pow(y, 4)+pow(z, 4)-2*pow(x, 2)*
>  pow(y, 2)-2*pow(x, 2)*pow(z, 2)-2*pow(y, 2)*pow(z, 2))+(3+5*GM)
>  *pow((pow(x, 2)+pow(y, 2)+pow(z, 2)-pow(a, 2)),2)*pow((pow(x, 2)
>  +pow(y, 2)+pow(z, 2)-(2-GM)*pow(a, 2)),2)*pow(a, 2)
> }
> 
> max_gradient 25060
> contained_by{sphere {0, 1.9}}
> 
> 
> ...and the texture:
> texture {
>  pigment {
>   aoi <3, 1, 3>
>   color_map {
>    [0 color rgb <1.0,0.4,0.25>]
>    [0.8 color rgb <0.15,0.25,0.9>]
>   }
>  }
>  finish {
>   ambient 0
>   diffuse 0.7
>   specular 0.16
>  }
> }
> 
> Must be rendered using Megapov >=1.1
> 
> John
Barth's SEXTIC is a surface with 65 double points. It's interesting to 
know that 20 of these double points are the vertices of a regular 
dodecahedron and 30 other double points are the midpoints of the edges 
of another regular dodecahedron. Both dodecahedra have the same center 
and the edges are parallel. I have illustrated this property in a small 
animated gif.
I used the "poly" representation of the surface and not "function".
More images can be seen here:
http://cage.ugent.be/~hs

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