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Povray is a raytracing program and programming language. Advantages of Povray over other commercial raytracers: the software is open source, syntax is pretty much frozen, the files are small and intelligable ASCII files. The picture to the left had been generated with the code below. Povray is installed on Abel.
// oliver knill, 2005, harvard math department povray demo

camera      { location <0,3,-5> right x up y look_at <0,0,0>}
light_source{ <0,3,-5> color rgb <1,1,1> }
background  { rgb <1,1,1> }

#macro Hyperboloid(c,d)
  quadric {<1,-1,1>,<0,0,0>,<0,0,0>,c 
    hollow clipped_by { sphere{<0,0,0> d} }

#declare i=-1;
#while (i<2)
union {
   object{ Hyperboloid(-i/2,2.1-i/2)
     texture {
       pigment { rgb <1,1/2+i/2,0> }
       finish  {phong 0.5 ambient 0.5 diffuse 1.0}
#declare i=i+1;

Simplicity, Clarity, Generality B.W. Kernighan, R. Pike, in "The Practice of Programming".