// Last edited on 2005-08-28 14:31:42 by stolfi
// Coordinate axes:

#macro arrow(dir,len,rad) 
  union {
    cylinder { <0,0,0>, len*dir, rad }
    cone { len*dir, 3*rad, (len+10*rad)*dir, 0 }
  }
#end

#macro coord_axes(len)
  #local rad = len/300;
  union {
    sphere { <0,0,0>, 2*rad   pigment { color rgb <0,0,0> }}
    object { arrow(x,len,rad) pigment { color rgb <1,0.2,0.2> }}
    object { arrow(y,len,rad) pigment { color rgb <0,1,0> }}
    object { arrow(z,len,rad) pigment { color rgb <0.3,0.3,1> }}
    no_shadow
  }
#end