// Last edited on 2011-05-08 09:38:26 by stolfi
// COORDINATE AXES

#macro coord_axis(tip,rad,cor,tag)
  // Coordinate axis from origin to {tip}, with
  // stem radius {rad}, color {cor}, and name {tag} (unused).
  #local L_full = vlength(tip);
  #local L_head = 20*rad;
  #local b_head = ((L_full - L_head)/L_full)*tip;
  union{
    sphere{ <0,0,0>, rad }
    cylinder{ <0,0,0>, 1.01*b_head, rad }
    cone{ b_head, 3*rad, tip, 0.00 }
    texture{ pigment{ color rgb cor } finish{ ambient 0.5 diffuse 0.5 } }
  }
#end

#macro coord_axes(L)
  // The three coordinate axes, each with length {L}
  // Axis X is red, Y is green, Z is blue.
  #local rad = 0.0040*L;
  union{ 
    object{ coord_axis( <L,0,0>, rad, <1.0,0.2,0.2>, "X") }
    object{ coord_axis( <0,L,0>, rad, <0.0,0.8,0.0>, "Y") }
    object{ coord_axis( <0,0,L>, rad, <0.3,0.3,1.0>, "Z") }
  }
#end