// Arrows
// Last edited on 2012-09-29 06:16:15 by stolfilocal

#macro arrow(va,ra)
  // An arrow from origin.
  // {va} Coords of tip of arrow.
  // {ra} Radius of shaft.
  #local da = vlength(va);  // Total length of arrow.
  #local dh = 16.0*ra;       // Length of arrowhead.
  #if (da > 0.001*ra)

    #local vs = va*(da - 0.95*dh)/da; // Coords of end of shaft.
    #local vh = va*(da - dh)/da;      // Coords of base of head.
    #local rh = 4*ra;                 // Radius of base of head.
    difference{
      union{
        cylinder{ <0,0,0>, vs, ra }
        cone{ vh,rh, va,0 }
      }
      plane{ va,0 }
    }
  #end
#end