acorn/Paraboloid.scad

   1 //////////////////////////////////////////////////////////////////////////////////////////////
   2 // Paraboloid module for OpenScad
   3 //
   4 // Copyright (C) 2013  Lochner, Juergen
   5 // http://www.thingiverse.com/Ablapo/designs
   6 //
   7 // This program is free software. It is
   8 // licensed under the Attribution - Creative Commons license.
   9 // http://creativecommons.org/licenses/by/3.0/
  10 //////////////////////////////////////////////////////////////////////////////////////////////
  11
  12 module paraboloid (y=10, f=5, rfa=0, fc=1, detail=44, x, hi){
  13         // y = height of paraboloid
  14         // f = focus distance
  15         // fc : 1 = center paraboloid in focus point(x=0, y=f); 0 = center paraboloid on top (x=0, y=0)
  16         // rfa = radius of the focus area : 0 = point focus
  17         // detail = $fn of cone
  18
  19         hi = (y+2*f)/sqrt(2);                                                           // height and radius of the cone -> alpha = 45° -> sin(45°)=1/sqrt(2)
  20         x =2*f*sqrt(y/f);                                                                       // x  = half size of parabola
  21
  22    translate([0,0,-f*fc])                                                               // center on focus
  23         rotate_extrude(convexity = 10,$fn=detail )              // extrude paraboild
  24         translate([rfa,0,0])                                                            // translate for fokus area
  25         difference(){
  26                 union(){                                                                                        // adding square for focal area
  27                         projection(cut = true)                                                                                                                                                  // reduce from 3D cone to 2D parabola
  28                                 translate([0,0,f*2]) rotate([45,0,0])                                                                                                   // rotate cone 45° and translate for cutting
  29                                 translate([0,0,-hi/2])cylinder(h= hi, r1=hi, r2=0, center=true, $fn=detail);    // center cone on tip
  30                         translate([-(rfa+x ),0]) square ([rfa+x , y ]);                                                                                 // focal area square
  31                 }
  32                 translate([-(2*rfa+x ), -1/2]) square ([rfa+x ,y +1] );                                         // cut of half at rotation center
  33         }
  34 }
  35
  36
  37 //paraboloid (y=50,f=10,rfa= 0,fc=1,detail=120);
  38 paraboloid (y=50,f=10,rfa= 0,fc=1,detail=120);