1  use <polyline_join.scad>
 2  use <hollow_out.scad>
 3  use <turtle/t2d.scad>
 4  
 5  radius = 40;
 6  height = 3;
 7  thickness = 1;
 8  width = 1;
 9  
10  min_leng = 0.1;
11  k1 = 0.9;
12  k2 = 0.3;
13  
14  module fern_leaf(t, leng, min_leng, k1, k2, width) {
15      t1 = t2d(t, "forward", leng = leng);
16      polyline_join([t2d(t, "point"), t2d(t1, "point")])
17  	    circle(width / 2);
18      
19      if(leng > min_leng) {
20          fern_leaf(
21              t2d(t1, "turn", angle = 70), 
22              k2 * leng, min_leng, k1, k2, width
23          );
24          
25          t2 = t2d(t1, "forward", leng = k1 * leng);
26          polyline_join([t2d(t1, "point"), t2d(t2, "point")])
27  		    circle(width / 2);
28          
29          t3 = t2d(t2, "turn", angle = -69.0);
30          fern_leaf(
31              t3, 
32              k1 * k2 * leng, min_leng, k1, k2, width
33          );
34          fern_leaf(
35              t2d(t3, "turn", angle = 68.0), 
36              k1 * k1 * leng, min_leng, k1, k2, width
37          );
38      }
39  }
40  
41  module fern_leaf_stencil(radius, height, thickness, width, min_leng, k1, k2) {
42      $fn = 48;
43  
44      linear_extrude(thickness) 
45      difference() {
46          union() {
47              translate([radius, 0])
48              scale([1, 0.5, 1])
49              hollow_out(radius / 3) 
50                  circle(radius / 1.5);
51                  
52              circle(radius);
53          }
54          translate([-radius, 0]) 
55              fern_leaf(
56                  t2d(point = [0, 0], angle = 0), 
57                  radius / 5, min_leng, k1, k2, width
58              );
59      }
60  
61      linear_extrude(height) 
62      hollow_out(thickness) 
63          circle(radius + thickness);
64  }
65  
66  fern_leaf_stencil(radius, height, thickness, width, min_leng, k1, k2);