add voronoi_holder

examples/voronoi/voronoi_holder.scad

@@ -0,0 +1,42 @@
+use <bend_extrude.scad>;
+use <arc.scad>;
+use <voronoi/vrn2_cells_space.scad>;
+
+size = [200, 72];
+grid_w = 8;        // grid_w must divide size equally.
+thickness = 2;
+spacing = 1.5;
+frags = 24;
+
+module voronoi_holder() {
+    half_spacing = spacing / 2;
+    cells = vrn2_cells_space(
+        size = size,
+        grid_w = grid_w
+    );
+
+    r = size[0] / (2 * PI) - thickness * 1.5;
+          
+    difference() {
+        bend_extrude(size = size, thickness = thickness * 3, angle = 360, frags = frags) 
+        render() 
+        difference() {
+            square(size);
+            render() 
+                for(cell = cells) {
+                    offset(-half_spacing)
+                    polygon(cell[1]);
+                }
+        }
+        linear_extrude(size[1] - thickness)
+           arc(radius = r, angle = 360, width = thickness, $fn = frags);
+    }
+
+    linear_extrude(thickness)
+        circle(r + thickness * 1.75, $fn = frags);
+
+    linear_extrude(thickness * 2)
+        circle(r - 0.25 * thickness, $fn = frags);        
+}
+
+voronoi_holder();