From e83fa5f24937819c0daeb1c9b9bbaf5de630db87 Mon Sep 17 00:00:00 2001
From: Justin Lin <caterpillar@openhome.cc>
Date: Sun, 18 Aug 2019 10:03:38 +0800
Subject: [PATCH] add packing circles

---
 examples/packing_circles.scad | 64 +++++++++++++++++++++++++++++++++++
 1 file changed, 64 insertions(+)
 create mode 100644 examples/packing_circles.scad

diff --git a/examples/packing_circles.scad b/examples/packing_circles.scad
new file mode 100644
index 00000000..c888e87e
--- /dev/null
+++ b/examples/packing_circles.scad
@@ -0,0 +1,64 @@
+include <util/rand.scad>;
+
+size = [500, 250];
+min_radius = 5;
+max_radius = 50;
+total_circles = 100;
+
+function _packing_circles_out_of_range(size, c) =
+    c[0] + c[2] >= size[0] || 
+    c[0] - c[2] <= 0 ||
+    c[1] + c[2] >= size[1] || 
+    c[1] - c[2] <= 0;
+    
+function _packing_circles_overlapping(circles, c, i = 0) = 
+    i == len(circles) ? false : 
+        let(
+            x = c[0] - circles[i][0],
+            y = c[1] - circles[i][1],
+            a = c[2] + circles[i][2],
+            collision = a >= sqrt(x * x + y * y)
+        )
+        collision || _packing_circles_overlapping(circles, c, i + 1);
+    
+function _packing_circles_packable(size, circles, c) =
+    !_packing_circles_overlapping(circles, c) && 
+    !_packing_circles_out_of_range(size, c);
+
+function _packing_circles_new_min_circle(size, min_radius, attempts, circles, i = 0) = 
+    i == attempts ? [] :
+        let(c = [rand() * size[0], rand() * size[1], min_radius])
+        _packing_circles_packable(size, circles, c) ? c : 
+        _packing_circles_new_min_circle(size, min_radius, attempts, circles, i + 1);
+
+function _packing_circles_increase_radius(size, circles, c, max_radius) = 
+    c[2] == max_radius || !_packing_circles_packable(size, circles, c) ? 
+        [c[0], c[1], c[2] - 1] : 
+        _packing_circles_increase_radius(size, circles, [c[0], c[1], c[2] + 1], max_radius);
+
+
+function _packing_circles_new_circle(size, min_radius, max_radius, attempts, circles) = 
+    let(c = _packing_circles_new_min_circle(size, min_radius, attempts, circles))
+    c == [] ? [] : _packing_circles_increase_radius(size, circles, c, max_radius);
+
+function _packing_circles(size, min_radius, max_radius, total_circles, attempts, circles = [], i = 0) =
+    i == total_circles ? circles :
+    let(c = _packing_circles_new_circle(size, min_radius, max_radius, attempts, circles))
+    c == [] ? _packing_circles(size, min_radius, max_radius, total_circles, attempts, circles) :
+    _packing_circles(size, min_radius, max_radius, total_circles, attempts, concat(circles, [c]), i + 1);
+
+function packing_circles(size, min_radius, max_radius, total_circles, attempts = 100) = 
+    _packing_circles(is_num(size) ? [size, size] : size, min_radius, max_radius, total_circles, attempts);
+    
+circles = packing_circles(size, min_radius, max_radius, total_circles);
+mr = max([for(c = circles) c[2]]);
+translate([0, 0, mr]) for(c = circles) {
+    translate([c[0], c[1]])
+        sphere(c[2], $fn = 48);
+}
+for(c = circles) {
+    translate([c[0], c[1]])
+        linear_extrude(mr) 
+           circle(c[2]/ 3, $fn = 48);
+}
+linear_extrude(1) square(size);