fix a_step == 0

src/experimental/arc_great_circle.scad

@@ -6,7 +6,38 @@ function arc_great_circle(p1, p2, center = [0, 0, 0]) =
         radius = norm(p1 - center),
         normal_vt = cross(p2, p1),
         a = acos(p2 * p1 / pow(radius, 2)),
-        steps = round(a / (360 / __frags(radius))),
-        a_step = a / steps
+        steps = round(a / (360 / __frags(radius)))
     )
-    [for(i = [0:steps]) ptf_rotate(p1, a_step * i, normal_vt)];
+    steps == 0 ? [p1, p2] :
+    let(a_step = a / steps)
+    [for(i = [0:steps]) ptf_rotate(p1, a_step * i, normal_vt)];
+
+/*
+use <experimental/arc_great_circle.scad>
+use <voronoi/vrn_sphere.scad>
+use <fibonacci_lattice.scad>
+use <polyline_join.scad>
+
+n = 10;
+radius = 10;
+
+points = fibonacci_lattice(n, radius);
+#for(p = points) {
+    translate(p)
+        sphere(.5);
+}
+
+%sphere(radius);
+
+for(cell = vrn_sphere(points)) {
+    pts = concat(cell, [cell[0]]);
+
+    for(i = [0:len(pts) - 2]) {
+        p1 = pts[i];
+        p2 = pts[i + 1];
+        arc = arc_great_circle(pts[i], pts[i + 1], $fn = 36);
+        polyline_join(arc)
+            sphere(.5, $fn = 4);
+    }
+}
+*/