Added source code

utils/round.scad

@@ -0,0 +1,44 @@
+//
+// NopSCADlib Copyright Chris Palmer 2018
+// nop.head@gmail.com
+// hydraraptor.blogspot.com
+//
+// This file is part of NopSCADlib.
+//
+// NopSCADlib is free software: you can redistribute it and/or modify it under the terms of the
+// GNU General Public License as published by the Free Software Foundation, either version 3 of
+// the License, or (at your option) any later version.
+//
+// NopSCADlib is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY;
+// without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+// See the GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License along with NopSCADlib.
+// If not, see <https://www.gnu.org/licenses/>.
+//
+
+//! Round 2D shapes uisng `offset()`, which is fast and 3D shapes with [`offset_3D()`](#offset), which is very slow.
+//!
+//! A single radius can be specified or separate internal and external radii.
+//! If `chamfer_base` is `true` for `round_3D()` then the bottom edge is made suitable for 3D printing by chamfering once the
+//! the angle gets shallower than 45 degrees.
+include <../core.scad>
+use <offset.scad>
+
+module round(r, ir = undef, or = undef) { //! Round a 2D child, single radius or separate inside and outside radii
+    IR = is_undef(ir) ? r : ir;
+    OR = is_undef(or) ? r : or;
+    offset(OR)
+        offset(-OR -IR)
+            offset(IR)
+                children();
+}
+
+module round_3D(r, ir = undef, or = undef, chamfer_base = false) { //! Round a 3D child single radius or separate inside and outside radii
+    IR = is_undef(ir) ? r : ir;
+    OR = is_undef(or) ? r : or;
+    offset_3D(OR, chamfer_base)
+        offset_3D(-OR -IR, chamfer_base)
+            offset_3D(IR, chamfer_base)
+                children();
+}