Added chamfer_hole() utility module.

utils/chamfer.scad

@@ -0,0 +1,38 @@
+//
+// NopSCADlib Copyright Chris Palmer 2024
+// 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/>.
+//
+
+//
+//! 45 degree chamfer the entrance to holes.
+//!
+//! If the hole shape is concave then it must be described as a list of 2D convex children.
+//
+include <core/core.scad>
+
+module chamfer_hole(depth = 1) {    //! Chamfer a hole given a 2D outline as a child
+    for(i = [0 : $children - 1])
+        hull() {
+            linear_extrude(eps)
+                offset(depth)
+                    children(i);
+
+            translate_z(-depth)
+                linear_extrude(eps)
+                    children(i);
+        }
+}