Add example for rotate_extrude().

examples/Basics/rotate_extrude.scad

@@ -0,0 +1,35 @@
+echo(version=version());
+
+// rotate_extrude() always rotates the 2D shape 360 degrees
+// around the Z axis. Note that the 2D shape must be either
+// completely on the positive or negative side of the X axis.
+color("red")
+    rotate_extrude()
+        translate([10, 0])
+            square(5);
+
+// rotate_extrude() uses the global $fn/$fa/$fs settings, but
+// it's possible to give a different value as parameter.
+color("cyan")
+    translate([40, 0, 0])
+        rotate_extrude($fn = 80)
+            text("  J");
+
+// Using a shape that touches the X axis is allowed and produces
+// 3D objects that don't have a hole in the center.
+color("green")
+    translate([0, 30, 0])
+        rotate_extrude($fn = 80)
+            polygon( points=[[0,0],[8,4],[4,8],[4,12],[12,16],[0,20]] );
+
+
+// Written in 2015 by Torsten Paul <Torsten.Paul@gmx.de>
+//
+// To the extent possible under law, the author(s) have dedicated all
+// copyright and related and neighboring rights to this software to the
+// public domain worldwide. This software is distributed without any
+// warranty.
+//
+// You should have received a copy of the CC0 Public Domain
+// Dedication along with this software.
+// If not, see <http://creativecommons.org/publicdomain/zero/1.0/>.