Mojoptix used OpenSCAD to design a gnomon with many tiny holes. I don’t understand how he calculated the holes’ arrangement, but I do know the end result. When set up properly, the sundial will redirect light to display the correct time on the surface below it. The sundial displays the time from 10:00 to 16:00 in 20 minute increments.
You can skip to 13:04 in Mojoptix’s video to see it in action, but the whole thing is enlightening:
Mojoptix believes that the holes on his gnomon are so tiny that you can make it only through 3D printing. Neat huh? Head to Mojoptix’s Thingiverse page to download the gnomon’s 3D files. You can also buy a ready-to-assemble sundial kit from his Etsy store for ~$55 (USD).