The shadow of this cube in different directions gives QR codes pointing to the Wikipedia articles for Kurt Godel, M.C. Escher, and J.S. Bach respectively. Also a pretty challenging print test. Note that QR codes cannot be read in mirror image, so only 3 of the 6 possible cube orientations cast a readable shadow.
Notes. This was generated using a reduced-url QR code generator, a paint program to connect disconnected sections, Inkscape to convert to dxf, and OpenScad to extrude, rotate, and intersect the 3 images. OpenScad rendering took almost 30 minutes on a fast computer.
QR codes are fortunately very forgiving of fairly large modifications due to their built-in parity and redundancy schemes, and I verified readability of the images up through the dxf stage. (Although I got pretty close to the limit on one image, and my camera QR scanner had to rescan a few times to get a read.)
This is a complex image. To get a readable shadow your light source will need to be pretty far away to get a flat pass through. Perhaps someday I’ll do a version with transformed geometry, matching specific close-up point sources.
If you can’t get it to print cleanly enough to read, hey, claim it’s a Borg Cube and gift it to your Trekkie friends.
Stop breadboarding and soldering – start making immediately! Adafruit’s Circuit Playground is jam-packed with LEDs, sensors, buttons, alligator clip pads and more. Build projects with Circuit Playground in a few minutes with the drag-and-drop MakeCode programming site, learn computer science using the CS Discoveries class on code.org, jump into CircuitPython to learn Python and hardware together, or even use Arduino IDE. Circuit Playground Express is the newest and best Circuit Playground board, with support for MakeCode, CircuitPython, and Arduino. It has a powerful processor, 10 NeoPixels, mini speaker, InfraRed receive and transmit, two buttons, a switch, 14 alligator clip pads, and lots of sensors: capacitive touch, IR proximity, temperature, light, motion and sound. A whole wide world of electronics and coding is waiting for you, and it fits in the palm of your hand.