About this 3D model

Lithophanes have been around for years (before 3d printers) but I never knew it till I watched this video by RCLifeOn. https://www.youtube.com/watch?v=y63sVpeViXo I thought it look cool so I tried 3D printing one. This one had thin spots with holes so I'm going to try printing more. Hold this up to some light and an image will appear.