explains the situation — 3D modeller Ulrich Schwanitz, known as user on 3D modelling forum Shapeways, created a 3D printout based on the ‘impossible triangle’ optical illusion. After a video of the shape was released, worked out how to create the shape and uploaded instructions to the Thingiverse Web site, another repository of 3D models and content.

Schwanitz sent the Thingiverse Web site operators a DMCA takedown notice asserting copyright over the design, but later withdrew the complaint after deciding to release his design into the public domain. The Penrose Triangle illusion exists in the public domain and can be modified or reproduced without any copyright infringement, but Schwanitz’s initial claims suggested he wished to maintain copyright over his 3D interpretation. Schwanitz moderated his position when it was established similar or near-identical creations could be made based on the original Penrose Triangle illusion, without infringing his copyright.

Several derivative designs have since been created based on the Penrose Triangle design, including by Sydney-based 3D modeller — who has created both of Schwanitz’s original triangle model, and what he calls a .

Concerns over copyright and 3D printers has , with enterprising users theoretically able to reproduce patented designs through reverse engineering and intensive modelling work.