missing in the article, but you can actually make 3D versions of this playing with perspective, although it will only work from a very specific viewing angle.

missing in the article, but you can actually make 3D versions of this playing with perspective, although it will only work from a very specific viewing angle. See, for example the 3D printed penrose triangles on thingiverse https://www.thingiverse.com/thing:6513 https://www.thingiverse.com/thing:6513