This is an extrapolation of the now infamous Penrose Triangle illusion 3D model (http://www.thingiverse.com/thing:6513). If you had trouble getting your head around that one, you're not going to find this one any easier! :)Where the triangle used 9 cubes, this arrangement uses 31 cubes to make a larger sorta-notreally-cube.All versions are parallax-corrected for a viewing distance of 40cm. (the larger ones are not simply scaled up versions of the smaller ones)pcube10.stl is the 10cm version, measuring 98.32 x 98.41 x 15.14 mm. pcube15.stl is the 15cm version, measuring 148.03 x 148.15 x 22.03 mm. pcube20.stl is the 20cm version, measuring 197.39 x 196.83 x 28.77 mm.(NEW) pcube15_braced.stl is the 15cm version with some bracing between the blocks to help them stay upright in the first half of the print. (NEW) pcube20_braced.stl is the 20cm version with bracing.The bigger you can print, the better... however as the photos show, even the 10cm version shows the effect very well!No support required.