This is a heavily cleaned & modified version of artur83's Penrose Triangle, which was a great design however not printable.It is now enlarged (longest dimension 99.97mm) and printable on almost any FDM printer without requiring support. Walls have been thickened at the bottom to ensure a secure footing and to minimise excess overhang angles.Best viewed with one eye closed - looking at it with 2 eyes almost ruins the illusion :)NB: A new improved version has been released! http://www.thingiverse.com/thing:6513Simply print, support not required!(the one in the photo was printed on a Rapman 3.1 with Orbi-PLA, but it is designed to be printable on a Makerbot or Mendel or any other printer really)