I created this illusion by placing a chair in the middle of the room and shining a bright light on it which created a shadow. I cut black poster board and taped it so that it covered the shadow. Then I moved the light source to the opposite side of the room and shined it on the chair which created another shadow. Again, I cut black poster board and taped it so that it covered the shadow. Then I just removed the actual chair from inbetween the 2 shadows. The whole process took about 10 hours.