v -30 0 -30 v 30 0 -30 v 30 0 30 v -30 0 30 v 0 60 0 c 0 0 0 l 0 1 l 0 3 l 0 4 l 1 2 l 1 4 l 2 3 l 2 4 l 3 4 color 0 255 0 #1th number indicate how may lines in the face #line index starting from 1. If it is negative, it means reverse the staring # and ending point of line f 3 -1 3 -5 f 3 5 -7 -4 f 3 7 -8 -6 f 3 8 -3 2 f 4 1 4 6 -2