pointlist:
word	points in list
word	-
dword	x,y,z
...

projectedpointlist:
word	points in list
word	-
.
word	sx
word	sy
word	fl
word	-
dword	z

polygroup:
word sides (0=end)
word color 
word x,y
...

edgelist:
word edges
word -
.
word v1,v2,f,0 	f&8000:hidden edge

hline list:
word starty
...
word x1(-32767=end),x2