Newsgroups: comp.graphics, comp.lang.postscript
Path: utzoo!utgpu!watserv1!watnow.waterloo.edu!knewton
From: knewton@watnow.waterloo.edu (K. Glen Newton)
Subject: breaking up polygons with holes, Arc/Info, Maps, cartography
Message-ID: <1991Mar7.203027.21926@watserv1.waterloo.edu>
Sender: daemon@watserv1.waterloo.edu
Organization: University of Waterloo
Date: Thu, 7 Mar 1991 20:30:27 GMT
Lines: 48


hello out there,

	At Energy Mines and Resources Canada we make maps and print
maps. The software used to digitize maps is called Arc/Info. Arc/Info
produces Postscript output. The polygons which make up these maps can
be very large (~4000 vertices). In order to print these maps, a
printing system called Scitex  (no relation to TeX or LaTeX) is used.
Scitex uses another format (it is not important) than Postscript, but
comes with a Postscript-to-Scitex interpreter. Herein lies the problem:
the interpreter cannot handle pathlengths larger that 1500. It dies when
we try to push through our large polygons.

So we thought that we would just break up these polygons. Well, besides
being (very) non-convex, these polygons are not simple (they have holes in
them, and so do the holes - ie. a landmass (polygon) with a lake in
it, with an island in the lake, etc...). Breaking up the polygons is
no longer a simple matter. By the way, Arc/Info codes the holes and
hole-holes by using the sub-path feature of Postscript polygons. This
means that you cannot separate the holes from the polygon very easily,
as you don't want to paint over the hole area, as you cannot exactly
say what is under it.

The chances of getting a "fixed" interpreter are quite low, as it
seems that the Scitex system is used a lot by publishers, but not much
by people making maps (at least not in conjunction with Postscript),
and so are low on the bug/feature fix list.

I'm fairly sure that either someone out there has hit this wall
already, or can help me out in some way. 

Pointers and/or advice will be answered by much thanks, but only code
will guarantee my first born... 


	thanks,

	K. Glen Newton
	software person
	Applied Research & Technology Service
	Energy Mines & Resources Canada (Ottawa)

	knewton@watnow.waterloo.edu
--

............................................................
k. glen newton
knewton@mycologue.waterloo.edu