How does pr_vector() work ?

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Article #14067

#14067

From: Si-Hanh NGUYEN
Date: Sun, 25 Feb 1990 22:11

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Does anybody know the detailed algorithm used in pr_vector() of Sun
Pixrect ?  The manual says that "pr_vector draws balanced vectors. (The
technique used is to balance the Breshenham error term)".

I have to fill some shapes which have straight edge(s) by pr_traprop(),
and I would like these edges align perfectly with lines drawn by
pr_vector() (or bold lines by pr_polygon_2()). I need to know how
pr_vector() works in order to derive the bit vector of chain of those
straight edges. 

I have tried the Bresenham algorithm from Foley an Van Dam. It works
except when the line segment is in the 4th and 8th octant (Y-axis is from
top to bottom and slope of the line segment is in ]0,-1[).

Any help would be greatly appreciated.

Si-Hanh Nguyen
shn@allgfx.agi.oz

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Path: arc1-ca.pugleaf.net!utzoo!utgpu!watserv1!watmath!iuvax!mailrus!cs.utexas.edu!rice!sun-spots-request
From: shn@allgfx.oz.au (Si-Hanh NGUYEN)
Newsgroups: comp.sys.sun
Subject: How does pr_vector() work ?
Keywords: Windows
Message-ID: <5461@brazos.Rice.edu>
Date: 25 Feb 90 22:11:38 GMT
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