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From: shn@allgfx.agi.oz (Si-Hanh NGUYEN)
Newsgroups: comp.graphics
Subject: How does pr_vector() work ?
Message-ID: <1990Feb25.222157.26389@allgfx.agi.oz>
Date: 25 Feb 90 22:21:57 GMT
Organization: All Graphic R+D
Lines: 20


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