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From: teittinen@cc.helsinki.fi
Newsgroups: comp.os.msdos.programmer
Subject: Need a good line drawing function for VGA
Message-ID: <1991Mar14.020823.5530@cc.helsinki.fi>
Date: 14 Mar 91 02:08:23 GMT
Organization: University of Helsinki
Lines: 29

Hello!

I'm writing a program that draws red-blue stereopictures on the screen
and I have a problem. Now I probably should tell you that I'm writing
this program in TC++. Anyway, because I draw two pictures of the object
in different colors, I don't want either color to wipe the other out. So
I use XOR-mode for drawing the lines (setwritemode(1);). But now the
problem is that when two lines in one image overlap, the overlapping
part is erased. And this is not too rare, for I draw wire-frame images
of the objects.

So what I need is possibility to draw lines using OR-mode. But here I'm
unlucky, Borland doesn't give me chance to use OR-mode for drawing lines
(even though my VGA hardware can make it easily). I could implement this
feature myself, but when I implemented line drawing algorithm in C and
compiled it, it was 3 times slower than Borland library function (I
timed it with Profiler). And because I'm trying to do some animation
here, I'd need as fast routine as I can get.

I'm turning to you, my fellow programmers, and asking if anyone has
an assembler version of a suitable VGA line drawing function that he/she
could share with me. I'd be very grateful to get this function. Or is
there a suitable function in (gasp) Microsoft C, must I turn to them ?
Please, don't say so! I'll do (almost) anything but that :-)

-- 
E-Mail: teittinen@finuh.bitnet               ! "Studying is the only way
        teittinen@cc.helsinki.fi             !  to do nothing without
Marko Teittinen, student of computer science !  anyone blaming you" -me