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From: achim@forst.informatik.rwth-aachen.de (Achim Schmidt)
Newsgroups: comp.sys.amiga.programmer
Subject: Questions about the BLITTER
Keywords: Amiga,Blitter,Line drawing
Message-ID: <achim.677426600@forst>
Date: 20 Jun 91 14:03:20 GMT
Sender: news@rwthinf.UUCP
Distribution: comp
Lines: 21

I've written a routine which does line drawing with the blitter. 
But I found out, that there are some mistakes ... I wonder, if its
my code or the blitter ?

1. The lines are normally a few pixels to the left or right from the
 endpoint. That depends on the line, if its going to the right or to the 
 left. 
 Am I using the wrong algorithm to calculate the blitter-reg values or 
 is it a calculation error in the Blitter ?

2. When (x2-x1) > 2* (y2-y1) then the point in the last line (=y2) is missing.
  That has some strange effects, when filling a polygon...
  I fixed it by simply adding 1 to the Blitterline length register.
  Is that correct ?

3. How does Move()/Draw() work ??  Do they use the blitter?

Thanks for your help...

 
achim@forst.informatik.rwth-aachen.de