FreeLists / openbeos / [openbeos] Re: The Scientific Method aka Bresenham NewsletterArticle

["Alexander G. M. Smith" <agmsmith@xxxxxxxxxx>]

Michael Phipps wrote on Mon, 09 Jun 2003 19:01:31 -0400:
> I didn't consider this. Given the 80 bit nature of the FPU and the (fairly) 
> small numbers that we are using, it wouldn't seem like it could ever be a 
> more than 1 pixel error. I did see differences between the two algorithms, 
> but I really had/have no real way to prove error.

That sort of rounding problem shows up as gaps between polygons in 3D systems, 
since the edges are usually placed using a line drawing algorithm.  You want 
the line to be exactly the same, no matter what the order of the endpoints is.  
It's a bit trickier since the vertices are floating point numbers until the 
very last transformation step.  Takes a lot of care to get it "pixel perfect".

- Alex