From:	"Chris Wise" <wise AT eng2 DOT eng DOT monash DOT edu DOT au>
Newsgroups:	comp.os.msdos.djgpp
Subject:	Re: Help with bit-masking Allegro sprites
Date:	18 Jul 1997 08:26:47 GMT
Organization:	Materials Engineering, Monash
Lines:	27
Message-ID:	<01bc9354$55010f40$cf86c282@mat-wise.eng.monash.edu.au>
References:	<869142033 DOT 25228 DOT 0 DOT nnrp-5 DOT 9e9829a4 AT news DOT demon DOT co DOT uk>
NNTP-Posting-Host:	mat-wise.eng.monash.edu.au
To:	djgpp AT delorie DOT com
DJ-Gateway:	from newsgroup comp.os.msdos.djgpp

BDC Client Team <cs19 AT cityscape DOT co DOT uk> wrote in article
<869142033 DOT 25228 DOT 0 DOT nnrp-5 DOT 9e9829a4 AT news DOT demon DOT co DOT uk>...
> Hi all,
> 
> I have been working on a routine for a pixel-perfect collision detection
> for Allegro sprites.  The basic idea is that you create a bit-mask
> for each Allegro sprite, do general bounding-box detection until
> this flags a collision and then use the bit-masks to see if a *true* 
> collision has occured (i.e. actual pixels overlap).
> 
> I'm fairly sure that I am creating the bit-masks correctly, but when I
come
> to (logically) 'and' two bit-masks together I get false returns all the
time.
> I have gone through my code time and again, and just can't spot where I
> am going wrong.

I suggest that you take a look at this article. 
http://www.ddj.com/ddsbk/1995/1995.05/roberts.htm
I found it very helpful.

> Would anyone out there be prepare to look at the code (it's only 300
lines long)
> and point me in the right direction?

Send it to me and I'll have a look. Can't promise anything though.
Chris Wise

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