Path: chuka.playstation.co.uk!news
From: yaroze@theburrow.co.uk (Barry & Robert Swan)
Newsgroups: scee.yaroze.beginners
Subject: Re: Collision Detection!.....(Joy)
Date: Thu, 24 Jun 1999 22:59:45 GMT
Organization: PlayStation Net Yaroze (SCEE)
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well, my two example bits of code were a bit unrelated (blushes).

the first part was just for creating a 1bit mask (It should really be
called 1 bit all along). and would take the scrolling of the sprite
into account already (i think, cant remember and too lazy to check!)

The second was slightly different; iamge you had 2 16x16 masks for
each sprite when aligned to an x multiple of 8. The routine would take
in any x and y for each of these two sprites and compare that; ie if
you have 200 bullet sprites, you wouldnt need to create a mask for
each one, just have one pixel aligned version and then use that mask
by bitshifting to replicate the sprites true x position (which may be
8pixel aligned or not).

Does that make sense?

I wasnt really clear about the whole thing to be honest!

Sos, 
Rob

>Surely you do not need to use any shifts to detect the results of anding the
>two images? I would have thought it would be quicker to check the ints or
>longs for TRUE as any value other than zero is true. Going back to the
>original idea of the array containing a 2 bit area of the screen size with
>the two 2 bit masks anded on as per instructions ;) The following function
>will check it far quicker than using shifts. Oh, this routine assumes the
>screen res is 320x256 :)