Path: chuka.playstation.co.uk!scea!greg_labrec@interactive.sony.com
From: jamin1@psu.edu (Jamin Frederick)
Newsgroups: scea.yaroze.programming.2d_graphics
Subject: pixels
Date: Mon, 07 Jul 1997 17:13:32 GMT
Organization: SCEA Net Yaroze News
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Hi, how's it going?  I'm working on my pixel-by-pixel collision
detection algorithm, and I've run into a problem of actually trying to
access pixel data of sprites.  It seems like I won't be able to access
the data the lies in the video memory once it has been transferred
from the main memory, since there are no api calls to do this, plus,
trying to access this memory probably interferes with the video
syncing and drawing mechanism.  The only thing left to do is use the
pixel data that's been in main memory from the loaded TIM.
The only thing is, that this memory could be otherwise used for
something else.

So I have pixel data both in the video memory AND in main memory,
which is sort of redundant, but main memory is the only way to go.

My question is, is there any way to replace data that's already been
loaded from siocons?  For example, if I loaded my TIM at 0x80090000,
and then during program execution, I transfer this from main memory to
video memory, so that I no longer need what's at 0x80090000, is there
any easy way to reload data back into this position for use?

The reason I want this to be answered is that I guess I'm planning to
make my pixel-by-pixel algorithm based on pixel data in main memory,
and I don't want it to be a silly approach.  I mean, if someone
actually does want to reclaim use of that main memory, that is, then
the algorithm will totally fail!  

In general, is it a waste of space to have all your image data sitting
in main memory?  Is there any way your program heap can plow past some
of this  data, once it's been utilized?  Or perhaps have a spot just
for incoming data and use I/O to reload into that spot during program
execution...which only CodeWarrior people can do at this point?

Thanks, 

Jamin
jamin1@psu.edu