Path: chuka.playstation.co.uk!news
From: shrewrs@aol.com (Robert Swan)
Newsgroups: scee.yaroze.programming.2d_graphics
Subject: Rotation problems
Date: Fri, 06 Mar 1998 22:50:27 GMT
Organization: PlayStation Net Yaroze (SCEE)
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Message-ID: <35007aa1.25789418@news.playstation.co.uk>
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I've been using rotation on sprites extensively in my game, but have
come up with the following problems that REALLY annoy me. Is there
something obvious I am doing wrong, or is it (as I assume) yet another
bug in the psx (I was going to put 'another' in caps, but thought two
capitalised words would merely annoy)

I have a sprite of size 256 by 256. (8 bit). It is perfectly within a
texture page. I put it on screen, with about 5 others, and the
computer slows right down; ridiculously so. Considering the processor
can handle several hundred 32 by 32 sprites per frame, a couple of
256x256 should be no problem. But it gets worse. I really wanted to
have these sprites zoomed by a factor of 2 and rotating. What happens
is that the sprites flicker on and off at random, and slow down the
game even further. I tried a workaround of using a 128x128 sprite and
zooming it by four, but to no avail. here are some strange results
I've found -

256x256 sprite - very slow
256x256 sprite with rotation and/or scaling above x1 - not only very
slow, but flickers on and off
128x128 sprite with scaling x2 works
128x128 sprite with scaling above x2 and/or rotation flickers and
slows down
smaller sprites than 128x128 when scaled above x3-4 with rotation it
appears that certain angle values are ignored. Eg, when at angles
1024, 2048 etc it draws it as though at angle 0

These problems are wierd and annoying. It now means instead of having
a lovely huge 256x256 sprite scaled to be over a screen in height I
now have to settle for a measly 128x128 sprite that looks tiny
(especially since I switched my game to hi res mode)

I've got enough packet workspace... any suggestions before I smash up
my university's property?

Robert Swan
rs108@mdx.ac.uk
http://www.netyaroze-europe.com/~middex2