Path: chuka.playstation.co.uk!news
From: "Jan-Lieuwe Koopmans" <moa@wxs.nl>
Newsgroups: scee.yaroze.programming.2d_graphics
Subject: Re: Rotation problems
Date: Tue, 9 Jun 1998 20:58:58 +0200
Organization: PlayStation Net Yaroze (SCEE)
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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?


I made a tiny program with 180 stars (as GLINE) in the background and a
256x120 translucent sprite, rotating and scaling (screen res. = 512x240) in
PAL mode while drawing translucent filled boxes with a size of 512x240 over
them. I don't have any problems...

(The first part uses 240 smaller translucent, rotating, scaling, brightness
controlled sprites with the 180 GLINE stars in the background... No problems
down there either).

Greets,

Jan-Lieuwe