Path: chuka.playstation.co.uk!news
From: "Martin Swaine" <martin@lightwork.co.uk>
Newsgroups: scee.yaroze.programming.2d_graphics
Subject: Re: Animating sprites
Date: 15 May 1998 18:48:41 GMT
Organization: Lightwork Design
Lines: 45
Message-ID: <01bd803a$2c971800$80c809c0@antonio.lightwork>
References: <01bd7ac4$e4eda480$7397989e@antonio.lightwork>
NNTP-Posting-Host: lightwk.demon.co.uk
X-Newsreader: Microsoft Internet News 4.70.1162

Thanks people for your comments. I now have better information.

This effect can be replicated with the Sony's Check program (the one where
all the balls bounce around the screen) that comes with the Yaroze kit.

If you change the source so the deltas for x and y are quite large (say 10
or 20) you see the effect I mean when you keep the number of balls at one.
The illusion of the "trail" of balls is clearly visable. I guess this means
I am using the drawing primitives and double buffering correctly.

In response to the other questions, my sprite has semi-transparency off and
is of a single colour (red). However, since this problem is reproducable
with the Sony demo code then I believe there can be no unique problem with
my code.

I too was drawn to Robert's suggestion that it maybe a deception of the
eye, but am a little suprised as I have never seen this manifest with TV or
video images before.

Martin Swaine <martin@lightwork.co.uk> wrote in article
<01bd7ac4$e4eda480$7397989e@antonio.lightwork>...
> Hi,
> 
> Can anyone help please?
> 
> I am developing a demo in which a sprite is moved along a spline curve.
The
> co-ordinates are precalculated so the program only needs to keep
redrawing
> the sprite at these positions.
> 
> To keep the thing fast the distance between each consecutive instance of
> the sprite is quite large. The problem is I am seeing a trail of several
> dimmer copies behind the current sprite. 
> 
> I have reduced the brightness of the object in case the screen phospher
was
> not decaying fast enough. I am using the standard sequence of
> Vsync/Drawsync and other drawing primitives.
> 
> Has anyone else ever seen this? What might I be doing wrong?
> 
> Thanks,
> Martin
>