Path: chuka.playstation.co.uk!news
From: "Martin Swaine" <martin@lightwork.co.uk>
Newsgroups: scee.yaroze.programming.2d_graphics
Subject: Re: Animating sprites
Date: 20 May 1998 10:09:33 GMT
Organization: Lightwork Design
Lines: 105
Message-ID: <01bd83df$772808e0$80c809c0@antonio.lightwork>
References: <01bd7ac4$e4eda480$7397989e@antonio.lightwork> <01bd803a$2c971800$80c809c0@antonio.lightwork> <355E0F4F.1CFAECA7@ndirect.co.uk>
NNTP-Posting-Host: lightwk.demon.co.uk
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Thanks Alex for your explanation. I am however still unsure if I can do
anything practical to avoid this problem. It seems a shame to abandon this
work because of a disapointing display.

If you are interested, I have uploaded the source etc. to

http://www.netyaroze-europe.com/~mtn446/ftp/spline.zip

Can anyone suggest code changes that might avoid the ghosting.

Alex Herbert <aherbert@ndirect.co.uk> wrote in article
<355E0F4F.1CFAECA7@ndirect.co.uk>...
> 
> 
> Martin Swaine wrote:
> 
> > 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.
> 
> Oh right, I see.  Sorry, I did know about this effect, but from your
arriginal
> description I thought it was something more complcated.  Robert's
suggestion is
> true to a degree.  But if you are running at the full fame rate (i.e. 50
or
> 60fps) then this effect it not mormally noticable.  Drop your frame rate
to
> 25fps and the "movement ghosting" becomes very obvious.  Try a fast full
screen
> scroll at 50fps, then at 25fps.  At 50fps it look silky smooth, but at
25fps it
> ugly as hell.  It is also more noticable if there is a high contrast
between
> the object which is moving, and the surface it is moving over.
> 
> However, this effect is less noticable in most 3D environments.  This is
> because 'realistc' 3D worlds tend to be built up with mid-tones and
colours
> with less saturation.  And, the relative screen movements tend to be
smaller
> and less consistent.  In this way, the ghosts get lost (to some degree) 
in the
> overall picture, and you can get away with a slower frame rate.  Arcade
machine
> manufacturers such as Namco and Sega, usually design their software to
run at
> the full 60fps to get that perfect smoothness.  Compare Ridge Racer on
the PSX
> and in the arcade, and weep at the difference!
> 
> With regard to TV and video...
> 
> Game video has an effective camera exposure time of 0, and you are
creating
> movement from static images.  In the real world, video and film cameras
have a
> longer exposure time and catch movement within one frame.  (Pause your
VCR at a
> point where there is fast movement on the screen to see what I mean.) 
This
> "motion blur" hides the ghosting effect (by not having any hard edges
> perpendicular to the direction of movement).  Conversly, if you are
watching a
> cartoon (which is made up of static images) you can see the ghosting.  It
is
> especially noticable when the camera is panning over a background.
> 
> Interestingly, motion blurring can be created in software realtime, but
it
> takes a hell of a lot of processing power to get it right.  This is
something I
> expect to see done in hardware in the next generation of games machine.
> 
> Anyway, I gone on far too long already...
> 
> 
> 
> Herbs
> 
> 
>