Path: chuka.playstation.co.uk!news From: Alex Herbert Newsgroups: scee.yaroze.programming.2d_graphics Subject: Re: Animating sprites Date: Sat, 16 May 1998 23:12:31 +0000 Organization: PlayStation Net Yaroze (SCEE) Lines: 63 Message-ID: <355E0F4F.1CFAECA7@ndirect.co.uk> References: <01bd7ac4$e4eda480$7397989e@antonio.lightwork> <01bd803a$2c971800$80c809c0@antonio.lightwork> Reply-To: aherbert@ndirect.co.uk NNTP-Posting-Host: dialin0-31.ndirect.co.uk Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Mailer: Mozilla 4.04 [en] (Win95; I) To: Martin Swaine 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