Comments on: Zen of Networked Physics http://gafferongames.com/2004/12/28/zen-of-networked-physics/ Glenn Fiedler's Game Development Articles and Tutorials Tue, 31 Jan 2012 03:56:23 +0000 hourly 1 http://wordpress.org/?v=3.3.1 By: Glenn Fiedler http://gafferongames.com/2004/12/28/zen-of-networked-physics/#comment-26 Glenn Fiedler Mon, 22 Feb 2010 18:16:07 +0000 http://www.gaffer.org/archives/7#comment-26 fixed! fixed!

]]> By: fred http://gafferongames.com/2004/12/28/zen-of-networked-physics/#comment-25 fred Mon, 22 Feb 2010 09:03:52 +0000 http://www.gaffer.org/archives/7#comment-25 Hi Gaffer, great site but the download link doesnt seem to work. could you email it to me or send me a link? thanks! Fred Hi Gaffer,
great site but the download link doesnt seem to work. could you email it to me or send me a link?

thanks!

Fred

]]> By: Nobody’s Life » “Математиката” в мултиплейър варианта на игрите http://gafferongames.com/2004/12/28/zen-of-networked-physics/#comment-24 Nobody’s Life » “Математиката” в мултиплейър варианта на игрите Tue, 14 Oct 2008 11:10:00 +0000 http://www.gaffer.org/archives/7#comment-24 [...] иде реч (освен общата култура). Още няколко подобни текста си струват усилието да се прочетат. These icons link to social [...] [...] иде реч (освен общата култура). Още няколко подобни текста си струват усилието да се прочетат. These icons link to social [...]

]]> By: Glenn Fiedler http://gafferongames.com/2004/12/28/zen-of-networked-physics/#comment-23 Glenn Fiedler Sat, 17 Feb 2007 19:38:20 +0000 http://www.gaffer.org/archives/7#comment-23 its certainly possible, but you still have to deal with the differences of FP hardware implementation - it would also be quite slow because you'd have to explicitly store to memory and reload into FP to truncate precision at each step i'd be inclined to just write my own 64bit integer based routines, or emulated floating point routines in software if i were to take this approach but i wont because there are other ways of handling the problem! dont rely on absolute determinism! - just trust your result to be *mostly* the same and have the ability to correct for error over time as it drifts cheers its certainly possible, but you still have to deal with the differences of FP hardware implementation – it would also be quite slow because you’d have to explicitly store to memory and reload into FP to truncate precision at each step

i’d be inclined to just write my own 64bit integer based routines, or emulated floating point routines in software if i were to take this approach

but i wont because there are other ways of handling the problem! dont rely on absolute determinism! – just trust your result to be *mostly* the same and have the ability to correct for error over time as it drifts

cheers

]]> By: Ian Smith http://gafferongames.com/2004/12/28/zen-of-networked-physics/#comment-22 Ian Smith Tue, 23 Jan 2007 02:03:42 +0000 http://www.gaffer.org/archives/7#comment-22 Would it be possible to use rounding of FP values to create an absolutely deterministic system even between 32bit and 64bit systems? I think it would be possible and the overall loss of precision should be completely irrelevant. In essence we would trade precision for the ability to reproduce results. Maybe 28bit precision? Rounding would need to be done at significant points to avoid compounding errors. Having a zero fill system for the last 2-4 bits would likely not impact performance too much on well designed processors. Would it be possible to use rounding of FP values to create an absolutely deterministic system even between 32bit and 64bit systems? I think it would be possible and the overall loss of precision should be completely irrelevant. In essence we would trade precision for the ability to reproduce results. Maybe 28bit precision? Rounding would need to be done at significant points to avoid compounding errors. Having a zero fill system for the last 2-4 bits would likely not impact performance too much on well designed processors.

]]> By: Glenn Fiedler http://gafferongames.com/2004/12/28/zen-of-networked-physics/#comment-21 Glenn Fiedler Wed, 11 Oct 2006 17:19:56 +0000 http://www.gaffer.org/archives/7#comment-21 back online now, cheers back online now, cheers

]]> By: Glenn Fiedler http://gafferongames.com/2004/12/28/zen-of-networked-physics/#comment-20 Glenn Fiedler Tue, 03 Oct 2006 17:33:46 +0000 http://www.gaffer.org/archives/7#comment-20 yes. unfortunately the download link is broken since ace-host.net deleted my entire site last weekend, i'll have it back online shortly -- i have to rebuild it from backups cheers yes. unfortunately the download link is broken since ace-host.net deleted my entire site last weekend, i’ll have it back online shortly — i have to rebuild it from backups cheers

]]> By: Muhammet Taha http://gafferongames.com/2004/12/28/zen-of-networked-physics/#comment-19 Muhammet Taha Tue, 03 Oct 2006 11:36:06 +0000 http://www.gaffer.org/archives/7#comment-19 check the download link please.. check the download link please..

]]> By: Glenn Fiedler http://gafferongames.com/2004/12/28/zen-of-networked-physics/#comment-18 Glenn Fiedler Thu, 28 Sep 2006 18:20:48 +0000 http://www.gaffer.org/archives/7#comment-18 yes it is true that it is virtually impossible to get deterministic floating point across different machines, if you absolutely require determinism, one solution is to use integer math, another is to write your own floating point emulation implementation -- trading speed for deterministic behavior my recommended solution is that you dont require exact determinism (eg. dont do lockstep networking), but instead follow the techniques in zen of network physics, and allow for a rewind and correction phase when things desync for any number of reasons, packet loss, non-determinism (which you should MINIMIZE but can never really eliminate...), and so on. cheers yes it is true that it is virtually impossible to get deterministic floating point across different machines,

if you absolutely require determinism, one solution is to use integer math, another is to write your own floating point emulation implementation — trading speed for deterministic behavior

my recommended solution is that you dont require exact determinism (eg. dont do lockstep networking), but instead follow the techniques in zen of network physics, and allow for a rewind and correction phase when things desync for any number of reasons, packet loss, non-determinism (which you should MINIMIZE but can never really eliminate…), and so on.

cheers

]]> By: carlos http://gafferongames.com/2004/12/28/zen-of-networked-physics/#comment-17 carlos Thu, 28 Sep 2006 07:57:36 +0000 http://www.gaffer.org/archives/7#comment-17 Hi! Thanks for that interesting article. I'm trying to make a scene with deterministic behavior based on input's user on Windows, but I founded a problem... float precision. When I launch two executions in the same machine using the same recorded input stream I obtain different results. How can fix it (avoid use of fixed point) ? Using _controlfp_s or similar perhaps? Thanks a lot. Hi!
Thanks for that interesting article.
I’m trying to make a scene with deterministic behavior based on input’s user on Windows, but I founded a problem… float precision.
When I launch two executions in the same machine using the same recorded input stream I obtain different results.
How can fix it (avoid use of fixed point) ? Using _controlfp_s or similar perhaps?
Thanks a lot.

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