Talk:Ragdoll physics

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Thoughts[edit]

This is mostly just stream-of-conscious and/or me being forced to make up names for things ("inverse kinematics post-processing") because I'm not sure if anyone else has named them before.

Thoughts:

  1. do we really need a list of games that use ragdoll? It's almost universal these days. It seems more sensical to have maybe a list of firsts.
  2. would it be useful to have some external links to some public-domain papers on the subject? (Thomas Jakobsen's Advanced Character Physics is on the Web, for instance.)
  3. does any of this make sense? If anyone who has absolutely no clue how physics in games work could take a read through and tell me which parts don't make any sense, I'd gladly clean them up.

Kyle Davis 07:06, Oct 27, 2004 (UTC)

Hey, really nice. :) 1) No, we don't. List of firsts, maybe just merged in the body text, would be the best. 2) Yes, it would! Please add if you know some good papers. 3) To me it seems to be very well written. --ZeroOne 19:12, 27 Oct 2004 (UTC)


  1. I don't think we need a list of games unless they are noteable in the development of ragdoll physics. These games should not be listed, they should be incorperated and explained in the article itself.
  2. If they are public domain papers, could we incorperate them into the article itself? If not, why don't we cite them?
  3. I don't think the article if very well written. Someone who does not have previous knowledge of the subject would not find much useful information in the article.

Jellocube27 18:20, 18 June 2006 (UTC)[reply]

Incorrect claim[edit]

Removed claim that prescripted animation uses less memory than a ragdoll physics animation. A prescripted animation must have bone locations for every key frame at the very least. Ragdoll physics only require the current state of the bones to remain in memory. --MidoriKid 01:43, 2 September 2005 (UTC)[reply]

Alternate link[edit]

GamaSutra requires registration, it would be better to link to the article somewhere else. Is this the article in question? --GalFisk 21:19, 21 February 2006 (UTC)[reply]

Issues[edit]

This needs some work. 1) Verlet integration is just an integration method, like Runge-Kutta, Euler, or the implicit methods. It's only part of a "ragdoll physics" system. 2) The two basic approaches are "spring-damper" methods and "impulse-constraint" methods. Early systems, like Trespasser, used spring-damper, but badly. We (www.animats.com) did a spring-damper ragdoll system that worked in 1997, but it wasn't real time. Most newer systems, like Havok's, use impulse-constraint methods. See Dave Baraff's SIGGRAPH papers for those. Jacobson's approach is spring-damper again. 3) The hard part in all this is keeping the system from going unstable. Most serious work revolves around maintaining numerical stability during collisions. This leads into discussions of solution methods for stiff systems of differential equations, a difficult subject worth an article of its own.

Should new technical material in this area go in "game physics" or "ragdoll physics"? Right now, "ragdoll physics" has more technical detail than "game physics", which is a stub. --Nagle 20:07, 6 March 2006 (UTC)[reply]

Added a picture from one of our first ragdoll simulations, from 1997. This introduced what is now a cliche of ragdoll physics, falling downstairs. This may be the first successful ragdoll. If anyone knows of anything earlier than 1997, please note that. --Nagle 03:04, 8 March 2006 (UTC)[reply]

Suggest not adding names that use this technology[edit]

Adding names of games that use this technology is probably unnecessary. It's so widespread that the full list would be huge and would clutter the article. I've removed a short list. --John Nagle 18:56, 5 April 2006 (UTC)[reply]

  • I'll second this. I'm also unsure of whether we need such a full list of "try it" demos. --Kyle Davis 22:58, 7 April 2006 (UTC)[reply]
  • An anon just added a big list of games using ragdolls. What's the consensus on this? Keep or delete? --John Nagle 02:00, 3 May 2006 (UTC)[reply]
Oops - just read this. See my note below. I agree with John Nagle about the spread of ragdoll physics. It's practically the norm already, and will only become more so. Anyway, to me a list of engines (plus selected titles, perhaps the first that made use of them) seems better. Certainly in terms of keeping the article at a reasonable length. I've started below (though have left too many titles in there). Cheers, --Plumbago 12:46, 23 May 2006 (UTC)[reply]
I agree that adding long lists of game titles to articles about game engine components is kinda pointless. The lists will never be maintained correctly and an outdated list is worse than no list. Scenario: Reader comes here wondering about whether game X uses ragdoll physics - sees that X is not on our list - concludes (incorrectly) that X doesn't use ragdoll when in fact we just didn't notice or hadn't remembered to add it. I'm inclined to remove these lists from all of the game engine articles for that reason. If there is great value to someone to preserve this information then a better approach would be to go to the page about the game and list there the game engine components and technologies that it uses. That way, if the information is present, it's correct and will likely stay correct because published games don't change their game engines over time (unless we're talking sequels or ports to other platforms of course). SteveBaker 13:54, 11 October 2006 (UTC)[reply]

Ragdoll engines[edit]

The current list of games using ragdoll physics is getting rather long. I propose that, instead, we list engines that have ragdoll physics, plus a short (-ish) list of titles using them. For instance :

At the moment there are a lot of titles (some quite famous ones) for which there's no engine listed. It might be better to only add a title if detail about its engine can also be added. Anyway, just a thought. Cheers, --Plumbago 12:42, 23 May 2006 (UTC)[reply]

I've now hacked the list back to that above (plus a few new Havok titles). It was getting crazy long, with titles being added for which no engine was specified. The list that's there now could be culled further (especially for the Havok engine), but it probably would be helpful to add new titles only if they add a new engine (or augment the shorter title lists). --Plumbago 12:10, 27 June 2006 (UTC)[reply]

I don't think that we need a list of all the games so far that have rag dolls. Ragdolls in games are becoming very popular. Pixels and truely 3d graphics were rare at the time of quake, but by the time Half-Life came out a list games with true 3d graphics would be overwhelming. I feel as if that is the direction we will be headed if the list of ragdoll-games is left. If there are objections to this, please say so now. Jellocube27 17:24, 8 July 2006 (UTC)[reply]

I agree. It's now a standard feature. --John Nagle 17:37, 8 July 2006 (UTC)[reply]
I think the lists I added should be trimmed down to a few (three or so) of the most notable titles - those where ragdoll physics were a new feature. Not knowing most of the games in the list I originally hacked, I didn't want to do this myself. I think for the page to make some historic sense in the future, some titles should remain, but not the long lists I left in. Cheers, --Plumbago 21:28, 8 July 2006 (UTC)[reply]

All right, then we are going to need some defining qualities of what makes a landmark in the development of ragdoll physics. I, personally, am not knowledgable on the subject of physics simulations. If anyone is, please post what you know about the development stages of ragdoll physics-- obviously the tecniques used in Tresspasser aren't used in the newest Half-Life 2 expansion. Jellocube27 17:49, 9 July 2006 (UTC)[reply]

I could write more about that, but the main audience here seems to be gamers, not physics engine designers. How many people want to hear about linear complementarity problem solvers, integration of stiff systems of nonlinear differential equations, the GJK algorithm, impulse/constraint vs. spring/damper approaches, static indeterminacy, and similar topics? For that, you start by reading "Physics for Game Developers" or one of the other books on the subject. Besides, I'm too close to the subject. --John Nagle 03:19, 12 July 2006 (UTC)[reply]
This being Wikipedia, writing an article for the interest of any single "audience" seems a bit absurd for me. I feel that as long as the complex techniques you have mentioned are explained in a straightforward and clarified manner, and relevant to the subject of Rag Doll physics, that they belong in this article. You are correct in saying that right now, this article mainly appeals to gamers. Because of this, I suggest the article either is made to incorperate detailed explanations of the physics used in rag dolls, or broken into two articles: the first being this, the second being a more thorough explanation. Jellocube27 17:59, 12 July 2006 (UTC)[reply]

Game List[edit]

I think someone should try to list some more--DogPHman 11:33, 5 August 2006 (UTC)[reply]

I strongly disagree - I think we should delete these lists. They are never comprehensive and an omission is 'negative information' - which is to be avoided like the plague. It would be better to go to each game and add a 'Technologies Used' section that lists the technologies that game is known to use. That way, as each new game is added, we get the relevent information kept together. SteveBaker 13:57, 11 October 2006 (UTC)[reply]
I have moved the list of games that support this technology over to List of games using physics engines so it won't clutter up this article. SteveBaker 14:28, 16 October 2006 (UTC)[reply]

Proposed Merger with Tetka[edit]

I don't see much useful information in the Tetka article that we need here. It'll just clutter up a perfectly good article with junk about some internet meme. SteveBaker 14:00, 11 October 2006 (UTC) OH noes I was the author of that article :( --212.139.60.238 17:44, 7 May 2007 (UTC) (Importancenn)[reply]

Verlet Integration[edit]

I'm under the impression, for some reason I'm not sure of, that Verlet integration is quite a common way of implementing 2D ragdolls. At the very least, I'm 95% sure Rag Doll Kung Fu uses it. If anyone knows a bit more about this, it probably deserves a mention. --203.206.183.160 19:22, 23 February 2007 (UTC)[reply]

The public domain paper[edit]

this is wikipedia and we still need to cite sources, remember? i've added back the Thomas Jakobsen article. --Witchinghour 15:27, 1 May 2007 (UTC)[reply]

Added references to spring/damper and constraint system papers. Really should cite a later Baraff paper, though, from when he finally got the linear complementarity solver thing worked out around 2000. Try to find a ref that isn't a pay site. --John Nagle 17:20, 5 October 2007 (UTC)[reply]

nip?[edit]

The third paragraph includes the phrase "...leading to a character with a nip collapsing much like a toy rag doll...". What the heck is a nip in this context? This needs to be explained (perhaps via a link) or changed. Herostratus (talk) 19:55, 28 December 2007 (UTC)[reply]

Added information[edit]

I added some info on procedural animation tech, i.e. Euphoria et al, but this page still needs some references to ACTUAL papers on the subject, rather than more examples of new game tech from GTA IV fanboys (i.e, moi). Ho Hum. Better than pretending it doesn't exist, I guess. Would love to see someone expand on it. :-) love from some anonymous dousche — Preceding unsigned comment added by 60.240.77.211 (talk • contribs)

"polar", not "popular" re Trespasser[edit]

Someone changed "polar" to "popular" regarding the Trespasser section. "Polar" was intended. Some reviewers wrote good things about the game. Other reviews had lines like "worst game I ever played". The GDC Postmortem made it clear that the game physics was badly broken. Things would go flying off into space. This was spring/damper physics before means were found to make it stable. --John Nagle (talk) 23:10, 28 April 2008 (UTC)[reply]

What does this mean?[edit]

"Recent procedural animation technologies, such as those found in NaturalMotion's Euphoria software, have allowed the development of games that rely heavily on the suspension of disbelief"

What does suspension of disbelief have to do with anything? How do any of those games listed rely heavily on it? This sentence seems weird and redundant.70.71.234.123 (talk) 22:27, 14 January 2019 (UTC)[reply]

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