Re: Inside a simulator question

Ian, I've been recently coding a model that works quite well (if I do say so myself). The "GPL-Handling Question -Physics model" thread is a place to look for a discussion on a problem I was having calculating tire forces correctly. I just posted a lengthy reply that gets into the problems in detail. It also contains the general workings of the model. If you're interested in seeing it, you'll need to set your Preferences to not block out any long messages. It shows up as "GPL-Handling Question -Physics model Warning, long post". Cheers, Todd Wasson http://PerformanceSimulations.Com

Hi, I was wondering if we could a (more scientific) thread going on how the internals of such a game are constructed, if anyone knows. What are the basic elements and how do they interact ? People talk about the physics model, what does this actually mean, modelling the motion of body under Newtonian forces ? I realise it's complex with friction etc. Maybe i should say I have a degree in Physics and Computer science so might be able to understand the theory but have little intuition to how the internals of something like GP2/GPL could look like. I would guess the code is a marriage of some modelling with the track itself. The AI aspect is interesting but not exactly central. What would be nice would a public domain implementation of a body undergoing forces like acceleration, braking etc that we could look at. please send a URL (code pointers) if you have any. -- Ian

As I mentioned in a post a couple of days ago, I've just set up a website (early days still!) that tries to cover some of the 'physics modelling' issues. More detail will be added soon. www.callnet0800.co.uk/myhome/nreverett/gplindex.htm Hope this helps. Cheers, Neil * Sent from RemarQ http://www.remarq.com The Internet's Discussion Network * The fastest and easiest way to search and participate in Usenet - Free!

Neil <[email hidden]> writes:

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> As I mentioned in a post a couple of days ago, I've just set up > a website (early days still!) that tries to cover some of > the 'physics modelling' issues. More detail will be added soon. > > www.callnet0800.co.uk/myhome/nreverett/gplindex.htm > > Hope this helps.

It does, thanks alot Neil. I.

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> > Cheers, > > Neil > > * Sent from RemarQ http://www.remarq.com The Internet's Discussion Network * > The fastest and easiest way to search and participate in Usenet - Free! >

-- Ian

On 24 May 2000 12:35:39 +0200 Ian Marsh <[email hidden]> wrote: % Hi, % I was wondering if we could a (more scientific) thread going on how % the internals of such a game are constructed, if anyone knows. While it is not detailed about the code, there was an interview with David Kaemmer by John O'Keefe that "touches" on this. The URL is http://website.lineone.net/~richardn/Kaemmer.html Here is the part about what is modeled in GPL: Could you give people insight into how complex the Grand Prix Legends simulation is? For example I heard somewhere that you model the airflow into or through the engine? What are some of the most complex aspects of GPL? For the engines, I use a model for engine friction that I got from a couple of SAE papers--the friction is a function of inlet valve diameter, stroke length, etc.--and it seems to be pretty close (we have data for all these parameters for each of the cars). The most complex aspects of GPL...? How much time do you have? :-) The multi-body simulation is very accurate--each GPL car is made up of the chassis, the fuel mass (which changes), four wheels with independent hops and spins, an engine & flywheel rotor, clutch & transmission input shaft, transfer shaft, and output shaft. Each of these bodies maintains its own linear and angular momentum, basically. You can see some of this if you watch the car land on its top after flying through the air (and who hasn't seen this?)--just when the car lands, you'll see the wheels each continue to travel downwards until the springs stop them. If you jump the car in the air (the 'Ring--woohoo), you can see all the gyroscopic effects that occur when you turn the steering wheel in mid-flight, or stay on the throttle, or jump on the brakes (doh). Some might say this is overkill, but not those of us who know the kink before Schwedenkreuz. :-) The tire model is also extremely complex and accurate. There has been a lot of excellent work recently by those who have PhD's in the physics of tire and rubber friction, and we have incorporated a lot of that into the current model. The differential deserves some mention--notice that with a near open diff (85/85, with 1 clutch), you have no trouble getting inside rear wheelspin. Or try starting with one wheel on the grass and one on the road. The constraints which apply within the drivetrain are non-trivial. The collision system is pretty complex--and that's an understatement. Outside of the physics, obviously the graphics system is pretty complex, the multiplayer system design, the AI--I can't do anything but scratch the surface here, but suffice it to say that the GPL model is several orders of magnitude more complex than anything we've done before. <snip> -- **************************** Michael E. Carver ************************* Upside out, or inside down...False alarm the only game in town. [email hidden] http://www.teleport.com/~mcarver =-=-=-=-=-=-=-=-=-=-=-=-=-=-=<[ /./. [- < ]>=-=-=-=-=-=-=-=-=-=-=-=-=-=

Sorry I can't be more specific, but I believe that there is an open source simulation project going on that would be a good place to see the "guts" of the game. Try a Deja News search, or maybe someone can respond with an url. [email hidden] (Ian Marsh) wrote in <[email hidden]>:

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>Hi, > >I was wondering if we could a (more scientific) thread going on how >the internals of such a game are constructed, if anyone knows. > >What are the basic elements and how do they interact ? People talk >about the physics model, what does this actually mean, modelling the >motion of body under Newtonian forces ? I realise it's complex with >friction etc. > >Maybe i should say I have a degree in Physics and Computer science so >might be able to understand the theory but have little intuition to >how the internals of something like GP2/GPL could look like. I would >guess the code is a marriage of some modelling with the track >itself. The AI aspect is interesting but not exactly central. > >What would be nice would a public domain implementation of a body >undergoing forces like acceleration, braking etc that we could look >at. please send a URL (code pointers) if you have any. > >

-- Don Scurlock Vancouver,B.C.

"Don Scurlock" <[email hidden]> wrote in message news:8F3E6BE01dscurlock@news... > Sorry I can't be more specific, but I believe that there is an open > source simulation project going on that would be a good place to see > the "guts" of the game. Try a Deja News search, or maybe someone can > respond with an url. > >Don, I believe you are thinking of Dr. Paul Hoad's project. This is the URL: http://members.xoom.com/_XMCM/paulhoad/glGP/index.html This is not truely an open source project. Source is not available on a download at will basis. Paul is soliciting people to help, but at the moment the source is his, and effectively closed and therefore not available as a purely curiosity driven object. It is a principal of the project that source will EVENTUALLY go open. As a member of the Linux/Open Source "community" I am, however, aware of a number of driving sim/games under way. Anyone interested can go here: http://freshmeat.net/ and search around. Some of these are multiplatform, but some are Linux only. Source should be readily available for all of them. These are just the public projects. I'm personally aware of a number of projects along this line that havn't "gone public" yet. Personally I'm hoping that within a couple of years or so driving sims will have effectively "gone open source." This will have a number of effects on the sim community, not the least of which is that for a commercial vendor to compete for actual dollars they'll have to give us somthing REALLY special to pry the cold hard cash from our pockets.