So in my quest to figure out how things work (endless quest) I ran across this interview with Brian Beckman who helped with the tire physics in Forza. I thought I'd pass it along to the forum.

I think it helps to explain why there are jaggiez in Forza 2..lol. Most of the processor AND GPU is busy doing math.

http://beta.channel9.msdn.com/Media/Brian-Beckman-The-Physics-in-Games-Real-Time-Simulation-Explained/

Forza is the first racing game I've ever played where the cars actually handle like real cars. 100% undiluted awesome. That said, they REALLY need some new tracks.

Forza is the shizz!!!

forza physics is very good. Every car feels different and even though I've never driven most of the cars, cars like porsches really do drive like I think they should.

Forza is the first racing game I've ever played where the cars actually handle like real cars. 100% undiluted awesome.

I agree which is why I wanted to know more about how it works.

A friend of mine plays a lot of PC sims and when I mentioned that fuel load has an effect on handling he said that they have been doing that in PCs since 1989.

Well that is true, but not to the levels that they are now. Not only does fuel load play a role in Forza, but also gas tank location. This is not simulated by just plugging in some static number, but rather it is calculated on the fly.

The gas tank example is just a small piece to the 9000 parameters each car has in Forza that play a role in the physics model.

Why cant you change how much fuel you have at the beginning of each race like PC sims though. Thats one of the few things that has bugged me about forza

Forza 2 really does have some amazing physics. It's a shame it does not have a larger following. It's perhaps a bit too sim focused.

Sadly if they use some of the resources for a more polished look than the behind the scenes calculations, they'd likely sell a lot more and get reviewed better.

Howerver, I rather that not be the case!

If you want to see bad physics in action, I highly recommend NASCAR 08. I was doing a few laps at my buddy's house earlier around Sears Point. I actually managed to FLIP the car by use the inside curbing on a corner like you should. I was simply amazed by this! Not to mention some curbs while appearing to be such have 0 effect on the car. Now that's amazing! And I have many many laps around Sears IRL to know what the track is like!

I agree that if it were better eye candy it would gain a bigger following. Thats what PGR is for.

In that interview he talks about how sim people are looking for as close to as exact simulation as possible and I think that is totally true. When I have friends over they usually wreck on the first turn in forza.

The biggest problem with Forza is a lack of interesting places to race. I'm into the game now and I'm already getting a bit tired of some of the courses, even though I appreciate the larger ones quite a bit, the smaller ones like Tsukuba (sp) Circuit and such, man, if I never had to race those again....

I do miss some of the "Fantasy Tracks" that GT4 had......they were some of the most fun to race because of their scenery and diverse road structure.

Great interview. Thanks for sharing!

Forza is awesome. It is definitely technical, but the constant framerate rocks in my opinion.

Usually I'm too focused on the track to notice all the other scenery around me. It's only if I'm messing around trying to jump my car or something that I notice the scenery.

It's only if I'm messing around trying to jump my car or something that I notice the scenery.

I find that the 3d trees / track environment is nice on endourance races. I get kind of bored if Im in the lead so I like to sight see.

Usually thats when I stop paying attention to the actual track and wreck though...haha.

oh and watch the interview and stay on topic. This thread was supposed to be about teh physics calculations!

Sim or not, anyone can still have fun with the game. There are various levels of player skill on LIVE. You'll either get the racing enthusiasts, the demo derby crowd, or somewhere in between.

Or, after a few weeks of acclimating to a few cars in single player, they all become easier to handle.

One gripe, however is when you clip the wall and the car 98% of the time spins the opposite direction. IE, you are driving 45 mph, you feather the wall on the right, and the car quickly rotates clockwise.

I like flying down some of those straightaways and passing the 300 RV's in the infield....stuff like that makes me think I'm in an actual race.. :)

All I need are rednecks throwing beer cans at me!

oh and watch the interview and stay on topic. This thread was supposed to be about teh physics calculations!

Dude...I'm at work so watching a video isn't high on my prioriti! :) (reading this and other forums wastes enough of my time)

I'd much rather use this as an excuse to relay my pleasure playing Forza. :cool:

One gripe, however is when you clip the wall and the car 98% of the time spins the opposite direction. IE, you are driving 45 mph, you feather the wall on the right, and the car quickly rotates clockwise.

From that example I think thats what would happen. Drag would be created on the right side of your car hence pulling it more right (clockwise).

Kind of like if you get your right tires in the dirt, your car pulls to the right due to the drag?

Unless I am missing what you are saying.

I think he is saying that the likelihood of ending up facing backwards on the track during a wreck is not 50%. This part of the physics model is a bit skewed.

One would think that a 60% front balance versus 40% front balance would have a different proportion of backwards versus forwards during wrecks. But I have found in random wrecks with or without steering input that all balance cars end up facing backwards about 70% of the time.

A second physics related issue I see is that I can ram a computer opponent that is driving an unstable car (like the Cadillac CTS-V) and the computer guy keep on driving just fine. But if the computer just barely taps me, I am likely to have major damage and will probably be put into the wall. There are some high-level races (L45 I think?) where you have to be very patient to get around the front three or four cars, and the guy in fifth place fly's through a corner 30 mph faster than the field slamming into you.

In other words, the computer opponents use a different physics model than humans.

A second physics related issue I see is that I can ram a computer opponent that is driving an unstable car (like the Cadillac CTS-V) and the computer guy keep on driving just fine. But if the computer just barely taps me, I am likely to have major damage and will probably be put into the wall. There are some high-level races (L45 I think?) where you have to be very patient to get around the front three or four cars, and the guy in fifth place fly's through a corner 30 mph faster than the field slamming into you.

In other words, the computer opponents use a different physics model than humans.

I have wondered about this as well! Do they drive by different rules? Do they drive with all the assists on and perfectly tuned cars?

The AI uses all assists, and only drives stock cars. The laws of physics still apply to the AI cars, they just essentially have 100% perfect disaster recovery... assumingly to stop you from winning races by spinning them out in the first corner.

The fact that you usually end up backwards I think would be correct physics. If your car spins out and you have forward momentum then your tires will be in a skid while you are turned. Once you have completely turned around to being backwards your tires are back in line with the forward momentum of your car and you regain traction, causing your spin to stop. Only once in a while will you have a huge enough spin momentum to break off that traction and keep turning.