Friction

[flippin_waffles]

The one thing that I can say that i've noticed very little change in games is friction. Is it a very very difficult thing to do? I can imagine it would be. I guess that would call for some seriously large coding to get all those surfaces to interact together. Does physics adress this?
It's just one of the main things I notice in every game I play, like when a character runs, their feet always slide on the ground or whatever. It's the thing that looks the least real to me, especially now. I can imagine a very immersive experience with a world full of friction. :lol:

[MDolenc]

Do you mean physics (science) or physx (aka the PPU)? Physics deals with friction of course. PhysX... Not really.
People sliding on the ground when running/walking is more of an animation/algorithmic problem then a problem with game physics. You need to ensure that feet won't move while they are in contact with ground.

[flippin_waffles]

Yes, I wondered if physx broke any barriers in regards to the physics of friction. It's much much better than it was that's for sure though. So what is involved to be able to get an object to ineract with another and exhibit friction? I guess the 2 objects would have to mesh somehow along with some massive calculations?

[MDolenc]

It's not that you need massive calculation... You need good animation algorithms. You typicaly deal with bone animation, root bone is usually somewhere in torso and then bones go down to legs and up for head and arms. You can only move your character by moving the root bone and not by moving bones in legs! This can present a serious "gliding" problem when speed of movement isn't synced with the speed of moving legs. But walking/running in a straight line is not really a problem. Turning is... That's something that's not really a solved problem. Even offline rendering guys have problems with this.

[AlStrong]

Developers of NBA games on consoles are doing a pretty good job with minimizing gliding, and their body turning while running looks pretty good.

[NIB]

Some racing games(live for speed for example) have extremely realistic and detailed friction models for the tyres and generally how the car moves(suspensions, type and shape of ground, weight distribution, etc).

[Colourless]

There have been a number of FPS' that have played around with friction with things like low friction surfaces that make you slide, but nothing particularly exciting. Movement in FPS' is hardly realistic to begin with.

[Npl]

the problem is the speed players are running in many FPSes. If you`d accurately animate the feet it would probably look like some old Mickey Mouse cartoon.
"Slow" games can afford realistic animations, but fast-paced shooters will always have sliding characters at 30km/h

[Davros]

the quake engine must of moddelled friction to some degree
because you could change the amount of it using the console "SV_FRICTION "

and nexuiz has these settings
* sv_airaccelerate
* sv_accelerate
* sv_maxspeed
* sv_maxairspeed
* set sv_friction_on_land
* set sv_airaccel_sideways_friction
* set sv_airaccel_qw

[nintenho]

FORZA 2

http://dpad.gotfrag.com/xbox360/forums/thread/273647/
The game runs over 9000 physics computations, 360 times per second. The temperature of the outer tire affects the temperature of the inner tire which affects the core pressure which affects the friction coefficient which affects centrifugal pull around curves which affects acceleration and drifting, and.... you get the idea. Everything is connected, and it only works because everything is right. EVERY. THING. IS. RIGHT.

The track at Sebring is built on an old airstrip made of concrete blocks that sit unevenly. One block may be two inches higher than another, another block may be four inches away from another, etc. It's not a ride you want to make with hemhorroids. But at 180 MPH and 60 FPS, you can cover over four cracks in the span of 1/60th of a second. If the physics only ran at 60 FPS along with the frame rate, you wouldn't even know those important cracks are there. They [the physics in Forza 2] run the physics at six TIMES the frame rate to make sure you feel every f'n crack on that track, and you do. Every f'n one.

More about realism here in a second, but I didn't want to forget about the cars. Over 300 cars, engine swaps, drive train swaps, hundreds of real aftermarket mods and for cars with little aftermarket mod support, "Forza" branded aftermarket mods are available so those cars can "play" too.

OK, realism: Forza didn't use any car manufacturer's specs. Sometimes, they're... off. So every spec was measured by the Forza team themselves, with over 1000 vehicles measured using different configurations of the aftermarket parts. A typical solution would be a linear equation for tracking improvements through upgrades. Forza uses a non-linear equation that provides a more realistic final performance and performance rating.

Case in point: one car measured ended up with vibration in the front end. The team was certain they screwed up somewhere because there wouldn't be a car released with this odd vibration. Three months later, Car and Driver did a review of the car... and docked it for having the vibration. The Forza model generated a spec that was more real than the actual manufacturer's spec, and revealed a flaw that the mfg. wasn't even aware of, and they were later proven as being right on the money.

Do you have any idea how significant that is? That means this is more than just a "who's car is cartooneyer" issue. That means that the Forza physics model is more accurate than most of the models used by the design teamsof the cars themselves. Forza is a lot of fun, but under the hood... it's f'n SCIENCE, baybee. Nothing fake, nothing made up, nothing manually filled in to compensate for something that isn't right. They wrote the math, ran the program, and it's f'n RIGHT.[/B]

That's probably the most impressive.

[silent_guy]

Do you have any idea how significant that is? That means this is more than just a "who's car is cartooneyer" issue. That means that the Forza physics model is more accurate than most of the models used by the design teamsof the cars themselves. Forza is a lot of fun, but under the hood... it's f'n SCIENCE, baybee. Nothing fake, nothing made up, nothing manually filled in to compensate for something that isn't right. They wrote the math, ran the program, and it's f'n RIGHT.[/b]

That's probably the most impressive.

It's impressive that they measured the characteristics of all those cars (must have been fun!). But to claim then that their models are more accurate than those of the manufacturers is a bit of a stretch. While in college, I once visited a car manufacturer research facility where the showed how they tuned the sound of an engine by modeling pretty much everything and simulating different power conditions etc. The amount of modeling and measurement data that is gathered during the development of a new car is staggering, takes months, if not years, to accumulate and is very accurate.

It's more likely a combination of the Forza marketing team playing up their abilities... and the car manufacturers marketing team trying to hide its weaknesses. :wink:

In combination with a good general physics model of a car (see also X-plane (http://www.x-plane.com/about.html)), you probably don't need too many measurements to get within 95% of the real life behavior. Should be good enough for any racing game.

[nintenho]

That's somebody's impressions, not a PR release and they were noticing a vibration in the front of the car and the company must have been willing to let the car vibrate because Car & Driver's impressions showed the vibration as a problem.

[silent_guy]

That's somebody's impressions, not a PR release and they were noticing a vibration in the front of the car and the company must have been willing to let the car vibrate because Car & Driver's impressions showed the vibration as a problem.

Sure.

But from there, it's a huge leap to claim, as written in the article, that the models of the car manufacturer were less accurate and didn't reveal this and that the car manufacturer wasn't aware of the flaw.

[nintenho]

Yeah that part was BS but I'm just saying how far they took modeling everything.

[NIB]

Live for speed is vastly superior than any other racing sim IMO. Forza 2 isnt out, but forza 1 is inferior to lfs and i am pretty sure it will be the same story with forza 2. Sorry to break this to you, but lfs had this type of tire simulation(different temperatures for inner, center, outer side of the tire) for a long time now.

Lfs might not have the best graphics in the world(they are just ok), it might not have real cars(except for 1-2) but if you want realistic driving, lfs is what you want.