GT5 physics model - how complex is it?

silicon1138

silicon1138

305
France
Toulon
Hi. This morning i really got to thinking about the physics model used my PD. It's pretty mind bending the more i think about it. Has Kaz ever talked publicly about what elements are involved in his model? I assume there must be a standard model they apply to each car and then they must adjust certain parameters for each specific car, but that alone really started to tax my brain thinking about it, and led me to this topic. Certain things are quite obvious i guess, like weight and perhaps suspension/pitch/roll, but then we move into very specific characteristics, like torque, or gearing etc. How the heck do they implement such things?
I'd love to know just how complex their model is, and i'd love to hear back if anyone can shed any more light on this for me.

I'm looking forward to feeling the new physic model that Kaz mentioned - it was already pretty amazing. It's going to have an effect on all previous lap times i think.

Thanks in advance 👍
 
That's why i asked if anyone knew if Kaz had ever publicly talked about the aspects involved. Obviously PD are not going to disclose their 'secret recipe' so to speak, but they could speak in more general terms.
 
silicon1138
I assume there must be a standard model they apply to each car and then they must adjust certain parameters for each specific car, but that alone really started to tax my brain thinking about it, and led me to this topic.
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The way it usually works is, you have equations (the physics) and then parameters (the cars). Each car is a set of parameters that is fed into the physics, and the results is racing on your screen.

Certain things are quite obvious i guess, like weight and perhaps suspension/pitch/roll, but then we move into very specific characteristics, like torque, or gearing etc. How the heck do they implement such things?
I'd love to know just how complex their model is, and i'd love to hear back if anyone can shed any more light on this for me.
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It's just numbers. Weight is a number. Suspension pitch and roll are not parameters to be input, they would calculated by the physics engine when the car is in motion. Torque and gearing are just numbers.
 
they’ve even managed to accurately reflect the differences between a Mercedes SL 600 and the Mercedes SL 55, which is hard enough to do in real life.

There’s more, too. If you take a banked curve in the Bentley Le Mans car flat out, you’ll be fine. If you back off, even a little bit, you lose the aerodynamic grip and end up spinning.
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That's from Clarkson's review of GT4. Amazing when you consider they threw all their legacy code when they got their dev kits for the ps3.

Personally for me, the thing that ticks it for me is that even playing on a controller you really can feel the car on the road and hence can respond so easily to any change in the car handling. To answer the OP's case, i don't think PD is going to disclose anything about their physics engine. They are famously schtum it comes to in house secrets. Another reason why they do not outsource game development
 
Exorcet
To be honest, I think that's all marketing. Any mention of praise for GT's aerodynamics really should be taken as suspect.
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Only it's not marketing, it's for real. Try taking lexus ISf on the ring with racing hard/sports hard and see for yourself
 
vandaliser
Only it's not marketing, it's for real. Try taking lexus ISf on the ring with racing hard/sports hard and see for yourself
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What am I supposed to see? There are numerous flaws/omissions to be seen in the physics. Constant lateral grip, virtually no induced drag from aerodynamics, no brake fade/temp, tuning suspension can sometimes be nothing like real life.

GT5 is fun, and it's a decent simulator, but it's still a few steps off from reality.
 
Exorcet
What am I supposed to see? There are numerous flaws/omissions to be seen in the physics. Constant lateral grip, virtually no induced drag from aerodynamics, no brake fade/temp, tuning suspension can sometimes be nothing like real life.

GT5 is fun, and it's a decent simulator, but it's still a few steps off from reality.
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No grip from aerodynamics? Whenever I want to drive faster in the fast corners in Monza i increase the downforce and the car gets faster through the corners, or i can drive closer to the apex, instead of sliding out of the corner. When driving slower the tires usually generate enough grip to make up for the loss of grip through downforce.
 
Tires can never make up enough grip to negate loss of downforce. Tires gain grip with normal force.

And I did not say there was no grip from aero, I said there was no drag. It doesn't matter if you're maxxed or minned on downforce, your top speed varies by ~2% at most.
 
Exorcet
Tires can never make up enough grip to negate loss of downforce. Tires gain grip with normal force.

And I did not say there was no grip from aero, I said there was no drag. It doesn't matter if you're maxxed or minned on downforce, your top speed varies by ~2% at most.
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This is very true we have tested with multiple cars with max downforce will be on Avg 3-7 mph slower then with minimal downforce. Also The slipstream effect greatly exaggerated.

I still love GT5 and it's much more of a simulator then other console games. It just consoles in their current state can't match reality yet.
 
Why come the hotter the tires get the LESS grip you have?

Why come my brake don't fade?

Why come the engines horsepower/torque and rpm balance are unrealistically tuned when you max them on certain cars so that I lose traction at high rpm and not at low rpm?

Why come the antiroll bars not work right?

Why come when I downshift and hit the rev limiter I lose all engine braking? Does my transmission suddenly disengage from the universe when the rev limiter is hit?

Why come you don't have tattoo?
 
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The physics are easy to model, they are just numbers and simple mathematics. The graphics are the biggest limiting factor on consoles since they are pathetically weak in that regard.
 
jimlad_jones
The physics are easy to model, they are just numbers and simple mathematics. The graphics are the biggest limiting factor on consoles since they are pathetically weak in that regard.
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Lol, you have literally no idea how complex and demanding a realistic physics model actually could be. The tyre alone is unfathomably complicated, whilst also being the most crucial part.
Gt5, like all current simulations, simplifies things, a lot.

Gt5 doesn't quite capture weight transfer as well as previous versions imo (this shows visually too, cars do not pitch or roll enough, in general). It also feels a bit "safe" on corner entry.

I also have to have an issue with any sim that handles smoke generation in the way gt5 does.
 
ampire
Why come the hotter the tires get the LESS grip you have?
White = optimum temperature/hot great grip Red = too hot/loss off grip

Why come my brake don't fade?
GT5 doesn't have brake physics model

Why come the engines horsepower/torque and rpm balance are unrealistically tuned when you max them on certain cars so that I lose traction at high rpm and not at low rpm?
Why do you max the cars out then? When you (for example) shave 400kilos of a car don't expect realism

Why come the antiroll bars not work right?
It's a known bug, the settings are reversed

Why come when I downshift and hit the rev limiter I lose all engine braking? Does my transmission suddenly disengage from the universe when the rev limiter is hit?
Use the clutch = problem solved

Why come you don't have tattoo?
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On topic - I don't know but it's amazing.
And it's not "just numbers", it's much more than that.
I mean, for example - Zonda feels twitchy as it should, 458 has that bit of high speed slide, McLaren F1 is perfect (again, as in real life), not to mention GT-R, 8C Competizione is horrible and has all the attributes of a real life 8C (delay in transmission, bad handling etc), MP4-12C apparently feels just as it should in real life.
Some car's aren't done good (for example Lancer Evo X) but 95% of the cars are spot on.
Some things aren't done great (such as tyre physics, aerodynamics) but overal it's great and by far the best on consoles.
 
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Tire model tends to be the most complex system in these sims/games. It's a bit worrying about GT5 that we can't see or change the tire pressures and can't observe the tire temperature spread across the tire (even many of the amateur racers measure the temperature spread of tires to help in adjusting pressure and camber). After all everything the car does happens through those tires.
 
ampire
Why come the hotter the tires get the LESS grip you have?

Why come my brake don't fade?

Why come the engines horsepower/torque and rpm balance are unrealistically tuned when you max them on certain cars so that I lose traction at high rpm and not at low rpm?

Why come the antiroll bars not work right?

Why come when I downshift and hit the rev limiter I lose all engine braking? Does my transmission suddenly disengage from the universe when the rev limiter is hit?

Why come you don't have tattoo?
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Why come you can't use proper grammer?
 
Handling physics are very good imo, until you make contact with a wall, then they suddenly go backwards (no, really...).
 
PD uses approximately 80 variables for each car, give or take, depending on the car.

It takes an engineer who knows the car most of a day to calculate them all for PD, but some cars aren't real and some are not easily accessed now (they either are virtual cars (i.e. the NIKE car in GT4), or some of them will never be available to PD again (i.e. Stephan Papadakis' GT Award car), so they can only go forward using the values they already have). If a parameter is not available, for whatever reason. they may have to just make some a value up to fit the car model, in those cases.

PD also starts fudging numbers away from reality when we change parts.

Pretty amazing what PD can do with a bunch of numbers.
 
I won't start listing here all shortcomings in GT5 physics, but due to the sheer number of cars in GT there's one thing in particular that probably will never get as advanced as pc sims simulating just a few cars: the suspension model. What PD probably does is simulating in a very general way just the general differences between different suspension types (McPherson, live axles, semi-indipendent axles, double wishbones), without getting into specific details (suspension travel and preload, exact linkage points and kinematics, panhard rod lenght, etc).

They also don't appear to use proper camber and toe values for every car, although this is relatively easily available data.
 
Energizerrr
On topic - I don't know but it's amazing.
And it's not "just numbers", it's much more than that.
I mean, for example - Zonda feels twitchy as it should, 458 has that bit of high speed slide, McLaren F1 is perfect (again, as in real life), not to mention GT-R, 8C Competizione is horrible and has all the attributes of a real life 8C (delay in transmission, bad handling etc), MP4-12C apparently feels just as it should in real life.
Some car's aren't done good (for example Lancer Evo X) but 95% of the cars are spot on.
Some things aren't done great (such as tyre physics, aerodynamics) but overal it's great and by far the best on consoles.
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Once the tires heat up in this game you lose all grip. Completely unrealistic. In real life, if I wanted to acceleration quickly in a straight line, I would heat my tires first and my traction would be much greater.
 
ampire
Once the tires heat up in this game you lose all grip. Completely unrealistic. In real life, if I wanted to acceleration quickly in a straight line, I would heat my tires first and my traction would be much greater.
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No, you don't.

Ever heard of overheating your tires?
 
Energizerrr
ampire
...

Why come when I downshift and hit the rev limiter I lose all engine braking? Does my transmission suddenly disengage from the universe when the rev limiter is hit?
Use the clutch = problem solved

...
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I don't see how that helps at all!

I suspect the real issue is the sound samples would sound pretty hilarious beyond the rev limiter; this might be why so many games prevent over-revving in this manner. LFS uses synthesis and will happily let you over-rev to the stratosphere; GPL allows over-revving too, but uses single-sample sounds only, which were low-detail in the original release, plus the engine tended to seize rapidly (thank God for auto-clutch).

I can't think of any other game which has allowed the revs to rise above the rev-limit, but they must be out there.
 
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Sohvakettu
I think i remember blowing an engine or two because of over-revving the engine because of miss shifts in GTR2.
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Oh I know that game had engine damage from "over-revving", but it also had an adjustable (within a very fine range) rev-limiter for most cars, basically setting how "hard" you were pushing the engine. I don't ever remember the revs exceeding the set rev-limit, though. Sequential shifters there, too, mostly, I think. Mis-shifting's not really a problem with them.
 
jimlad_jones
The physics are easy to model, they are just numbers and simple mathematics. The graphics are the biggest limiting factor on consoles since they are pathetically weak in that regard.
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Simple maths?

OK, read this......

http://phors.locost7.info/contents.htm


....and come back with a straight face and tell me its simple maths. The physics around the likes of tyre dynamics alone are hideously involved.

You may be getting a pop quiz as well for displaying such a huge level of understatement and over confidence. :)


Scaff
 
adeadsnipermatt
Also The slipstream effect greatly exaggerated.
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One of the things I've thought for a long time is that PD has come up with a solution that makes driving the game such a unique experience. I think they exaggerate many aspects of car dynamics specifically to make the experience feel more "real" with the limited feedback mechanisms at our disposal. If you've played many other SIMS, one thing you'll notice is that in PD's products the cars feel extremely unique. You will not, even for a second, think that your RUF Yellowbird feel awfully similar to your RUF RGT. Even though they are evolutions of the same car, and even though they both feel very RR, the are also quite different. In every other SIM I've ever played, the cars feel less unique than in the GT series, which I think is key in the attraction GT has in appealing to "car enthusiasts" and not just "motor-sport enthusiasts". The thing is, all PD has to communicate these differences are sight, sound, and FFB in a steering wheel. This isn't even close to the amount of feedback a real car gives. So, how do you communicate the uniqueness of each car? How do you communicate how drafting works (for example)? Well, you exaggerate it sufficiently that the person using your product feel the difference keenly. You make cars that are neutral very neutral, you make cars with oversteer have lots of oversteer, you make cars with a soft suspension very soft and cars with a stiff suspension very stiff, you make drafting give more of a boost in speed than it should. Thus you get the "feel" of the real car through the limited sensations available for PD to work with.

Personally, this is a method that "really works for me" because that's exactly the experience I'm looking for: I want to know "what does driving an AC Cobra feel like? What does driving a Lancia Stratos feel like? etc. I don't know how complex it is, but however PD does it, it is very convincing.
 
neema_t
Exactly, hot is good but too hot is bad.
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I assume you guys do not use traction control. I don't either.
If you step on the gas even a small amount then let off the tire indicator turns red, right? Then it would make sense the next time you get on it it it would provide better traction assuming the tires are new. Take a look at any staging area for drag racing.

In this game, the tire heats up and always overheats.
 

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