General AC Modding Manual 3.0

[Nitro McClean]

In your manual you give a detailed explanation about the theory behind Centre of gravity / center of mass. But you don't mention how to change this in the AC files. In which file and whitch line can I change this?

 

[Stereo]

In your manual you give a detailed explanation about the theory behind Centre of gravity / center of mass. But you don't mention how to change this in the AC files. In which file and whitch line can I change this?

You can't change it which should be the point of the theory? The center of mass is always at 0, you set everything else relative to that (graphics from car.ini, suspension from suspension.ini, and most other stuff follows the graphics offset)

 

[Nitro McClean]

You can't change it which should be the point of the theory? The center of mass is always at 0, you set everything else relative to that (graphics from car.ini, suspension from suspension.ini, and most other stuff follows the graphics offset)

Why should it be that way? So you have to take that in mind when creating the whole car. I got into this because karts in AC are very bad.
A kart has a rigid rear axle without a differential. As a result, the rear wheels of a kart twist when you normally drive through the bend and you experience a lot of understeer. Real kart drivers keep their bodies outward when cornering. This causes the rear wheel on the inside of the bend to come off the ground. This causes the kart to go through the bend on three wheels and the understeer is gone. That is difficult to imitate in a simulator. I managed to do it in rFactor by raising the center of gravity a little. This also makes the kart go around the bend in rFactor on three wheels. It must be very accurate to simulate this properly.
I also want this in AC, but I have no idea how to do this now.

 

[brotto marco]

In your manual you give a detailed explanation about the theory behind Centre of gravity / center of mass. But you don't mention how to change this in the AC files. In which file and whitch line can I change this?

Even though the manual is not finished, there should be all the parameters to configure the centre of gravity of the car.

You can't change it which should be the point of the theory? The center of mass is always at 0, you set everything else relative to that (graphics from car.ini, suspension from suspension.ini, and most other stuff follows the graphics offset)

Pardon my intrusion, but while it may be that way for AC, that is not true in terms of real world physics. As a counterexample, adding/removing fuel or ballast changes the position of your CoG in real time. When you try to explain something, you should refer to reality first, and only then show how it's interpreted in the simulator. I believe that's especially important when talking to newbies, because you may bias them the wrong way. Sorry Stereo, but I'll try to help nonetheless

To @Nitro McClean :
What Stereo means is that when you configure a car you need to determine the location of the real car's CoG, and the way AC works, that becomes your new reference point, a new XYZ-zero coordinate, so you can set all the other parameters along, referenced to it by distance.
Fixing the CoG in space first is a choice based upon a pretty rational principle: any body can be simplified with a point mass if you locate its CoG. And very often this eases calculations.
If you didn't consider the CoG as the reference, you could place the origin of the XYZ system reserved to physics anywhere on the car, but that would be quite difficult to keep track of.

Keep in mind that the origins of the physics and graphics reference systems are different (read "they work for entirely separate stuff") and can only be aligned to make the car 3D body match the physical backbone with the graphics offsets.
Parameters like BASEY and CG_LOCATION are useful to locate the suspensions properly, always referenced to the CoG previously set.
As a little warning: changing the location of the CoG "by feel" will not bring true solutions to your problems, in fact it will be just plain wrong. There are very specific formulas and measurement tools/machines which can determine the position of a vehicle's centre of gravity.

Anyway, these things are explained in the manual, so you just have to read what you did not. When I'll have time I'll check those parts once again, but I do remember that there were quite decent explanations, at least for these basics.
And I don't know which AC karts you're talking about, but I know for a fact that there are very good ones out there, made by people who know their stuff. They're probably here on RD, too, just search for them.

 

[Nitro McClean]

Even though the manual is not finished, there should be all the parameters to configure the centre of gravity of the car.

Pardon my intrusion, but while it may be that way for AC, that is not true in terms of real world physics. As a counterexample, adding/removing fuel or ballast changes the position of your CoG in real time. When you try to explain something, you should refer to reality first, and only then show how it's interpreted in the simulator. I believe that's especially important when talking to newbies, because you may bias them the wrong way. Sorry Stereo, but I'll try to help nonetheless

To @Nitro McClean :
What Stereo means is that when you configure a car you need to determine the location of the real car's CoG, and the way AC works, that becomes your new reference point, a new XYZ-zero coordinate, so you can set all the other parameters along, referenced to it by distance.
Fixing the CoG in space first is a choice based upon a pretty rational principle: any body can be simplified with a point mass if you locate its CoG. And very often this eases calculations.
If you didn't consider the CoG as the reference, you could place the origin of the XYZ system reserved to physics anywhere on the car, but that would be quite difficult to keep track of.

Keep in mind that the origins of the physics and graphics reference systems are different (read "they work for entirely separate stuff") and can only be aligned to make the car 3D body match the physical backbone with the graphics offsets.
Parameters like BASEY and CG_LOCATION are useful to locate the suspensions properly, always referenced to the CoG previously set.
As a little warning: changing the location of the CoG "by feel" will not bring true solutions to your problems, in fact it will be just plain wrong. There are very specific formulas and measurement tools/machines which can determine the position of a vehicle's centre of gravity.

Anyway, these things are explained in the manual, so you just have to read what you did not. When I'll have time I'll check those parts once again, but I do remember that there were quite decent explanations, at least for these basics.
And I don't know which AC karts you're talking about, but I know for a fact that there are very good ones out there, made by people who know their stuff. They're probably here on RD, too, just search for them.

View attachment 769171

Even though the manual is not finished, there should be all the parameters to configure the centre of gravity of the car.

Pardon my intrusion, but while it may be that way for AC, that is not true in terms of real world physics. As a counterexample, adding/removing fuel or ballast changes the position of your CoG in real time. When you try to explain something, you should refer to reality first, and only then show how it's interpreted in the simulator. I believe that's especially important when talking to newbies, because you may bias them the wrong way. Sorry Stereo, but I'll try to help nonetheless

To @Nitro McClean :
What Stereo means is that when you configure a car you need to determine the location of the real car's CoG, and the way AC works, that becomes your new reference point, a new XYZ-zero coordinate, so you can set all the other parameters along, referenced to it by distance.
Fixing the CoG in space first is a choice based upon a pretty rational principle: any body can be simplified with a point mass if you locate its CoG. And very often this eases calculations.
If you didn't consider the CoG as the reference, you could place the origin of the XYZ system reserved to physics anywhere on the car, but that would be quite difficult to keep track of.

Keep in mind that the origins of the physics and graphics reference systems are different (read "they work for entirely separate stuff") and can only be aligned to make the car 3D body match the physical backbone with the graphics offsets.
Parameters like BASEY and CG_LOCATION are useful to locate the suspensions properly, always referenced to the CoG previously set.
As a little warning: changing the location of the CoG "by feel" will not bring true solutions to your problems, in fact it will be just plain wrong. There are very specific formulas and measurement tools/machines which can determine the position of a vehicle's centre of gravity.

Anyway, these things are explained in the manual, so you just have to read what you did not. When I'll have time I'll check those parts once again, but I do remember that there were quite decent explanations, at least for these basics.
And I don't know which AC karts you're talking about, but I know for a fact that there are very good ones out there, made by people who know their stuff. They're probably here on RD, too, just search for them.

View attachment 769171

What

Even though the manual is not finished, there should be all the parameters to configure the centre of gravity of the car.

Pardon my intrusion, but while it may be that way for AC, that is not true in terms of real world physics. As a counterexample, adding/removing fuel or ballast changes the position of your CoG in real time. When you try to explain something, you should refer to reality first, and only then show how it's interpreted in the simulator. I believe that's especially important when talking to newbies, because you may bias them the wrong way. Sorry Stereo, but I'll try to help nonetheless

To @Nitro McClean :
What Stereo means is that when you configure a car you need to determine the location of the real car's CoG, and the way AC works, that becomes your new reference point, a new XYZ-zero coordinate, so you can set all the other parameters along, referenced to it by distance.
Fixing the CoG in space first is a choice based upon a pretty rational principle: any body can be simplified with a point mass if you locate its CoG. And very often this eases calculations.
If you didn't consider the CoG as the reference, you could place the origin of the XYZ system reserved to physics anywhere on the car, but that would be quite difficult to keep track of.

Keep in mind that the origins of the physics and graphics reference systems are different (read "they work for entirely separate stuff") and can only be aligned to make the car 3D body match the physical backbone with the graphics offsets.
Parameters like BASEY and CG_LOCATION are useful to locate the suspensions properly, always referenced to the CoG previously set.
As a little warning: changing the location of the CoG "by feel" will not bring true solutions to your problems, in fact it will be just plain wrong. There are very specific formulas and measurement tools/machines which can determine the position of a vehicle's centre of gravity.

Anyway, these things are explained in the manual, so you just have to read what you did not. When I'll have time I'll check those parts once again, but I do remember that there were quite decent explanations, at least for these basics.
And I don't know which AC karts you're talking about, but I know for a fact that there are very good ones out there, made by people who know their stuff. They're probably here on RD, too, just search for them.

View attachment 769171

Why do you think I didn't read this part of the manual completely? because I have read it completely. Even if you write another 200 pages explaining the theory of the center of gravity, that does not change the fact that in rFactor the center of gravity can easily be adjusted afterwards and in AC it is very cumbersome. I have tried all the karts on Overtake (/Race Department) and they all have the same problem. They all don't drive like a real kart drives. The challenge for a simulator is that a kart in combination with the driver does not have a fixed center of gravity, but a moving one. The driver leans outwards in the bend, causing the rear wheel to come off the ground on the inside of the bend. As a result, the kart actually goes through the bend on three wheels and the understeer disappears. This is not simulated in rFactor nor in Assetto Corsa. I spent a number of years adjusting the physics of karts in rFactor for drivers who used rFactor to prepare for their real-life races. Based on their feedback, I made adjustments to make the kart in the simulator as similar as possible to the real thing. When I first made the center of gravity adjustment, I didn't tell anyone and asked drivers if they wanted to try out a new version. They were completely surprised. Their response was "how can it feel so real". They didn't understand it. Until the moment that I showed from behind the kart in the replay what happens when they drive through a bend. That explained everything to them. I think it's a shame that I haven't yet managed to do this in Assetto Corsa.

 

[Stereo]

It's really not cumbersome, it's just not obvious how to do it because, while AC is moddable, this is stuff that was designed to be used by devs, who know what everything does, and when inputting car data, they just calculate the correct value and set it to that, there's no "try 1cm higher or lower" process needed for CoG. Aside from that, it eliminates a variable, which means fewer ways the game can behave unexpectedly.

For vertical changes you edit BASEY in suspensions.ini (one each for front/rear), lower values (more negative) means higher CoG and GRAPHICS_OFFSET in car.ini, the Y value, again lower values for higher CoG.

I should also advise that there is a CSP feature to let the driver shift mass when steering (created for kart mods) but as far as I know the ones that use it assume the driver leans inward on corners. It's not something I've used so I can't give particulars, I just know it's out there.

 

[Nitro McClean]

It's really not cumbersome, it's just not obvious how to do it because, while AC is moddable, this is stuff that was designed to be used by devs, who know what everything does, and when inputting car data, they just calculate the correct value and set it to that, there's no "try 1cm higher or lower" process needed for CoG. Aside from that, it eliminates a variable, which means fewer ways the game can behave unexpectedly.

For vertical changes you edit BASEY in suspensions.ini (one each for front/rear), lower values (more negative) means higher CoG and GRAPHICS_OFFSET in car.ini, the Y value, again lower values for higher CoG.

I should also advise that there is a CSP feature to let the driver shift mass when steering (created for kart mods) but as far as I know the ones that use it assume the driver leans inward on corners. It's not something I've used so I can't give particulars, I just know it's out

 

[Nitro McClean]

Thank you very much for this answer. I will try to see if this also has the desired effect in Assetto Corsa.

 

[GzeroD]

The driver doesn't necessarily need to lean outwards to turn a Kart as the Caster will lift the inside rear wheel. I guess you lean in or out to adjust how much weight is carried by the outside front wheel as the same caster lifts it off the ground.
The ONLY Karts to do this are mine and ACKarting (search Patreon). Mine worked before COSMIC, and ACK use COSMIC, and mine are currently being converted to COSMIC which does a 'real' job rather then the 'hack' I used.

 

[Nitro McClean]

The driver doesn't necessarily need to lean outwards to turn a Kart as the Caster will lift the inside rear wheel. I guess you lean in or out to adjust how much weight is carried by the outside front wheel as the same caster lifts it off the ground.
The ONLY Karts to do this are mine and ACKarting (search Patreon). Mine worked before COSMIC, and ACK use COSMIC, and mine are currently being converted to COSMIC which does a 'real' job rather then the 'hack' I used.

I don't quite understand what you mean. Every kart driver I've talked to about this subject has explained to me that a driver is moving his body outward in a turn to get the inside rear wheel off the ground. The construction of the suspension and steering of the front wheels are made in such a way that in a bend the kart tends to move the rear wheel off the ground on the inside of the bend, but the driver's weight is really needed to do this. to make it happen. The adjustment of the front wheels can make it easier or more difficult, depending on the driving style of the driver.

 

[Stereo]

Mine worked before COSMIC, and ACK use COSMIC, and mine are currently being converted to COSMIC which does a 'real' job rather then the 'hack' I used.

Yeah, it's not strictly necessary, just gets rid of workarounds for eliminating springrates so you run a much simpler (and probably more stable) platform.

 

[brotto marco]

Why do you think I didn't read this part of the manual completely?

Because at page 433 you have the explanation of all the parameters you need to configure the CoG. It's not that difficult to find, nor that long to read (about half a page).

Their response was "how can it feel so real"

From an engineering standpoint, driver feedback has limited reliability and undefined accuracy most of the time. It cannot be considered data unless associated to circumstances of repeatability, with controlled test conditions.
An engineer should acknowledge the opinion, but then it has to be approved/denied with scientific methods and good modeling of the problem, and that represents a cost. I can tolerate it here because you're trying to implement a behaviour that is not really modeled in AC. However you can tell me anything you want, opinions alone are not data. If you have graphs, numbers, etc., then that's something one can work with, otherwise it's like a blank slate.
For example you could record telemetry runs with stock karts and your modified versions and compare the lat/long accelerations when cornering. Then you could check your results with something like this:

That would be better than nothing.

 

[GzeroD]

I don't quite understand what you mean. Every kart driver I've talked to about this subject has explained to me that a driver is moving his body outward in a turn to get the inside rear wheel off the ground. The construction of the suspension and steering of the front wheels are made in such a way that in a bend the kart tends to move the rear wheel off the ground on the inside of the bend, but the driver's weight is really needed to do this. to make it happen. The adjustment of the front wheels can make it easier or more difficult, depending on the driving style of the driver.

Necessary as in it 'is' not what makes the Kart turn. You can build a Kart where you don't need to lean, see SuperKarts, but a Kart without Caster leads to terminal understeer.
A little pedantic, maybe, as everything you say above is correct, as having set up a Kart to have enough rear weight bias to get good traction, you would then need to move the CoG, that is lean, to bring enough weight to bear on the outside front and have the Kart three wheel. And yes in a game where leaning is not possible, then a compromise of having the CoG higher than reality will trade a little fore/aft instability, which is not so bad as a Kart has no suspension, for a better lateral weight transfer.