rec.autos.simulators

GP3 and GPL physics

Gregor Vebl

GP3 and GPL physics

by Gregor Vebl » Wed, 24 May 2000 04:00:00


If you ever get the info from back then I would really love to read it
as I didn't participate in r.a.s back then yet. But one should also be
aware that between GP1 and GP2 there is a huge difference in the feel
and behaviour of the car.

It's fairly easy to see what is modelled in F1 2000 simply by checking
the .veh files which are pure ASCII. Just looking at the parameters
combined with some engineering knowledge will, based on the knowledge of
how GPL works according to the Papy team, convince you that the physics
model of F1 2000 models basically the same stuff as GPL.

Aerodynamics, for example, is modelled separately for both wings with
the location points of the overall force specified. Drag on the car is
modelled as well, with the point of the overall drag force specified as
well. So you can easily see a full Newtonian phyics model being applied.

The individual suspension parts are indeed not modelled, but they are
not modelled in GPL either (WSC and MotorSims sim will be the first sim
to do so I believe). In a modern F1 car that is even less important as
in GPL since the suspension movement is rather small and can be well
described with the linear response theory just as it is.

The engine torque is clearly specified as a function of RPM, and so is
the negative torque when the accelerator is off.

There is obviously a misunderstanding. There are huge differences
between the different chassis, but in modern F1 these are dominated by
aerodynamic differences, and to a smaller extent by suspension effects.
I jwanted to say that no sim developer can gain access to the exact
aerodynamical data for different cars; even some smaller teams would
probably like to have those for their own cars as well :). You can
indeed put the differences between different chassis into a sim. For F1
2000 you can just go into the .veh files and do so yourself if you wish
to do so, it's up to you. I just wanted to say that the differences that
the programmers or yourself can buld into the program will in no way
reflect the real differences since that knowledge is not available.
That's why you see mostly the same chassis used for all cars in modern
F1 sims.

-Gregor

Jesper Adolfsso

GP3 and GPL physics

by Jesper Adolfsso » Wed, 24 May 2000 04:00:00


> The individual suspension parts are indeed not modelled, but they are
> not modelled in GPL either (WSC and MotorSims sim will be the first sim
> to do so I believe). In a modern F1 car that is even less important as
> in GPL since the suspension movement is rather small and can be well
> described with the linear response theory just as it is.

What do you mean when you say that the individual suspension parts are
not modelled? Do you mean that they
don't take into account all inertial coupling effects between the
movement of the suspension and the body of the car? Surely they must
have some sort of generalized position and velocity of each individual
suspension part. Do you mean by "linear response theory" that each
suspension part can be modelled with a fairly simple linear differential
equation?

/Jesper

Gregor Vebl

GP3 and GPL physics

by Gregor Vebl » Wed, 24 May 2000 04:00:00



> > The individual suspension parts are indeed not modelled, but they are
> > not modelled in GPL either (WSC and MotorSims sim will be the first sim
> > to do so I believe). In a modern F1 car that is even less important as
> > in GPL since the suspension movement is rather small and can be well
> > described with the linear response theory just as it is.

> What do you mean when you say that the individual suspension parts are
> not modelled? Do you mean that they
> don't take into account all inertial coupling effects between the
> movement of the suspension and the body of the car? Surely they must
> have some sort of generalized position and velocity of each individual
> suspension part. Do you mean by "linear response theory" that each
> suspension part can be modelled with a fairly simple linear differential
> equation?

> /Jesper

With the individual suspension parts I refer to individual links that
connect the wheel to the body (wishbones etc.). They model the movement
of the wheel on a single line (close to vertical), with the camber, toe
and other changes due to the suspension movement being linear fuctions
of the position of the wheel on the movement line. That is what I mean
when I refer to linear response.

-Gregor

Jesper Adolfsso

GP3 and GPL physics

by Jesper Adolfsso » Wed, 24 May 2000 04:00:00


> With the individual suspension parts I refer to individual links that
> connect the wheel to the body (wishbones etc.). They model the movement
> of the wheel on a single line (close to vertical), with the camber, toe
> and other changes due to the suspension movement being linear fuctions
> of the position of the wheel on the movement line. That is what I mean
> when I refer to linear response.

> -Gregor

ok then I misunderstood your posting

I would say that this is a fairly accurate model of a suspension and I
wonder why the want to model each individual link? I wonder if the
individual suspension parts are so heavy and move so much that they have
noticeable influence on the motion?

Gregor Vebl

GP3 and GPL physics

by Gregor Vebl » Wed, 24 May 2000 04:00:00


> ok then I misunderstood your posting

> I would say that this is a fairly accurate model of a suspension and I
> wonder why the want to model each individual link? I wonder if the
> individual suspension parts are so heavy and move so much that they have
> noticeable influence on the motion?

Yes, I agree, it is fairly accurate. It is not the modelling of inertial
properties of individual links that needs to be taken into accound,
however. It is the fact that with large enough suspension movement the
linear picture becomes less valid and then the individial link lenghts
need to be taken into account to properly describe wheel motion. But in
modern F1 sims that level of detail might just be an overkill due to the
small suspension movements in the first place.

-Gregor

Graeme Nas

GP3 and GPL physics

by Graeme Nas » Wed, 24 May 2000 04:00:00

Better than that :-) I have exactly the same system, and with a full
field I get the maximum 36fps for a whole race once I'm past the first
couple of turns.

It's also cool to be able to catch a full long race on replay with no
performance drop :-)

--
Cheers!
Graeme Nash

Jo Helse

GP3 and GPL physics

by Jo Helse » Wed, 24 May 2000 04:00:00


<lots snipped>
....

I don't have the slightest idea whether you are right or wrong, but I'm really
amazed how well you seem to know the internals of GP2.

And all that by turning a few laps????

I mean... To me it seems that even with the code right in front of you, it would
still be rather difficult to find out what it really _does_    :-)

JoH

------- The best way to accelerate a Mac is 9.81 m/s2 --------
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