There's actually two tests I'd do.
Start wheel moving right then switch to moving left and measure the
time taken until the change reaches the input. That's the total
latency.
Start it moving left again and measure the time until the signal
reaches the input. As the wheel had already been moving left it would
have taken up any slack in the mechanism. Subtract that from the
total latency figure and you have the slack in the wheel.
I'd also try it at different velocities to see if that affects the
latency.
I'm very interested to see what sort of figures you come up with.
I've been convinced for ages that the latency should be measured in
tenths rather then 10,000ths of a second.
Paul
:o)
> Dave - who do you program for?
> > I suppose I have a more direct comparison of the "MS" component in the
> > equation, because the Playstation2 can talk to the Logitech wheels via USB
> > and Logitech's custom API... our last PS2 game just used pretty much
> > identical code to our PC FF code (just tweaking the constant force
> > continuously based on force at the steering linkage); I started working on
> > my own hacked-together USB driver for other wheels, I'm curious to see
> what
> > kind of latency you can get sans Windows. Of course you still have to go
> > from the CPU to the IOP sub-processor to get to the USB via DMA, so it's
> not
> > as good as an ISA card or something.
Beers and cheers
(uncle) Goy
"The Pits" http://www.theuspits.com/
* Spam is for losers who can't get business any other way *
"Spamkiller" http://www.spamkiller.com
Instead of basing FF effects on steering mechanism forces, simply tie FF
to the lateral g-forces acting on the driver? Then you get the
seat-of-the-pants feel that is missing from a computer simulation.
F1-2001 does it this way, and for my money, it's the best feeling FF
currently available in a PC driving sim.
--
Pat Dotson
When you move aft along the wheelbase to the driver position, then the
onset of lateral force lags a bit, because the whole car has to rotate.
----------
Re original thread -- I'm looking forward to reading about some latency
measurements, could be very interesting. Might even be embarrasing for the
original authors of any bottleneck(s)!
-- Doug Milliken
>> Instead of basing FF effects on steering mechanism forces, simply tie FF
>> to the lateral g-forces acting on the driver? Then you get the
>> seat-of-the-pants feel that is missing from a computer simulation.
>If I understand what you are saying, I think this would add more lag.
...
Isn't the lateral acceleration on every part of the car the same?
(obviously the lateral velocity isn't, but the acceleration seems
untied to a position in the car).
That would suggest no more lag than usual, since even though
rotational *velocity* might need a buildup, the *acceleration* of the
car body doesn't (and that's where you derive the FF from).
Ruud van Gaal
Free car sim : http://www.marketgraph.nl/gallery/racer/
Pencil art : http://www.marketgraph.nl/gallery/
Ice D
> >> Instead of basing FF effects on steering mechanism forces, simply tie
FF
> >> to the lateral g-forces acting on the driver? Then you get the
> >> seat-of-the-pants feel that is missing from a computer simulation.
> >If I understand what you are saying, I think this would add more lag.
> Hm, does indeed look like it. I'll add an option to use this kind of
> FF (although it will need tweaking, as the influence of lateral
> acceleration vs. tire grip is probably mostly a matter of personal
> feel) in Racer.
> It's not that hard to build in, so that might give a nice testbed.
> ...
> >When you move aft along the wheelbase to the driver position, then the
> >onset of lateral force lags a bit, because the whole car has to rotate.
> Isn't the lateral acceleration on every part of the car the same?
> (obviously the lateral velocity isn't, but the acceleration seems
> untied to a position in the car).
> That would suggest no more lag than usual, since even though
> rotational *velocity* might need a buildup, the *acceleration* of the
> car body doesn't (and that's where you derive the FF from).
> Ruud van Gaal
> Free car sim : http://www.marketgraph.nl/gallery/racer/
> Pencil art : http://www.marketgraph.nl/gallery/
> My god, we are still talking about wheels that shake a bit as you drive,
> right? Never mind, carry on... ;)
> Ice D
> > >> Instead of basing FF effects on steering mechanism forces, simply tie
> FF
> > >> to the lateral g-forces acting on the driver? Then you get the
> > >> seat-of-the-pants feel that is missing from a computer simulation.
> > >If I understand what you are saying, I think this would add more lag.
> > Hm, does indeed look like it. I'll add an option to use this kind of
> > FF (although it will need tweaking, as the influence of lateral
> > acceleration vs. tire grip is probably mostly a matter of personal
> > feel) in Racer.
> > It's not that hard to build in, so that might give a nice testbed.
> > ...
> > >When you move aft along the wheelbase to the driver position, then the
> > >onset of lateral force lags a bit, because the whole car has to rotate.
> > Isn't the lateral acceleration on every part of the car the same?
> > (obviously the lateral velocity isn't, but the acceleration seems
> > untied to a position in the car).
> > That would suggest no more lag than usual, since even though
> > rotational *velocity* might need a buildup, the *acceleration* of the
> > car body doesn't (and that's where you derive the FF from).
> > Ruud van Gaal
> > Free car sim : http://www.marketgraph.nl/gallery/racer/
> > Pencil art : http://www.marketgraph.nl/gallery/
More interesting stuff, but confusing. The #1 complaint
I hear from people who *should* be interested in PC sims,
but arent' (people who race in real life) is that they
can't feel what the car is doing.
In my opinion, current FF comes pretty close to making up
for the SOP feel. But if real drivers don't necessarily
use the g-force feedback they get, then what should PC
sim FF be based upon? In my real experience, which is
95% go-kart, actual wheel feedback isn't much of a factor
in driving. Maybe it should be, but it generally isn't.
That's why I like the idea of lateral force-based FF.
--
Pat Dotson
Winston Cup, Sprint cars, F1, probably others. It's an area
ripe for innovation, imo.
Why off list??
-- Doug Milliken
Here is why:
The front wheels can still be gripping, and still be
generating lateral force, even when the back wheels
have lost traction and are sliding. It will take a
moment for the front wheels to also lose traction,
whether it's a slide, or a spin or whatever. It seems
like a mid-car position would give you a better idea
of what the whole car is really doing. This method
should give a better feel for when the car is getting
loose.
It would be great to be able to test this idea in RACER.
--
Pat Dotson
> >When you move aft along the wheelbase to the driver position, then
the
> >onset of lateral force lags a bit, because the whole car has to
rotate.
>
> Isn't the lateral acceleration on every part of the car the same?
> (obviously the lateral velocity isn't, but the acceleration seems
> untied to a position in the car).
> That would suggest no more lag than usual, since even though
> rotational *velocity* might need a buildup, the *acceleration* of the
> car body doesn't (and that's where you derive the FF from).
Ice D
> > My god, we are still talking about wheels that shake a bit as you drive,
> > right? Never mind, carry on... ;)
> > Ice D
> > > >> Instead of basing FF effects on steering mechanism forces, simply
tie
> > FF
> > > >> to the lateral g-forces acting on the driver? Then you get the
> > > >> seat-of-the-pants feel that is missing from a computer simulation.
Dave was lead programmer for MGI's Viper Racing and as loyalty seems to be a
feature of sim programmers he's probably still there
Tony Whitley
Lead programmer, mobile phones :-(
"Tony Whitley" <> Dave was lead programmer for MGI's Viper Racing and as
loyalty seems to be a
You are correct sir. Dave has been the guy who's pumped out the patches
for Nascar Heat and done quite a-bit of troubleshooting too. Thanks sir...
ps...any of you seen the mod community springing up around Heat? Really
taking off thanks to the patch additions Dave included.
dh
>Here is why:
>The front wheels can still be gripping, and still be
>generating lateral force, even when the back wheels
>have lost traction and are sliding.
Ruud van Gaal
Free car sim : http://www.marketgraph.nl/gallery/racer/
Pencil art : http://www.marketgraph.nl/gallery/
Look at the simple 2-dof equations--this is enough of a hint<grin>.