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Force Feedback Revisited


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#1 Lee200

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Posted Jan 24 2014 - 03:08 PM

Guys, I've lost the bubble on what settings to use for FFB.  I have a black Momo wheel (yes, I understand it's a piece of junk) and am confused on how the Logitech Profiler app interfaces with the FFB settings in the core.ini file.

I've got some decent core.ini file settings so am not concerned too much about those.

1.  What settings should I use in the Logitech Profiler app to allow GPL to give the best FFB?

2.  If I don't allow the Logitech Profiler to automatically start when I start the computer, does it have any effect at all?

TIA.

#2 John Woods

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Posted Jan 24 2014 - 06:08 PM

There is a Grand Prix Legends Profile for download at the Wingman site.
Otherwise, as I understand, when set to open Profiler on startup it will load the default profile.
Thinking there is some reason why it should be set to open on startup, but forgot.
At the lower left of the Profiler menu there are attributes dialogues for controller functions.
Mine are set to 50% Sensitivity, 0% Deadzone, and 100% Range, for steering, throttle, and brakes.
But, now using a DFGT, so maybe not the same for MOMO, (a great wheel, btw, :)).

Practically, JMO the best thing about the Profiler is programming buttons on the wheel to click "esc," "enter," and "Shift-R."

Edited by John Woods, Jan 24 2014 - 06:09 PM.


#3 Robert Fleurke

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Posted Jan 24 2014 - 07:29 PM

Lee,

I use currently the same wheel (with MSSWFF pedals though, prefer them compared to the Momo, MSSWFF wheel is broken). I use 100% sensitivity, 0% deadzone and 100% range to have maximum control, but to some it might be twitchy. If you don't use the profiler I think you will have throttle/brake on one axis, however, I use other pedals...not really sure what the effect would be on the wheel...

My core.ini has .001 latency, 9 damping and 675 max force. In the end it's a personal taste what you feel comfortable with. To me these settings give me the best feedback, and still maximum control (not too much force) and the best precision...

PS: the properties for the wheel I have not checked combined axis, set 100% strength FF, 0% spring, 0% damping, no centerspring. My profiler/OS is dutch so I might not have used the right terms/words...

Edited by Robert Fleurke, Jan 24 2014 - 07:38 PM.


#4 Bob Simpson

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Posted Jan 24 2014 - 07:42 PM

As far as I know, the Profiler provides different button mappings and forces for different simulations if you wish.

However if you use the same settings for all Sims and don't map various wheel buttons differently, it's not necessary.  The Control panel > Devices and Printers > Device > Game Controller settings location lets you set the generic settings and the Profiler doesn't need to be running for those to be in effect.

For GPL's core.ini to fully control the forces, I only use Game controllers to set the rotation and overall force (103%) for my G25.  Everything else is set to 0 or else it'll mask the forces generated in GPL.  But everyone settings are different.

Edited by Bob Simpson, Jan 24 2014 - 07:42 PM.


#5 Lee200

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Posted Jan 25 2014 - 07:06 AM

Thanks guys.  So apparently the Profiler isn't really necessary if you want GPL to totally control the FFB.  So there is no point to have it running in the background interfering with things.

My wheel's rotation is fixed so I can't adjust it anyway.

#6 John Woods

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Posted Jan 25 2014 - 09:01 AM

When  Profiler is turned off the buttons on my wheel don't work.
Have to have the buttons.
Is it not the case that if any "third-party" controller utility is set to "100%" that it will use 100% of the input signal?
With it off there seems to be no difference in driving experience, feel, control, feedback, etc...but maybe it is alittle more twitchy near center without sensitivity at 50%. Hard to tell atm.

Edited by John Woods, Jan 26 2014 - 07:50 AM.


#7 Cookie

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Posted Jan 25 2014 - 10:18 AM

The best FFB I get with brr's FFB2 patch!!!
I raced with the Momo a long time...

Latency and damping set to 0.0  and the force to 420.

Quote

brr's readme:

This patch is intended to improve the GPL force feedback in terms of minimizing latency and removing everything but the direct feedback of forces from the physics engine. Those who prefer the ffb to have damping, centering, and other forces not derived from the car physics will find this patch less useful.

For best results, use with the 60fps patch which already reduces ffb latency and improves ffb accuracy by updating the forces more frequently.

Removing all damping makes forces more harsh, but at the same time more accurate. Your wheel may react very violently, so under any circumstances don't ignore the advice given in this README. Trying the patch is completely your own choice, and the responsibility is yours as well. If it does not work for you, just use the original ffb.

Edited by Cookie, Jan 25 2014 - 10:25 AM.


#8 fastmule

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Posted Jan 25 2014 - 10:23 AM

Anyone using a Logitech G27 have any good profile settings?

#9 Lee200

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Posted Jan 25 2014 - 02:29 PM

Thanks all for your help.  I found that the wheel works fine without the Profiler.

Will try the FFB patch too.

#10 Claudio Pablo Navonne

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Posted Jan 26 2014 - 09:13 AM

This is my profile setting, I hope it could be useful for you.

Attached Files


Edited by Claudio Pablo Navonne, Jan 26 2014 - 09:14 AM.


#11 Lee200

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Posted Jan 26 2014 - 12:27 PM

Warning--major geek stuff follows:  :zzzzz:

As you know, I like to get into the physics of stuff, but have never done much investigation of GPL's FFB code.  Brr's patch looks interesting and I will definitely give it a go.

I've been doing some reading of how real world feedback from the tires to the steering wheel works and it's really pretty simple.  The gist is that when a tire is slipping (not pointing in the direction the tire is actually going), it produces a lateral force.  This force of course keeps the car from sliding off a corner, but it also causes a torque about the suspension's kingpin axis.  This torque gets fed back to the steering wheel where the driver can sense the force on the steering wheel in his hands.

The reason there is torque about the kingpin axis is that the tire's lateral force acts at a distance behind where the kingpin axis intersects the ground.  This distance is called trail and total trail is the sum of two components:

1.  Mechanical Trail--caused by the wheel's caster angle.  The more caster, the more mechanical trail there is.  Mechanical trail acts at the distance from where the kingpin axis intersects the ground to the point directly underneath the wheel's center/axle.  This distance is constant so the torque it causes is constant.

Another, less common, method of providing mechanical trail is to locate the wheel/tire behind the axle.  This is what trailing arm suspensions do.

2.  Pneumatic Trail--caused by the tire's lateral force point in the contact patch acting behind the tire's center/axle.  This distance is not constant and changes as the slip angle does.  Pneumatic trail begins at zero at zero slip angle and increases to a certain slip angle where it begins to decrease.  It may in fact go negative at very high slip angles.  The slip angle at which maximum pneumatic trail occurs is typically a couple of degrees prior to the slip angle at which maximum grip occurs.  So the driver can feel the steering wheel force decrease which gives a warning that he is approaching maximum grip.

GPL models these effects as we all know through its FFB code.  It uses a curve shape which pretty much follows what a typical pneumatic trail curve would have although there are some slight differences around the zero slip angle point.  It also has a "caster" setting which is applied to the curve.  This setting probably doesn't represent a real world caster angle and mechanical trail, but is merely a fudge factor to give each car a slightly different FFB effect.  I don't know if the "caster" setting is based on the real '67 F1 car's caster or not.

GPL's FFB curve has its maximum force occurring a few degrees prior the the maximum grip slip angle.  As a result, you should be able to feel when the steering wheel force goes light which means you are approaching the maximum grip slip angle just as real world drivers can do.

Of course, we also have the FFB damping and latency settings in the core.ini file.  I suspect these were needed because GPL is a computer simulation and were not based on any real world parameters.

#12 Bob Simpson

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Posted Jan 26 2014 - 12:38 PM

Very interesting stuff Lee.

#13 colepole

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Posted Jan 26 2014 - 01:05 PM

Cheers Lee , I always find your scrutiny very interesting and helpful , especially when you tell us what gpl is actually computing etc.

:secret2:

Regards Col

#14 John Woods

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Posted Jan 27 2014 - 09:27 AM

Lately been stumbling into interest in force feedback and brr's FFB2 patch, which prompted a review of the topic as found here in several threads.
One thing that struck me in particular is brr's note about removing Inertia from the gpl.exe. This is really something interesting as the behavior of a car's wheels and tires, I would think, is very dependent on a critical characteristic called "rotational inertia." With brr's patch, it seems this is eliminated from the physics model.
Also, Paul Thurston back on the RSC Forums noted latency refers to the time it takes for an effect at the tire patch to be felt at the steering wheel, which seems like something those with interest in authenticity and realistic modeling would like to have...that their Grand Prix Legends cars behave as close as possible to a real car. brr's patch eliminates latency, so...how realistic is that?

Just bringing this up, (after all these years, right?), because interest in the FFB2 patch is current and many seem to think its a great improvement and may use it without knowing entirely what it does and that using it is surely, (and I think brr will agree), unrealistic in that the time it takes to feel a real effect is zeroed out in Grand Prix Legends, whereas, in real cars the time-delay effect is certainly there...no doubt it takes some time, even if 125 milliseconds as Paul calculated, (iirc), for the suspension to react to changes at the tire patch, and with no inertia, what parts of any real effects are not being modeled?

Here's some quotes from some threads found during a recent forums search:

brr, "The damping (one configured in the core.ini) is a simple proportional controller, i.e. it subtracts a portion of the previous value of the force from the current one.

Ffb2 patch removes two other types of damping: averaging of forces over one frame (originally this gives a half-frame delayed, smoothed force), and a non-zero damping value communicated to the ffb wheel driver (this damping cannot depend on GPL physics in any way). Inertia is also removed (this is also a non-zero value sent to the ffb wheel driver)."

mcmirande, "I think some damping is necessary when accelerating and the rear end is starting to slide, and also when braking. At least I feel it helps me giving a better feedback with the car."

Ken, "I tried it but I wasn't sure. It certainly gives a very clear feeling that the fronts have lost grip but it didn't seem to have any transition. I could feel resistance on the wheel, then suddenly none and it was like there was no ffb at all until the grip came back. With old ffb the damping seems to give that feeling of some transition from grip to no grip. Just my opinion. Peteri's new patch certainly felt very immediate I have to say."

brr, (responding to Ken), "That sounds correct. If damping is preferred, the patch isn't too useful since it removes it entirely. The way damping is implemented, it will not give useful feedback about car behaviour which is why I prefer to get rid of it."

jgf, "I use an R440 and have had no stuttering in GPL, though experienced it strongly in GTR2 and GTL (changing the effects setting from full to high cured that).  I've been satisfied with my settings of latency=0, damping=250, force=200;  no wrist snapping forces but a good feel.  I tried the ffb patch, with its recommended settings and with a couple of days' tweaking, but I actually seemed to have less ffb with that and found no settings I was happy with."

From Wikipedia, "Inertia is the resistance of any physical object to any change in its state of motion (including a change in direction). In other words, it is the tendency of objects to keep moving in a straight line at constant linear velocity. The principle of inertia is one of the fundamental principles of classical physics that are used to describe the motion of objects and how they are affected by applied forces.
Another form of inertia is rotational inertia (→ moment of inertia), which refers to the fact that a rotating rigid body maintains its state of uniform rotational motion. Its angular momentum is unchanged, unless an external torque is applied; this is also called conservation of angular momentum. Rotational inertia depends on the object remaining structurally intact as a rigid body, and also has practical consequences; For example, a gyroscope uses the property that it resists any change in the axis of rotation."


So, how does not having any inertia effect physics-model calculations at the tire patch? Does it make them more realistic, or just easier to drive?

While many feel the FFB2 patch helps them, and brr's interest in improving everyone's Grand Prix Legends experience is without question appreciated, perhaps some among us are less than fully aware of the significance of removing from the gpl.exe components that surely would be part of any other model of real car behavior.

Damping is something else of course, in that as I understand it only has something to do with buffering spikes on a game controller. However, as brr notes in the FFB2 readme, zeroing out damping can lead to very violent effects.

Please understand brr is one of my Grand Prix Legends heroes and without question enthusiastic, humble, and sincere, so this is not a criticism or rant about how bad FFB2 is. Really its about helping people make an more informed choice about using it.

brr, "Those who prefer the ffb to have damping, centering, and other forces not derived from the car physics will find this patch less useful."

I agree with brr and hope he understands my interest as always is only, with respect, questions and guesses.

Edited by John Woods, Jan 27 2014 - 09:53 AM.


#15 Robert Fleurke

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Posted Jan 27 2014 - 11:01 AM

Interesting stuff Lee and John, thanks for sharing your opinions and knowledge :)

Lee, so you don't know/or can'find out if each chassis in GPL have a fixed unique positive caster angle, or each the same!?

Would have been nice to be able change caster as well in GPL...if I remember well in NR2003, setup guru Volker Hackmann came up with maximum negative caster angles (prolly unrealistic IRL racing), which made the car very fast in combination with the rest of his coil bind setups, but the FF was really weird. With more positive caster angle you get more force and stability, with negative it became instable, and the FF felt really weird...

Edited by Robert Fleurke, Jan 27 2014 - 11:05 AM.


#16 Lee200

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Posted Jan 27 2014 - 11:31 AM

Here is a copy of a PM that I sent to John about this FFB stuff.  John asked me to repost it here for everyone to see:

Although I don't know for sure,  I don't think that Brr's FFB patch has any effect on the car's physics at all.  It simply modifies how the FFB code works.  So the car itself is going to respond to inertia and momentum changes just the same with or without the patch.  Remember that the FFB code only applies to the front tires so the rear tires provide no feedback at all other than you visually sensing the rear end stepping out.

Now what you may feel in the steering wheel is different as that goes through the FFB code.

Petteri apparently tried to take out all time delays and dampening in the FFB code.  As you point out, the code dampens the FFB by applying an opposite force.  As you said, I assume the original code was programmed this way because of spikes in the physics.  So some dampening was probably necessary to prevent weird FFB forces.

Is damping still needed with today's faster cpus or better performing steering wheels?  I don't know.

I agree with you that real world cars must have some latency from when the tire produces a force and the steering wheel receives it.  How long this takes is unknown to me, but probably isn't very long.  The bushings in the steering system will certainly affect this, but as race cars typically use very inflexible bushings and there normally isn't a steering "shimmy" damper in the system, it's probably not very long.

Same goes for dampening.  In real life race cars without a shimmy dampener, dampening is probably zero.

I once experimented with different caster settings to see what effect they had.  Certainly as the caster setting was increased, FFB forces became heavier.  There was also a secondary effect.  If you get into a car and turn the steering wheel lock from one side to the other, you will notice that the nose of the car will rise to a maximum, then fall to a minimum at wheel center, then do the same on the opposite side.  Its a very slight effect; however, increasing the caster setting increases this effect.  So the "caster", as used by GPL, affects both FFB forces and the amount of nose change as you turn the wheel.  I don't know if this is merely a visual effect or also affects the physics.

Edited by Lee200, Jan 27 2014 - 11:51 AM.


#17 Lee200

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Posted Jan 27 2014 - 11:41 AM

View PostRobert Fleurke, on Jan 27 2014 - 11:01 AM, said:

Lee, so you don't know/or can'find out if each chassis in GPL have a fixed unique positive caster angle, or each the same!?

Would have been nice to be able change caster as well in GPL...if I remember well in NR2003, setup guru Volker Hackmann came up with maximum negative caster angles (prolly unrealistic IRL racing), which made the car very fast in combination with the rest of his coil bind setups, but the FF was really weird. With more positive caster angle you get more force and stability, with negative it became instable, and the FF felt really weird...

Robert, I don't know if the "caster" setting that each car has is the actual caster angle or perhaps even the mechanical trail distance.  The setting certainly affects the steering wheel force so that higher caster settings result in higher steering wheel forces.  That is consistent with the setting representing caster.

However, Nigel once said that the caster setting was simply a factor that was applied to FFB curve in order to give each car a different feel.  As the FFB curve appears to represent the pneumatic trail, not mechanical trail, then the setting really isn't caster then.

AFAIK, there is no other fixed caster setting in the code that would affect the physics or the FFB.

See my previous post on how the "caster" setting also affects the nose rise effect as the steering wheel is turned.

Yes, positive caster should make the car more stable and negative caster will make it unstable.

#18 John Woods

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Posted Jan 27 2014 - 12:02 PM

This all points out the incredible foresight of the Papy Team I think, to make so much effort back when FFB was just barely getting on.

#19 Robert Fleurke

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Posted Jan 27 2014 - 12:03 PM

Thanks Lee.

Edited by Robert Fleurke, Jan 28 2014 - 04:37 PM.


#20 John Woods

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Posted Jan 28 2014 - 09:45 AM

Thanks Lee, for your interest in our ignorance, (speaking for all us ignorians).
At least for once it seems I'm not entirely wrong.
Okay, so far...
Guessing mechanical trail is modeled because that's what raises and lowers the nose? Noticed this effect before and guess it is reduced, (along with trail effects), when ride height is raised as it seems more pronounced when car is lowered?
Have to assume pneumatic trail is modeled in physics because that's what, as I understand, predominately effects changes in tire patch/suspension dynamics during a turn, (compared to mechanical trail). Because it is a variable force that changes car dynamics when in motion, it is difficult to imagine its not modeled, (used), both in FFB and in physics. Also, pneumatic trail is variable with tire pressure and temp, another reason to suspect its modeled somehow in physics.
Maybe its that FFB pneumatic trail calculations are fed to the physics model, which is why they seem to be found in only one place.
And this now seems even more weird: Road and Track once did a road test of an F1 car, IIRC a Honda, that featured a line drawing of a sideview that clearly showed negative caster at the front and positive caster at the rear. I thought at the time it looked sort of wrong, somehow, and have been curious about it ever since.




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