Perhaps Doug (Milliken) can comment on the data shown in figure 12 of the previously cited Kasprzak paper, which he co-authored. From that paper: "[f]igure 12 presents plots of lateral force vs. slip angle at 5 different loads and 4 different pressures. This raw data was gathered through measurement on a tire testing machine."
http://i16.tinypic.com/4r7vmyq.jpg
To emphasize the point: this is real measured data. The data shows significant drop off after peak over a range of load and pressure combinations. There is no explicit mention that truck tyres were used (though passenger cars are mentioned twice) nor is there any explicit mention that measurements were made in wet conditions. It is therefore natural to assume that the data was measured in normal dry conditions and is from normal passenger car tyres. Was the data obtained from truck tyres and/or in wet conditions without that being mentioned in the paper? I have emailed Dr Kasprzak asking him how that data was obtained, under what conditions and for details about the tyre(s) used.
Similar graphs showing significant drop off after the peak in measured data occur in Milliken and Milliken; see, for example, Figure 14.1 (which was obtained from a P195/70R14 tyre; the P indicates that it's a passenger car tyre). Was this raw data also obtained in wet conditions for some reason? Perhaps Doug can clarify that point also?
In the GTR2 curves I've looked at even at high slip angles the drop off from peak is only a few percent e.g. the curve is still at 93% of peak even at a 45° slip angle. Further, the fact that the curves extend out to extremely high slip angles (120° max) has nothing to do with their accuracy or inaccuracy throughout the range of slip angles normally encountered in-game and to characterize them by their behaviour at their extreme limits is misleading.
And I'm not trying to defend them. I don't like the way the cars feel or behave in rFactor/GTR2/etc - with a couple of notable recent exceptions in rFactor.
Ask Pacejka. Better still, ask your colleagues Kasprzak, Milliken, Radt et al why their normalized slip angle vs lateral force curves show a drop below 90% of peak even at low slip angles as shown in this graph from the paper you cited earlier: http://i8.tinypic.com/6frvejn.jpg. Here's the link to the paper again: http://does.eng.buffalo.edu/pu ... ons/Kasprzak.SAE.2006.pdf. The issue is also discussed by Radt in some detail in chapter 14 of Milliken and Milliken and includes similar curves that also display significant drop offs below peak even at low slip angles.
I don't see how you can on the one hand criticize the slip curves in rFactor/GTR2/etc as being nonsensical for showing drop off yet on the other hand point to research which shows slip curves with similar drop offs without criticizing it too.
Here's a screengrab of the GTR2 Michelin M3 GTR tyre file in Dave Purdy's Physics Editor. http://i17.tinypic.com/5ybsgh3.jpg The y-axis is lateral force (normalized to a peak value of 1.0), the x-axis is slip angle (measured in steps where each step is 0.009 radians). The max value along the x-axis is 236 steps which corresponds to 2.124 radians or 121.7°. The peak normalized lateral force occurs at step 11 which corresponds to a slip angle of 0.099 radians or 5.7°. At a slip angle of 45° (0.785 radians, step 87) the normalized lateral force is 92.8% of the peak.
So, while the curves do drop off to 60-70% of peak this only happens at extremely high slip angles that likely will not occur in-game. For the range of slip angles that are likely to occur, the curves remain in the 90+% range throughout.
I'm not arguing for the accuracy of the tyres in ISI-based sims, by the way. They largely feel strange to me too.
Incidentally, for a bit of fun I tried using Niels' C6 Corvette tyre files with the M3 GTR in GTR2. It was sliding all over the track - lots of fun!
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To be fair though Todd, the GTR2 tyre file slip angle vs lateral force curves go out to 120° or so. At a more reasonable high slip angle, say 45°, the lateral force is still around 93% of peak.
Also, I don't think it's clear how the curves in the tyre files are actually used by the ISI physics engine(s). There are a handful of modifiers that are used to scale, shift and transform the curves as a function of load, pressure, temperature, etc. At the end of the day, the initial curves might not be particularly meaningful. For example, as a test, I tried setting one of the slip angle vs lateral force curves to a flat line at 1.00, leaving the other tyre parameters the same; the in-game results were not significantly different than using the original unmodified tyre file. I think parameters like LatPeak, LoadSens, DryLatLong and DropoffFunction are much more important in determining the actual values used by the game than the raw data in the curve table itself.
Then again, what do I know? The ISI tyre files are a mystery.
As much as I like the Virtua LM Le Mans track, I wish they hadn't added artificial vibration effects to model undulations in the track surface along the straights. I understand that modeling the entire track surface in sufficient detail to capture subtle undulations would have been an enormous undertaking but the artificial effects mess up the RealFeel force feedback, in my opinion. Thankfully, they can be adjusted in the TDF file.
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Update: resolved my notchy force feedback by adjusting the MaxForceAtSteeringRack value in RealFeelPlugin.ini from the usual setting that I use of -1000.0 to -1850.0. I know that the C6 readme suggests using a much higher (well, lower when you take the -ve sign into account) setting than that but higher (lower) settings tend to smooth out the force feedback too much for my taste.
Just gave it a shakedown at my new favourite test track, Varano. Excellent job!
My only slight niggle is that the force feedback feels a bit notchy around the centre. It's got nothing to do with reversed feedback effects or anything like that. It feels as though it has something to do with self-aligning torque or the hysteresis of the tyres, particularly at low slip angles. Interestingly, when I tried substituting the V8Factor TBC tyre file in place of the C6_tires TBC as a test, the notchiness was much less pronounced, so it's related to the tyres in some way. It's only a minor niggle, really, as the rest of the package is superb.
The Corvette joins the very small stable of cars (present count: 3) that I can actually stand to drive in rFactor. Well done!
My only slight niggle is that the force feedback feels a bit notchy around the centre. It's got nothing to do with reversed feedback effects or anything like that. It feels as though it has something to do with self-aligning torque or the hysteresis of the tyres, particularly at low slip angles. Interestingly, when I tried substituting the V8Factor TBC tyre file in place of the C6_tires TBC as a test, the notchiness was much less pronounced, so it's related to the tyres in some way. It's only a minor niggle, really, as the rest of the package is superb.
The Corvette joins the very small stable of cars (present count: 3) that I can actually stand to drive in rFactor. Well done!
I've been enjoying the hell out of the new Caterham mod for rFactor which takes advantage of the new carFactory suspension design tool. Together with the realFeel plug-in which generates force feedback from the underlying physics instead of relying on event driven effects, it's a real eye-opener. Finally, almost two years after it was released, a car in rFactor actually feels like a car! The disconnected floating feeling is gone, the suspension actually works and the car's dynamic behaviour feels intuitively right.
I almost hate to say it -- and I'm as surprised as anyone that I could think this way about a car in rFactor -- but in my opinion a carFactory designed Caterham with the realFeel plug-in on a well-designed track add-on like Varano or Goldenport offers an even better driving experience than LFS right now. There are a lot of caveats -- the realFeel plug-in highlights how poorly made the bulk of current rFactor car and track add-ons are and LFS still offers a better overall racing experience -- but the bar has been raised.
I look forward to trying your Corvette when it's released, Niels, and hope that it manages to raise the standard even higher.
I almost hate to say it -- and I'm as surprised as anyone that I could think this way about a car in rFactor -- but in my opinion a carFactory designed Caterham with the realFeel plug-in on a well-designed track add-on like Varano or Goldenport offers an even better driving experience than LFS right now. There are a lot of caveats -- the realFeel plug-in highlights how poorly made the bulk of current rFactor car and track add-ons are and LFS still offers a better overall racing experience -- but the bar has been raised.
I look forward to trying your Corvette when it's released, Niels, and hope that it manages to raise the standard even higher.
Here's a copy of the graph charting yaw angle against coefficient of lift for various rear spoiler configurations that Todd and BBT are talking about.
http://i9.tinypic.com/4pvajhg.jpg
In the third config, the lift coeff rises very slightly at small yaw angles.
As Todd mentioned, this graph is taken from 'Race Car Vehicle Dynamics' by Milliken and Milliken, pp 494.
http://i9.tinypic.com/4pvajhg.jpg
In the third config, the lift coeff rises very slightly at small yaw angles.
As Todd mentioned, this graph is taken from 'Race Car Vehicle Dynamics' by Milliken and Milliken, pp 494.
Some series such as FIA GT, Le Mans and DTM allow the use of pneumatic jacks like you describe. Perhaps you're thinking of one of them?
It depends on the race. DTM has had some of the best racing I've ever seen yet sometimes it can be an F1 style procession from green light to chequered flag.
The track can make a big difference too. For example, the otherwise excellent Virtua_LM Le Mans seems to have issues with the track surface which cause force feedback oscillations even when using cars that otherwise work well with the RealFeel plug-in such as Major Parts/Cubits' Caterham mod.
I was experiencing something similar where I was locking up under braking much more easily after installing several of the Wxx test patches. A quick poke around in the controller setup screen showed that my controller axes needed to be recalibrated. Give that a try.
That video features Brian Beckman who is perhaps best known in sim racing circles for his 'Physics of Racing' series of papers. He's a professional physicist and amateur autocrosser. He holds a PhD in Astrophysics from Princeton University, has served as a Senior Engineer and Section Manager at the Jet Propulsion Labratory and is currently a Senior Software Architect at Microsoft. His credentials and experience are practically impeccable.
Hmm, I'm curious. Is the USB report queue also an issue when using DirectInput?
DirectInput allows an application to specify the polling rate for a device and also supplies device state data in either buffered or immediate mode. In immediate mode, the device state at the time the device is polled is returned and other device events are discarded. In buffered mode, device states are stored in a buffer until the application retrieves them.
Is the USB report queue overlaid on top of this? i.e. when a device is polled in immediate mode, is the first entry in the report queue returned or is the actual device state at the time the device is polled returned?
DirectInput allows an application to specify the polling rate for a device and also supplies device state data in either buffered or immediate mode. In immediate mode, the device state at the time the device is polled is returned and other device events are discarded. In buffered mode, device states are stored in a buffer until the application retrieves them.
Is the USB report queue overlaid on top of this? i.e. when a device is polled in immediate mode, is the first entry in the report queue returned or is the actual device state at the time the device is polled returned?
Although I have a CTRA silver license, I know that my racing skills and my lack of experience with the silver cars and tracks isn't up to the pro standard expected on the silver servers. As such, I won't join them until I feel able to be relatively competitive. Perhaps it's too easy to get a silver license at the moment?
Thanks Scawen, the AI reset deadlock fix works like a charm. The way the AI attempts to maneuver away from multi-car pile-ups is much more believable now. I even saw one do a three-point turn to get out of a particularly tangled jumble of cars. Nice!
Did you Alt-Tab out of LFS and then Alt-Tab back in? I sometimes get corrupted mirror textures when I do that.
Nice video, thanks for the link. The Lotus driver's website is mentioned at the end of the video (http://www.helise.net) and contains a large number of similar onboard videos from his track days with the car. http://www.helise.net/video.htm Lots of good stuff.
Scawen, in the W25 test thread, you asked if I could provide an SPR and a screenshot showing the AI reset deadlock issue I had mentioned. If you still want them, they're in the attached zip archive. The archive also contains a readme describing what to look for in the replay. If you need additional information, just ask.
A problem with the AI and car reset rules: if two or more AI crash in close proximity to one another (e.g. they crashed into one another) and need to reset, they can't. Car A can't reset because car B is nearby and vice versa. The result is that they get stuck in an endless cycle where each prevents the other from resetting and they remain stuck where they are for the duration of the session. Some of the tight corners in South City can end up being a veritable wreckers yard as more and more AI crash into their immobilized brethren on each successive lap.
This is what seems to have caused the stream of 'Can't reset' warning messages mentioned in a previous post.
This is what seems to have caused the stream of 'Can't reset' warning messages mentioned in a previous post.
In single player when running AI, if the AI crashes and attempts a repair, the warning messages 'Can't reset - would cause a yellow flag' and/or 'Can't reset - could hit another car' are sometimes displayed repeatedly, as shown in the attached screengrab. Several of these messages seem to be displayed for each 'AI repair' and the messages are sometimes displayed over and over again, lap after lap even if there are no new 'AI repair' messages. It can be very distracting.
TrackIR 6DOF: excellent, I have been waiting for this for a long time! The subtle movements of the eyepoint as you lean into a corner or shift in your seat as you look around really help to bring the game alive. Nice work and thank you Scawen.
Emotional? If by emotional you mean passionate then, sure, passion is important. Passion sustains the commitment and attention to detail that is needed to fashion any creative piece to a high standard, be it artwork, music, prose, even programming. And I can't think of a quicker way to kill that passion than to expose yourself to the petty squabbling, angst and sometimes outright hostility found in user-community forums such as this one.
That's unnecessarily harsh. I certainly don't feel that Eric is flipping anyone the bird nor do I feel that his decision to not to interact with the 'community' (how I hate that word) shows any disdain. Frankly, if I were on the development team, I would maintain as much distance from the forums and user-base as possible too; it must be an enormous mental and emotional drain having to deal with all the pettiness that goes on in the 'community'.
FGED GREDG RDFGDR GSFDG