Racer v0.8.25 released!

[Ruud]

Another one, esp important with the tangents problems (white spots/dark triangles):

Get it at http://www.racer.nl/download/racer0.8.25.zip

Changes:
- Setting racer.ini's textures.compression to 0 had an effect on visuals (no SRGB).
- Ctrl-1 now shows when the force feedback is saturating the wheel (>20 Nm).
- Controller setup screen now removed POV and added horn and wiper controls.
- 'sunny' default was 0, should have been 1.
- standard_bump_f.cg now takes specularity from the normalmap's alpha channel (2nd layer)
- Only 3/4 of the tangents was passed for each objects. White spots and black triangles.
- Baja shader bug fixed (dyn_standard_bump_speca.cg was used)
- ff_damping (in car.ini) was applied to the wrong FF setting (friction instead of damping)
- Small change in spline triangle checking for road surfaces; in Carlswood doing Shift-F
4 times failed to recognize the underlying spline triangle.
- Y offset in viewelt_f.cg removed; dials were slightly moved up a centimeter.
- Using Cg 3.0 toolkit (was 2.2) from July 2010.
- smCor for the 3rd shadow split slightly increased
- Only angular 3D view elements (dials) were painted correctly. Other texts could appear rotated.
- 'show splines' and all debug lines & points were rendered in HDR mode thus dark. Now drawn in LDR
after postprocessing to remain visible at all times.
- Live track envmapping anti-aliased the whole main FBO on each side update (ouch). Faster now
when setting render_once to 0.
- Mirror was anti-aliased twice. Slightly faster now.
- Exposure gradient changed from 0.5 to 0.35 (darker exposures)
- Music & background image handling in all setup screens now supported.
- More live track options in the graphics setup screen.
- Added bestline_v/f.cg for visible rendering of the 'best line' (F3 to toggle bestline)
- Added bestline.tga in data/images as an overlay image (uses alpha channel).
- 'sunny' included in sky shaders (GetSkyColorAtm) for the sun disc
- Undetected controllers would crash the controller setup screen in a few places.
- The lobby was painted incorrectly when using 3 monitors.
- Fixed stack underflow in car selection screen.

 

[DavidI]

Has anyone got reasonable pacejka suitable for large agricultural tires? Well actually tires for a monster truck. Same thing.

 

[Alex Forbin]

Has anyone got reasonable pacejka suitable for large agricultural tires? Well actually tires for a monster truck. Same thing.

Hehe I don't think they test those for anything other than their ability to hold air.
Seriously, I've never seen a test rig that could handle a tire that large, so I think you're going to have to wing it.

Alex Forbin

 

[Ruud]

I tried it. It completely changes the behavior. The car now sort of slides from one side of the road to the other. Not that realistic. But interesting.

I quickly added it to an existing car, to check with Pacejka.exe. The output image shows peak slipangle (lateral) force at high slip angles (20 degrees or more) which makes sense perhaps for motorcycles. Also note the Mz grows along with it. We've have trouble with that here with some of our cars (at Cruden) - the Mz peaking out at slip angle that are just too high. Which means the steering feeling will keep growing, never allowing you to feel when the peak lateral force (Fx) is crossed.
Still, with Pacejka Player you can often determine whether the tire makes sense. Mz peak should be around Fx peak. Fy (longitudinal) should peak around 0.2-0.6 SR roughly. But I haven't seen that many real tire curves.

@MrWhippy: MF5.2 is doing mainly what the older Pacejka (89-94 it seems) is doing. Better named coefficients and more subtle effects. The main thing where MF5.2 differs is combined slip; with the old Pacejka I'm doing the Brian Beckman/Gregor Veble tricks to cap forces to a friction circle. Completely mathematical idea. With MF5.2, those calculations are in the coefficients.
However, I believe that when skidding, MF5.2 probably also doesn't make any sense. Still, most of normal driving takes place near the limit, which is ok for Pacejka.
The tir file that is imported (to avoid having to copy/paste all the numbers; just about all the tire data I've seen comes as a .tir file) does NOT currently look at input limits though; max load, max slip angle and such. Clamping may be useful, but it will ofcourse flatten out the feeling when starting to lose control in the car.

 

[Ruud]

What car is it? The weight/dimensions/engine location will determine the polar moment. The wheel rates on most Racer cars are way too high, the suspension must move to work. Use the CG correction, it will be necessary to correct the camera/gauges/wipers, but it will be worth it from what I've seen. ARB values are another item that is usually set much too stiff in Racer, plus there is some debate as to how effective they are with the current tire model, so it's best to not go nuts on the values.
I hope this has helped some.

Probably a lot of people take spring rate as wheel rate, exaggerating the spring effect greatly. ARB values indeed seem to be abused quickly; hopefully the next half year I'll understand them better as for the amount you need to use. Perhaps around 40000 (which might be a lot still). We did find it hard recently to tune a car to under/oversteer using ARB, which was a bit suspicious. Physics will get more focus next year.

 

[Ruud]

Has anyone got reasonable pacejka suitable for large agricultural tires? Well actually tires for a monster truck. Same thing.

As Alex said, probably no such data around. Data is also scarce because it takes a lot of effort/money to do them. Best to tweak an existing slow tire; increase the max slip angle, the relaxation length. Use Pacejka player to check those things. Only a few of them adjust the stiffness (shape) of the curve, with which you can tweak the max peak slip angle.

 

[Mr Whippy]

As Alex said, probably no such data around. Data is also scarce because it takes a lot of effort/money to do them. Best to tweak an existing slow tire; increase the max slip angle, the relaxation length. Use Pacejka player to check those things. Only a few of them adjust the stiffness (shape) of the curve, with which you can tweak the max peak slip angle.

Relaxation length...

Hmmm... I'm starting to forget which ones we should use these days.

There is so much stuff in a car.ini that I'm not sure if we need any more, or has been superseded. Ie, optimum slip ratio/angle seem to only influence the skid sounds these days.

Would be cool to have a whole wheel/tyre/pacejka clarification guide for v0.9... so we only input what we actually need (I guess the debug can do this if we turn off falling back to default car.ini!?)



As for the MF5.2, so only the raw coefficients (simple name) in the TIR files are used, and all that manufacturer definition, tyre size, stiffness etc are not?



Alex, agricultural tyres should be fairly easy to get feeling ok. It depends what material you are wanting to make them for though. Asphalt or mud, or grass etc...
Main issue as we found out with big bouncy tyres in Racer is penetration depth limit!

Dave

 

[Cosmo°]

Has anyone got reasonable pacejka suitable for large agricultural tires? Well actually tires for a monster truck. Same thing.

You can have a look for the Hohenheim tyre model, it's been created specifically for agricultural applications. No ready-made pacejka sets available, but force/slip graphs and some numbers are out there.

 

[Stereo]

We did find it hard recently to tune a car to under/oversteer using ARB, which was a bit suspicious. Physics will get more focus next year.

Hmm, I didn't have trouble with that, but I was using exaggerated ARB values, to the point the car would lift up inside wheels cornering (eg. front k 3000, rear 9000 - it's a very soft tuned car). Getting the rear inside wheel unloaded is a good way to cause oversteer, even on a car with about 50hp.

 

[Ruud]

Relaxation length...

Hmmm... I'm starting to forget which ones we should use these days.

There is so much stuff in a car.ini that I'm not sure if we need any more, or has been superseded. Ie, optimum slip ratio/angle seem to only influence the skid sounds these days.

Would be cool to have a whole wheel/tyre/pacejka clarification guide for v0.9... so we only input what we actually need (I guess the debug can do this if we turn off falling back to default car.ini!?)


As for the MF5.2, so only the raw coefficients (simple name) in the TIR files are used, and all that manufacturer definition, tyre size, stiffness etc are not?

Tires are a combination of:
- Pacejka coefficients; from inputs slip angle, slip ratio, camber and load, you get outputs Fx/Fy/Mz (lon/lat/aligning moment)
- Relaxation length: influences speed of change of the Pacejka inputs, specifically slip angle and slip ratio. Camber and load are always instantaneous. Simulates slow flexing of the tire carcass (slow buildup of Fx/Fy/Mz).
- Optimum slip angle/ratio; used to determine amount of skidding. This also still influences combined slip (friction circle), but NOT in MF5.2 anymore, where Pacejka handles combined slip and the optimums are only used for sound.
- TIR files; only loads Pacejka coefficients currently. No tire size or stiffness (I presume you mean vertical stiffness; there's also lon & lat stiffness, but those are built into the Pacejka curves) or such.

Normally I'd calculate the optimal slip angle/ratio from the Pacejka curve directly, but some don't tend to get a real peak (Fy continues to rise) so they'd be a bit whacky sometimes. Also, for an F1 car, the average optimal slip angle is higher than when just assuming an F1 car standing still; you normally have some load and this might make it that the optimal slip angle is mostly higher (or lower) than if just dividing load into 4 (across each wheel).

 

[Raphael Buthmann]

I don't know why , but SQL Browser don't copy the values ,so I can't show here.
About the tire curve , you can search on this file.

http://www.4shared.com/file/mVc2dLEk/gamedb.html

So here is the forza database.
You need to install this program and open this database with this.
Take a look at the tire affect curve , and there are the values , something like a graph , but made in a table.

http://sourceforge.net/projects/sqlitebrowser/files/sqlitebrowser/2.0%20beta1/sqlitebrowser_200_b1_win.zip/download

 

[Alexander Knoll]

I don't know why , but SQL Browser don't copy the values ,so I can't show here.
About the tire curve , you can search on this file.

http://www.4shared.com/file/mVc2dLEk/gamedb.html

So here is the forza database.
You need to install this program and open this database with this.
Take a look at the tire affect curve , and there are the values , something like a graph , but made in a table.

http://sourceforge.net/projects/sqlitebrowser/files/sqlitebrowser/2.0 beta1/sqlitebrowser_200_b1_win.zip/download

FIX: http://sourceforge.net/projects/sql...0 beta1/sqlitebrowser_200_b1_win.zip/download

 

[Raphael Buthmann]

thanks *_*

 

[Mr Whippy]

Tires are a combination of:
- Pacejka coefficients; from inputs slip angle, slip ratio, camber and load, you get outputs Fx/Fy/Mz (lon/lat/aligning moment)
- Relaxation length: influences speed of change of the Pacejka inputs, specifically slip angle and slip ratio. Camber and load are always instantaneous. Simulates slow flexing of the tire carcass (slow buildup of Fx/Fy/Mz).
- Optimum slip angle/ratio; used to determine amount of skidding. This also still influences combined slip (friction circle), but NOT in MF5.2 anymore, where Pacejka handles combined slip and the optimums are only used for sound.
- TIR files; only loads Pacejka coefficients currently. No tire size or stiffness (I presume you mean vertical stiffness; there's also lon & lat stiffness, but those are built into the Pacejka curves) or such.

Normally I'd calculate the optimal slip angle/ratio from the Pacejka curve directly, but some don't tend to get a real peak (Fy continues to rise) so they'd be a bit whacky sometimes. Also, for an F1 car, the average optimal slip angle is higher than when just assuming an F1 car standing still; you normally have some load and this might make it that the optimal slip angle is mostly higher (or lower) than if just dividing load into 4 (across each wheel).

So relaxation length is like the tyre rate and tyre damping... ie, relax length does the x/z axis damping and springing, while tyre rate and damping do y axis because we need to see that in the tyre penetration of the driving surface and so on (ie, the deflection is important)


Dave

 

[Ruud]

So relaxation length is like the tyre rate and tyre damping... ie, relax length does the x/z axis damping and springing, while tyre rate and damping do y axis because we need to see that in the tyre penetration of the driving surface and so on (ie, the deflection is important)

It's a bit like that yes. Relaxation is more a filter based on spin distance of the tire, where tire damping is F=k*v, so velocity dependent. Note that .tir files indicate the vertical tire_damping (in one of those Adams examples, around 250).