X-Motor Racing

[Eugene Cojocar]

Make sure that you installed patch at the location of version 1.14 when the game is closed.
I'm uploading the whole package so you could replace it.

 

[andy4trance]

Thanks. Problem solved.

 

[Eugene Cojocar]

I'm really glad to hear that.
It was an unusual problem.

 

[aolas]

A new racing sim, thats interesting ...... I will give a try.....

 

[Eugene Cojocar]

This setups reduces sliding of the car.
It has different tires for the front and rear wheels.
Some changes in gear rations.
Just download, unzip and copy race.phs file into the Doxster directory which is your_xmr_dir\Data\Cars\Doxster

 

[andy4trance]

hi,

I followed the instruction (with the addition that the file need the .phs extension). But smth is wrong the friction seems 0, the car just slides away..

Is there smth I missed?

 

[Eugene Cojocar]

Hi,

You should extract s2.phs from this ZIP archive (s2.zip).
The exact size of s2.phs is 1080226 bytes.
Then put it to Doxster directory.
Select s2.phs in the garage before race.

 

[Eugene Cojocar]

This setups reduces sliding of the car also.
Download, unzip and copy s2.phs file into the Viperi directory which is your_xmr_dir\Data\Cars\Viperi

 

[Eugene Cojocar]

Here's a release version 1.15.
http://www.xmotorracing.com/download.html

Changes are:
- Improved tire model
- Changes in sound code
- Added OpenAL support
- Changes in FF code
- Engine load changes
- Slip/Slip angle code changes

P.S. A full version update is ready.

 

[andy4trance]

Thanks Eugene,

In version 1.14 there was already a change in the feel of FF (became more alive) but also in the tire behaviour. I can't describe it, but there is smth, maybe more control in the slide.
It would be interesting to have a description of the updates, not necessarily how did you do it but why and what is the outcome.
Thanks.

 

[Eugene Cojocar]

I think I could make this kind of description.
Maybe in blog here.

 

[andy4trance]

Great! Thanks.

 

[Eugene Cojocar]

Not at all.
Just my English level must be improved

 

[Eugene Cojocar]

I’m going to post here something info about vehicle dynamics so anyone could read and understand to tweak vehicle physics and understand updates. Maybe I will compile these posts and make online manual or something like this.
I begin with tires.
When a vehicle drives it contact with a road by tires so tires is the most important thing. It’s logically start from tires and some theory.

At the picture below you can see Tire Axis System that XMR uses.

You can compare it with SAE Axis that is attached.

A vehicle accelerates and brakes because of applied longitudinal tire force (Z axis).
If Z > 0 then tire accelerate a vehicle. If Z < 0 then tire brakes a vehicle.
A vehicle turns because of applied Lateral tire force (X axis).
If X > 0 then tire turns a vehicle to the right, else if X < 0 then tire turns a vehicle to the left.
A tire provides longitudinal and lateral forces if Normal force > 0. If Normal force is equal 0 then X and Z must be 0 also.


You can see tire forces on this video.

 

[Eugene Cojocar]

Longitudinal and lateral forces depend on slip ratio (slip) and slip angle. Camber thrust adds lateral force if camber angle is not zero.
Longitudinal force depends on slip ratio. XMR uses Sakai slip definition:

Traction Slip = V * cos (A) / w*R – 1
Braking Slip = 1 – (w*R)/(V*cos(A))


V – speed of the tire over the roadway
A – slip angle of the tire.
w – angular velocity of the tire
R – effective radius of the tire

Slip angle is an angle between a rolling tire’s direction and the direction of the tire heading.
You can see that Traction Slip < 0 and Braking Slip > 0.
Slip is limited by [-1..1]
For example, traction slip is -0.5 when the tire spinning (2X free rolling).
-1 Slip when tire spinning (infinite).
At this picture you can see a typical longitudinal forces (tractive or braking) diagram when a slip angle is zero and tire load is equal to 4 kN.

You can see when the tire has the maximum tractive and braking forces. Tractive force at -1 Slip is less than Tractive force at -0.5 Slip. The same behavior for braking forces.

On the picture below you can see a typical lateral force diagram when a slip is zero and tire load is equal to 4 kN.

You can see that lateral force is max at 7 degree of the slip angle. Lateral force is decreasing with the increasing of the slip angle. So you will have less grip at large slip angle.

And a short video to see slip and slip angle

 

[felipeshaman]

I'm having this problem with 3ds 2009

 

[Eugene Cojocar]

I'm having this problem with 3ds 2009

We'll try to test it for 3D Max 2009.
The export plug-in was developed for 3D Max 7.

Upd:
Here's export plugin for 3ds max 2009
x32 version
x64 version

 

[Eugene Cojocar]

Here's a release version 1.2.
http://www.xmotorracing.com/download.html

Changes are:
- Improved tire model
- Added one track (Monza)
- Advanced Tire Model Telemetry
- Changes in FF code
- Changes in clutch code
- Changes in engine code
- Improved mouse steering
- Improved precision of tire model in VehiclePhysics
- Improved graphics

Here's a lap of Monza:

 

[Eugene Cojocar]

Here's a release version 1.2.
http://www.xmotorracing.com/download.html

Changes are:
- Improved tire model
- Added one track (Monza)
- Advanced Tire Model Telemetry
- Changes in FF code
- Changes in clutch code
- Changes in engine code
- Improved mouse steering
- Improved precision of tire model in VehiclePhysics
- Improved graphics

 

[Brian Duddy]

Looks pretty good... if my laptop wasn't so terrible, I'd download it for sure >_>

Also, I loved those little physics posts you were doing... I know you have to develop the game of course, but if you could do any more of those, that would be good too...