Not understanding a piece of RayCastCar code

[Auradrummer]

Hello guys,

I noticed that the function SubmitConstrainst is called every time, but I'm not found the calling anywhere. How can it be?

[Julio Jerez]

that's a callback called by the engine. you do not call it yourself

[Auradrummer]

I'm still studying the raycast code here, I want to understand it completely, so I can implement some weird things I want (like mechanical failures to the car during race). If I have another thing I can't understand I'll bother you again . Thanks!

[Auradrummer]

Let's me explain one thing before proceed: all my difficulties is because I'm not using Newton as renderer, I'm using it only to manage physics. So, I cannot use the exact code that comes with the example, I have to make some interfaces that are very hard for me, that am a beginner.

But I'm advancing, the graphic tires are following the physical ones. But I'm with another problem. Originally, when I put some torque over the car, it spins crazy. I deduced that the torque was being set in side of rear wheels instead of in its heading. So, I searched some place in code where torque is applied, and I found these lines:

Code: Select all

line 400          m_chassisForce += chassisMatrix.m_front.Scale (tire.m_torque * - 40);
line 402          m_chassisForce += chassisMatrix.m_right.Scale(tire.m_turnforce * 60);


I thought that is the place where torque is applied. So, I exchanged the 'm_right' and 'm_front' vectors. The car, now moves forward. But, when I try to move it backwards it go shaking. I made something wrong?

[Dave Gravel]

You have surely a old beta because I have change this code part, the lines that you show at 400 and 402 is changed now...
You need to understand this vehicle is a raycast it don't have real tire.
The tire is totally a simulated effect and it is not a real body it don't have any real contact.
It behaving like a air hockey game, http://images.google.com/images?q=air%2 ... =fr&tab=wi

The torque that you can find in the code is only a simulation to simulate the visual tire rotation mesh, but the tire in self don't rotate at all.
Imagine a vehicle floating like the air hockey puck but the chassis rotation is limited by some magical force, like a joint can do...
In reallity the torque is apply on the tire position like a stabilizator to stabilize the final chassis movement.
In final a force is mix with this toque at the tire position for push the vehicle chassis to make it sliding,floating on air like a real acceleration effect.

All force and torque, velocity, omega, and the joint all is based on the chassis matrix and on the tire suspenssion matrix and on the tire pos.
If you start to change some direction in the code for try to fix your problem, you have real chances to scrap all in final...
The best is to use the default code setup, and at place to change direction in the code change your vehicle mesh collision direction.
You can do this with 3d modeler or use the offsetmatrix, to fix your chassis direction with the default code setup.
When you get it right after it's a lot more simple to rotate and place your vehicle in any direction and position...

by Julio Jerez » Mon Feb 09, 2009 11:45 pm
that's a callback called by the engine. you do not call it yourself

Some callback can come called by yourself exemple with material but it is really rare, and you need to call it in a other callback with the same type.
Or maybe i'm wrong here, I have already do this in old version maybe now it's not possible with new version.
In reallity you only need to assign it on a pointer or with a newton command.


Good luck.

[Auradrummer]

Ok Dave, is really a totally new concept of making a car, and I faced great difficulties, that are slowly going away. I'll downloaded another copy of Newton Dynamics to make some tries. I think 75% of the code are understood now. Working hard for the next 25%.

Thanks a lot for your good post!

[Auradrummer]

Hey, I just compiled the demos. The only thing I had to fix is adding the -pthread instruction in the LIBS.

Look how strange is the Raycast cars...
http://img120.imageshack.us/my.php?image=capturadatelanewtonarchde5.png

[Julio Jerez]

you have an older sdk, you need to download this one.
http://www.newtondynamics.com/downloads ... n-2.00.rar

[Auradrummer]

PAGE NOT FOUND.

[Julio Jerez]

viewtopic.php?f=9&t=4922

[Auradrummer]

Same problem ... could be some definition of Linux?

[Auradrummer]

I solved here the problem of the car shaking when goes rear. Was the Center of Mass Offset. With a 0.6f the car was raising the front when torque is set and was too heavy to raise when car goes back. I think I could solve this by tunning the suspension. But, problem solved anyway.

[Dave Gravel]

With a 0.6f

Use lower value exemple 0.06 and reduce the friction a lot something like 0.5

[Auradrummer]

Ok. Now I'm using your custom RayCast car (that DG is from David Gravel, right?).

I'm proceeding with the adaptations of your code to my needs here, let's see what will happens...