Again some (newbie) ogreode questions

[charlie]

I'm not sure if this is the right place to ask... but anyway

* basically for playing around I extended the landscape demo. Now, I have a cool and speedy car (just entered a higher value for RPM) but it lacks wheel grip. (is this the correct word?). How can I get a better grip?

* what exactly is this ERP and CFM? It can be set to the world object. I read the ode manual, but unfortunately I didn't get what they meant. (never dealed with physics (except in real life ) before)

* a basic question about units: what is the unit of the number I e.g. apply for the gravity, or the mass of the wheels, car,....

* the least important question: is there a easy possibility to drive reverse? I already tryed to apply a negative power value to the wheel, but this didn't work. (I thought, worked for the steer, to inverse it, let's try... [clumsy beginner approche, I guess] )

[julian]

Hallo!
I'm new to ogre too and wanted to ask if you have an answer to youre questions, since I have pretty much the same and your post is rather old. So I though you might already have the answers to these questions? Would you mind shareing your thoughts, or does someone else have an idea?

I'm not sure if this is the right place to ask... but anyway

* basically for playing around I extended the landscape demo. Now, I have a cool and speedy car (just entered a higher value for RPM) but it lacks wheel grip. (is this the correct word?). How can I get a better grip?

* what exactly is this ERP and CFM? It can be set to the world object. I read the ode manual, but unfortunately I didn't get what they meant. (never dealed with physics (except in real life ) before)

* a basic question about units: what is the unit of the number I e.g. apply for the gravity, or the mass of the wheels, car,....

* the least important question: is there a easy possibility to drive reverse? I already tryed to apply a negative power value to the wheel, but this didn't work. (I thought, worked for the steer, to inverse it, let's try... [clumsy beginner approche, I guess] )

[Phantom]

* what exactly is this ERP and CFM? It can be set to the world object. I read the ode manual, but unfortunately I didn't get what they meant. (never dealed with physics (except in real life ) before)

* a basic question about units: what is the unit of the number I e.g. apply for the gravity, or the mass of the wheels, car,....

1st: ERP : Error reduction parameter
This is how fast(hard) constraints are forced back to a "valid" state if they drift away. (For example, if a large force causes the ball to go away from the socket in a ball constraint, this is how fast (or how much force) is applied to correct this(set the ball back in the socket)
CFM: Constraint force mixing
This is just basically how "soft" or hard the constraint is.

Usually you only need to adjust those if something in the simulation is unstable or jumpy. And then just tweaking around is the only way to get the desired effect.

Best way to see what they do is just binding some keys to increase and decrease erp and cfm, so you concretely see while the simulation is running what changes.
The ode manual explains them quite well so re-reading it should clear things up...

2nd: There is no set standard to the units. Usually real units aren't used in simulations. The basic approach is to just tweak around untill it looks real.

You can ofcourse use units, but then you have to be carefull not to mix them( e.q. once use kg, then g)
I personally have never used real units. So no guarantee how it works.

[julian]

Thanks a lot. Now I understand some more things

However even playing around with all those parameters I didn't get a better grip on the landscape example. (charlies first question). Since the ground ist reallllllllyyyyyyy slippery....

(

basically for playing around I extended the landscape demo. Now, I have a cool and speedy car (just entered a higher value for RPM) but it lacks wheel grip. (is this the correct word?). How can I get a better grip?

)

[Phantom]

Sorry, I can't help with Ogreode and grip, I haven't used ogreode that much yet.
(Even in ode I don't at the moment remember how to adjust it)

[charlie]

@julian:

I though you might already have the answers to these questions?

Sorry, but in the last few weeks I had no time playing with ogre since I had to write a project for my studies (Java stuff ).
So I don't had a look at these questions any more.

Concerning the thing with the grip, you might try to contact monster, who is the god (and creator) of ogreode. He definitly knows what you want. But if you find out, how to get more grip in the landscape example, please let me know or post in this thread, because once I've time again I'll have this problem, too (again)

@Phantom88: Thanks for the explaination of ERP and CFM? Finally I understand.

[monster]

In LandscapeApplication::collision change the bit that says setCoulombFriction.

And if you're using the RC1 version then in SimpleScenes.ogreode change the contact definition in the wheel definition of the "Jeep" vehicle.

To get the vehicle to reverse you need to add all the missing bits to the Vehicle class, so that if you're in reverse gear then a negative torque gets applied to the driving wheels.

Sorry I don't have time for a more detailed answer.