First of all, I'll just paste my general setup here for reference:
centerOfMass = btVector3(0.f, 0.3f, 0.08f);
btCollisionShape * chassisShape = new btBoxShape(btVector3(0.5f, 0.2f, 0.625f));
btCompoundShape * compound = new btCompoundShape();
//localTrans effectively shifts the center of mass with respect to the chassis
tr.setOrigin(btVector3(0, 0, 0));
carChassis = CreateRigidBody(tr, compound, GetMotionState());
The Kart tips over very easily.
We use a low center of mass along with a Roll Influence value of 1.
Steering is all or nothing
Are you changing your steering value over time or directly setting it upon a key press? You need to make sure the turning happens over time (just like a real car).
Do you guys use OgreBullet to handle your physics?
No, I wrote my own wrapper as we needed to simulate most of the physics on the server which doesn't have any concept of Ogre.
How do you get your karts so low to the ground
This was just a matter of tweaking the suspension and mass until it looked and felt right.
Anytime I lower the box closer to the road, the box will hit parts of the road ( especially when going up a ramp or anything similar ).
Try stiffening your suspension I suppose. We had the same problem when the kart hit a ramp too fast. To fix this we designed our ramps on a curve instead of a hard angle.
Are you using just a bounding box for the car
Yep. btCollisionShape * chassisShape = new btBoxShape(btVector3(0.5f, 0.2f, 0.625f));
How do you make your suspension almost non-existent
It actually does exist and is necessary to give the whole thing some damping upon landing from a ramp, etc. It isn't visible on the client because I don't send the wheel positions over the network. It was determined to be too much data to transfer for something that isn't even expected on a kart type vehicle.
Here are the suspension values we use:
SuspensionStiffness = 100
SuspensionDamping = 20
SuspensionCompression = 4.2
SuspensionRestLength = 0.3
(Note: these values are most likely dependent on other values such as mass)
Are your vehicles front wheel, rear wheel, or 4 wheel drive?
2 rear wheel drive.
What is the average mass your using for vehicles
We use 400 now for all our karts.
Hope the info helps. Good luck!