[ODE] I have buckling joints with 4 wheeled vehicle

[Pawel S]

I found the carworld source a little bit hard to follow. Here is part of
what I use in my program. It simulates a streetracer. It can do fast accs
and nice drifts.

At program start:

World attributes:
	dWorldSetContactMaxCorrectingVel( MyWorld, 0.5 );
	dWorldSetContactSurfaceLayer( MyWorld, 0.01 );
	// Should this be updated every frame?
	dWorldSetCFM( MyWorld, 0.000005 );
	dWorldSetERP( MyWorld, 0.8 );

Body weights are:
	1600 kilograms for the car's body and
	30 kilograms each for wheels

fMaxSteeringAngle = 45.0 degrees
fSk = 100000.0 // spring
fDk = 3000.0 // damper
vUp = a global vector pointing stright up

Every frame:

	SimClock.Update();

	// update dampers
	SCALAR fERP, fCFM;
	fERP = SimClock.GetDeltaTime() * fSk / ( SimClock.GetDeltaTime() * fSk +
fDk );
	fCFM = 1.0 / ( SimClock.GetDeltaTime() * fSk + fDk );

	dJointSetHinge2Param( JointFL, dParamSuspensionERP, fERP );
	dJointSetHinge2Param( JointFL, dParamSuspensionCFM, fCFM );
	dJointSetHinge2Param( JointFR, dParamSuspensionERP, fERP );
	dJointSetHinge2Param( JointFR, dParamSuspensionCFM, fCFM );
	dJointSetHinge2Param( JointRL, dParamSuspensionERP, fERP );
	dJointSetHinge2Param( JointRL, dParamSuspensionCFM, fCFM );
	dJointSetHinge2Param( JointRR, dParamSuspensionERP, fERP );
	dJointSetHinge2Param( JointRR, dParamSuspensionCFM, fCFM );

	// setup front wheel turn
	cMatrix mSteering = TransformsSim.Body.mOrientation; // copy car body
orientation
	mSteering.RotateAxisAngle( vUp, -VehicleInputSim.fSteeringWheel *
fMaxSteeringAngle ); // rotate it

	// restrict front wheel rotation to the steering's right axis
	dBodySetFiniteRotationAxis( BodyWheelFL,
		mSteering.RowAsVector( cMatrix::RIGHT ).x,
		mSteering.RowAsVector( cMatrix::RIGHT ).y,
		mSteering.RowAsVector( cMatrix::RIGHT ).z );
	dBodySetFiniteRotationAxis( BodyWheelFR,
		mSteering.RowAsVector( cMatrix::RIGHT ).x,
		mSteering.RowAsVector( cMatrix::RIGHT ).y,
		mSteering.RowAsVector( cMatrix::RIGHT ).z );

	// restrict rear wheel rotation to car body's right axis
	dBodySetFiniteRotationAxis( BodyWheelRL,
		TransformsSim.Body.mOrientation.RowAsVector( cMatrix::RIGHT ).x,
		TransformsSim.Body.mOrientation.RowAsVector( cMatrix::RIGHT ).y,
		TransformsSim.Body.mOrientation.RowAsVector( cMatrix::RIGHT ).z );
	dBodySetFiniteRotationAxis( BodyWheelRR,
		TransformsSim.Body.mOrientation.RowAsVector( cMatrix::RIGHT ).x,
		TransformsSim.Body.mOrientation.RowAsVector( cMatrix::RIGHT ).y,
		TransformsSim.Body.mOrientation.RowAsVector( cMatrix::RIGHT ).z );

	// turn the front wheels
	dJointSetHinge2Param( JointFL, dParamVel, 50.0 * (
-VehicleInputSim.fSteeringWheel * fMaxSteeringAngle -
dJointGetHinge2Angle1( JointFL ) ) );
	dJointSetHinge2Param( JointFR, dParamVel, 50.0 * (
-VehicleInputSim.fSteeringWheel * fMaxSteeringAngle -
dJointGetHinge2Angle1( JointFR ) ) );

	// apply torque to rear wheels
	if ( ( VehicleInputSim.fEngineTorque != 0.0 ) && ( bKeyState[
KbKeys.Forward.nKeyCode ] || bKeyState[ KbKeys.Backward.nKeyCode ] ) )
	{
		dJointSetHinge2Param( JointFL, dParamVel2, 90.0 *
-VehicleInputSim.fEngineTorque );
		dJointSetHinge2Param( JointFR, dParamVel2, 90.0 *
-VehicleInputSim.fEngineTorque );
		dJointSetHinge2Param( JointRL, dParamVel2, 90.0 *
-VehicleInputSim.fEngineTorque );
		dJointSetHinge2Param( JointRR, dParamVel2, 90.0 *
-VehicleInputSim.fEngineTorque );

		SCALAR l_fTorque = 4500.0 * fabs( VehicleInputSim.fEngineTorque );
		dJointSetHinge2Param( JointFL, dParamFMax2, 0.0 );
		dJointSetHinge2Param( JointFR, dParamFMax2, 0.0 );
		dJointSetHinge2Param( JointRL, dParamFMax2, l_fTorque );
		dJointSetHinge2Param( JointRR, dParamFMax2, l_fTorque );
	}
	else
	{
		dJointSetHinge2Param( JointFL, dParamVel2, 0.0 );
		dJointSetHinge2Param( JointFR, dParamVel2, 0.0 );
		dJointSetHinge2Param( JointRL, dParamVel2, 0.0 );
		dJointSetHinge2Param( JointRR, dParamVel2, 0.0 );

		dJointSetHinge2Param( JointFL, dParamFMax2, 20.0 );
		dJointSetHinge2Param( JointFR, dParamFMax2, 20.0 );
		dJointSetHinge2Param( JointRL, dParamFMax2, 20.0 );
		dJointSetHinge2Param( JointRR, dParamFMax2, 20.0 );

		if ( VehicleInputSim.fBrakes > 0.0 )
		{
			dJointSetHinge2Param( JointFL, dParamVel2, 0.0 );
			dJointSetHinge2Param( JointFR, dParamVel2, 0.0 );
			dJointSetHinge2Param( JointRL, dParamVel2, 0.0 );
			dJointSetHinge2Param( JointRR, dParamVel2, 0.0 );

			dJointSetHinge2Param( JointFL, dParamFMax2, 3000.0 *
VehicleInputSim.fBrakes );
			dJointSetHinge2Param( JointFR, dParamFMax2, 3000.0 *
VehicleInputSim.fBrakes );
			dJointSetHinge2Param( JointRL, dParamFMax2, 3000.0 *
VehicleInputSim.fBrakes );
			dJointSetHinge2Param( JointRR, dParamFMax2, 3000.0 *
VehicleInputSim.fBrakes );
		}
	}

	// step world
	dSpaceCollide( WorldSpace, 0, &NearCallback );
	dWorldStep( MyWorld, SimClock.GetDeltaTime() );
	dJointGroupEmpty( MyContactGroup );


/Pawel S


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