Rotating A Wheeled Vehicle In Mid Air

First off I would like to think user Morrock for helping me in the irc chat with the math calculations.

Go to the rigid.h file in the game directory. At the very end of the Rigid class and add this line of code:

void applyRotationImpulse(const Point3F &rotation);

Now open up the rigid.cc file. At the very end of this file add:

void Rigid::applyRotationImpulse(const Point3F &rotation)
{	
	angMomentum += rotation;

	invWorldInertia.mulV(angMomentum, &angVelocity);
}

Ok, we now have set up the functions for rotation, but now we have to allow that rotation to effect the vehicle.

Open up the vehicle.h file in the game/vehicles directory. Locate the "Vehicle" class and then locate the object "Rigid mRigid". That is the rigid body of the car itself. Replace the "Rigid mRigid" line of code with this:

public:
   Rigid mRigid;

protected:

That allows the rigid body to be exposed to other functions.

Now open up the wheeledvehicle.cc file in the same directory and add this code to the very bottom:

ConsoleMethod(WheeledVehicle, applyRotationImpulse, void, 3, 3, "Spin the car. Usage: applyRotationImpulse(Vector3 rotation axis)")
{
	argc;
	

	Point3F force(0, 0, 0);
	dSscanf(argv[2],"%g %g %g",&force.x,&force.y,&force.z);

	object->mRigid.applyRotationImpulse(force);
}

That is the console function that you use to spin the car.

Recompile the engine.

NOW IT IS TIME TO TEST THIS BABY!!!!!

Open up Torque and make the vehicle airborne somehow. You might want to delete the terrain or something so that the vehicle can't land. To test this code, the vehicle must be in the air.

Once that is done, open up the console and type:

%car.applyRotationImpulse(MatrixMulVector(%car.getTransform(), "rotx roty rotz"));

NOTE!!!! You must replace the word %car with the name or ID of the vehicle you are rotating. AND you must replace rotx with the rotation force you want on the x axis, roty with the force on the y axis and rotz for the z axis!

Now hit enter. Your car should now rotate. If it doesn't rotate with a small value, try a higher one.

We had to use the MatrixMulVector so that the rotation axis will stay the same no matter where the car is facing.

I hope you liked this resource. Please leave a comment.

Thanks again to Morrock for the help with these code changes!