Function computeTankDiff

physx/source/physxvehicle/src/PxVehicleUpdate.cpp:1675–1751

///////////////////////////////////////////////////////

void computeTankDiff
(const PxF32 thrustLeft, const PxF32 thrustRight, 
 const PxU32 numActiveWheels, const bool* activeWheelStates, 
 PxF32* aveWheelSpeedContributions, PxF32* diffTorqueRatios, PxF32* wheelGearings)
{
	const PxF32 thrustLeftAbs=PxAbs(thrustLeft);
	const PxF32 thrustRightAbs=PxAbs(thrustRight);

	//Work out now many left wheels are enabled.
	PxF32 numLeftWheels=0.0f;
	for(PxU32 i=0;i<numActiveWheels;i+=2)
	{
		if(activeWheelStates[i])
		{
			numLeftWheels+=1.0f;
		}
	}
	const PxF32 invNumEnabledWheelsLeft = numLeftWheels > 0 ? 1.0f/numLeftWheels : 0.0f;

	//Work out now many right wheels are enabled.
	PxF32 numRightWheels=0.0f;
	for(PxU32 i=1;i<numActiveWheels;i+=2)
	{
		if(activeWheelStates[i])
		{
			numRightWheels+=1.0f;
		}
	}
	const PxF32 invNumEnabledWheelsRight = numRightWheels > 0 ? 1.0f/numRightWheels : 0.0f;

	//Split the diff torque between left and right.
	PxF32 diffTorqueRatioLeft=0.5f;
	PxF32 diffTorqueRatioRight=0.5f;
	if((thrustLeftAbs + thrustRightAbs) > 1e-3f)
	{
		const PxF32 thrustDiff = 0.5f*(thrustLeftAbs - thrustRightAbs)/(thrustLeftAbs + thrustRightAbs);
		diffTorqueRatioLeft += thrustDiff;
		diffTorqueRatioRight -= thrustDiff;

	}
	diffTorqueRatioLeft *= invNumEnabledWheelsLeft;
	diffTorqueRatioRight *= invNumEnabledWheelsRight;

	//Compute the per wheel gearing.
	PxF32 wheelGearingLeft=1.0f;
	PxF32 wheelGearingRight=1.0f;
	if((thrustLeftAbs + thrustRightAbs) > 1e-3f)
	{
		wheelGearingLeft=computeSign(thrustLeft);
		wheelGearingRight=computeSign(thrustRight);
	}

	//Compute the contribution of each wheel to the average speed at the clutch.
	const PxF32 aveWheelSpeedContributionLeft = 0.5f*invNumEnabledWheelsLeft;
	const PxF32 aveWheelSpeedContributionRight = 0.5f*invNumEnabledWheelsRight;

	//Set all the left wheels.
	for(PxU32 i=0;i<numActiveWheels;i+=2)