Class MovingFrame

extensions/flexExtMovingFrame.cpp:13–82

// our math types on the API

struct MovingFrame
{
	Vec3 position;	
	Quat rotation;

	Vec3 velocity;
	Vec3 omega;

	Vec3 acceleration;
	Vec3 tau;

	Matrix44 delta;

	MovingFrame(Vec3 worldTranslation, Quat worldRotation)
	{
		position = worldTranslation;
		rotation = worldRotation;
		delta = Matrix44::kIdentity;
	}
	
	// update the frame, returns a matrix representing the delta transform that 
	// can be applied to particles to teleport them to the frame's new location
	void Move(Vec3 newPosition, Quat newRotation, float dt)
	{
		const float invDt = 1.0f/dt;

		// calculate new velocity
		Vec3 newVelocity = (newPosition-position)*invDt;
		Vec3 newOmega = 2.0f*Vec3(Quat(newRotation-rotation)*Inverse(rotation)*invDt);

		// calculate new acceleration
		Vec3 newAcceleration = (newVelocity-velocity)*invDt;
		Vec3 newTau = (newOmega-omega)*invDt;

		// calculate delta transform
		Matrix44 LocalFromOld = AffineInverse(TranslationMatrix(Point3(position))*RotationMatrix(rotation));
		Matrix44 NewFromLocal = TranslationMatrix(Point3(newPosition))*RotationMatrix(newRotation);
		
		// update delta transform
		delta = NewFromLocal*LocalFromOld;

		// position
		position = newPosition;
		rotation = newRotation;

		// update velocity
		velocity = newVelocity;
		omega = newOmega;

		acceleration = newAcceleration;
		tau = newTau;
	}

	inline Vec3 GetLinearForce() const
	{
		return -acceleration;
	}