Update function at page 48

[v71]

I am at page 48 and actually using this code, but there is something wrong , and the sphere simply don't appear
what am i doing wrong ? i am sure i have follwed exactly the code in the book

` void Update(const float dt_sec)
{
m_position += m_linearVelocity * dt_sec;

	// okay, we have an angular velocity around the center of mass, this needs to be
	// converted somehow to relative to model position.  This way we can properly update
	// the orientation of the model.
	
	Vec3 positionCM = GetCenterOfMassWorldSpace();  
	Vec3 cmToPos = m_position - positionCM;  

	// Total Torque is equal to external applied torques + internal torque (precession)
	// T = T_external + omega x I * omega
	// T_external = 0 because it was applied in the collision response function
	// T = Ia = w x I * w
	// a = I^-1 ( w x I * w )

	Mat3 orientation = m_orientation.ToMat3();  
	Mat3 inertiaTensor = orientation * m_shape->InertiaTensor() * orientation.Transpose (); 
	Vec3 alpha = inertiaTensor.Inverse() * (m_angularVelocity.Cross (inertiaTensor *  m_angularVelocity));  
	m_angularVelocity += alpha * dt_sec;  
	// Update orientation 
	
	Vec3 dAngle = m_angularVelocity * dt_sec;  
	Quat dq = Quat (dAngle, dAngle. GetMagnitude ());  
	m_orientation = dq * m_orientation;  
	m_orientation.Normalize ();  
	
	// Now ge t the new model position  
	m_position = positionCM + dq.RotatePoint(cmToPos);  
	
}
`