protected Quaternion GetLightOrientation()
{
Vector3 zAdjustVec = -light.DerivedDirection;
Vector3 xAxis, yAxis, zAxis;
Quaternion orientation = ( lightNode == null ) ? Quaternion.Identity : lightNode.DerivedOrientation;
// Get axes from current quaternion
// get the vector components of the derived orientation vector
orientation.ToAxes( out xAxis, out yAxis, out zAxis );
Quaternion rotationQuat;
if ( ( zAxis + zAdjustVec ).LengthSquared < 0.00001f )
{
// Oops, a 180 degree turn (infinite possible rotation axes)
// Default to yaw i.e. use current UP
rotationQuat = Quaternion.FromAngleAxis( Utility.PI, yAxis );
}
else
{
// Derive shortest arc to new direction
rotationQuat = zAxis.GetRotationTo( zAdjustVec );
}
return rotationQuat * orientation;
}
}
