public Vector3 GetCameraPosition ( StereoEye stereoEye )
{
if (stereoEye==StereoEye.Mono) return cameraMatrix .TranslationVector;
if (stereoEye==StereoEye.Left) return cameraMatrixL.TranslationVector;
if (stereoEye==StereoEye.Right) return cameraMatrixR.TranslationVector;
throw new ArgumentException("stereoEye");
}