void UpdateEyeViewProperties()
{
if ((dirtyFlags & DirtyFlags.EyeViewProperties) != 0)
{
Matrix.Invert(ref eyeView, out invertEyeView);
eyePosition = invertEyeView.Translation;
eyeDirection = invertEyeView.Forward;
eyeDirection.Normalize();
eyeUp = invertEyeView.Up;
eyeUp.Normalize();
dirtyFlags &= ~DirtyFlags.EyeViewProperties;
}
}