/// <summary>
/// Recalculates the ViewerAngle property based on a viewer's position.
/// </summary>
/// <param name="ViewerPosition"></param>
public void UpdateViewerAngle(V2 ViewerPosition)
{
V2 direction = TargetObject.Position2D - Position2D;
direction.Normalize();
ushort angle = MathUtil.GetAngleForDirection(direction);
// update viewer angle
ViewerAngle = MathUtil.GetAngle(ViewerPosition, Position2D, angle);
// mark for possible appearance change
appearanceChanged = true;
}