public RectangleVisibilityBlocker(RectangleF rect, Visibility.OcclusionLevel occlusionLevel = Visibility.OcclusionLevel.Obscured) : base(occlusionLevel)
 {
     this.Rect = rect;
 }
 public LineVisibilityBlocker(MMath.LineSegment line, Visibility.OcclusionLevel occlusionLevel = Visibility.OcclusionLevel.Obscured) : base(occlusionLevel)
 {
     this.Line = line;
 }
 public VisibilityBlocker(Visibility.OcclusionLevel occlusionLevel = Visibility.OcclusionLevel.Obscured)
 {
     this.OcclusionLevel = occlusionLevel;
 }