如何更改俩条线段相交时节点的样式

例如我想做成上图的样子

Path myPath = new Path();
StreamGeometry geometry = new StreamGeometry();

        using (StreamGeometryContext ctx = geometry.Open())
        {
            ctx.BeginFigure(localPath[0], true, true);
            ctx.PolyLineTo(localPath, true, true);  
        }
        geometry.Freeze();
        myPath.Data = geometry;
        //边框的颜色
        myPath.Stroke = Brushes.Red;
        //边框的粗细
        myPath.StrokeThickness = 20;
        //圆弧角
        myPath.StrokeLineJoin = PenLineJoin.Round;