      .attr("id", "rectClip")
            .append("rect")
            .attr('class', 'rect-clip')
            .attr("width", 0)
            .attr("height", innerHeight);

            g.selectAll("path")
            .data(layers)
            .join("path") // use join to avoid split according to "enter" and "update"; 
            .attr("opacity",0.9)
            //.transition().duration(3000)
            .attr("d", function(d,i) {
                return area(d);
            })
            .attr("clip-path", "