Polyline Sandcastle Example edited

require(['Cesium'], function(Cesium) {
    "use strict";

    var viewer = new Cesium.Viewer('cesiumContainer');
    var scene = viewer.scene;
    var primitives = scene.getPrimitives();
    var ellipsoid = viewer.centralBody.getEllipsoid();


    var FS ="varying vec4 v_color;\n" +
            "void main() {\n" +
            "   vec4 outputColor = v_color;\n" +
            "   if (outputColor.a > 0.5) {\n" +
            "       outputColor.a = 0.0;\n" +
            "   } else {\n" +
            "       outputColor.a = 1.0;\n" +
            "   }\n" +
            "   gl_FragColor = outputColor;\n" +
            "}\n";

    var positions = [];
    var colors = [];
    for (var i = 0; i < 10; ++i) {
        positions.push(ellipsoid.cartographicToCartesian(Cesium.Cartographic.fromDegrees(-100.0 + i, 35.0)));
        colors.push(new Cesium.Color(0.0, 0.5, 1.0, i));
    }

    var prim = new Cesium.Primitive({
        geometryInstances : new Cesium.GeometryInstance({
            geometry : new Cesium.PolylineGeometry({
                positions : positions,
                width : 10.0,
                vertexFormat : Cesium.PolylineColorAppearance.VERTEX_FORMAT,
                colors : colors
            })
        }),
        appearance : new Cesium.PolylineColorAppearance()
    });

    prim.appearance.fragmentShaderSource = FS;

    primitives.add(prim);

    Sandcastle.finishedLoading();
});