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();

    // start and end points on the surface of the earth
    var startPoint = ellipsoid.cartographicToCartesian(Cesium.Cartographic.fromDegrees(-90, 40, 0.0));
    var endPoint = ellipsoid.cartographicToCartesian(Cesium.Cartographic.fromDegrees(-80, 40, 0.0));
    var midpointCartesian = ellipsoid.cartographicToCartesian(Cesium.Cartographic.fromDegrees(-85, 45, 0.0));

    // create a hermite spline that goes through these three points
    var hermiteSpline = new Cesium.HermiteSpline({
        times : [ 0.0, 0.5, 1.0 ],
        points : [
            startPoint,
            midpointCartesian,
            endPoint
        ]
    });

    // create a 20 point polyline that follows the spline
    var polylinePoints = [];
    for(var i=0; i<20; ++i) {
        polylinePoints.push(hermiteSpline.evaluate(i/20));
    }

    var polylineCollection = new Cesium.PolylineCollection();
    var polyline = polylineCollection.add();
    polyline.setPositions(polylinePoints);

    primitives.add(polylineCollection);

    // Red tube
    var redTube = new Cesium.GeometryInstance({
        geometry : new Cesium.PolylineVolumeGeometry({
            polylinePositions : polylinePoints,
            vertexFormat : Cesium.PerInstanceColorAppearance.VERTEX_FORMAT,
            shapePositions : Cesium.Shapes.compute2DCircle(60000),
            cornerType : Cesium.CornerType.ROUNDED
        }),
        modelMatrix: Cesium.Matrix4.multiply(
            Cesium.Matrix4.IDENTITY, Cesium.Matrix4.fromRotationTranslation(Cesium.Matrix3.fromRotationY(0.2), new Cesium.Cartesian3(0.0, 0.0, 0.0))),
        attributes : {
            color : Cesium.ColorGeometryInstanceAttribute.fromColor(Cesium.Color.RED)
        }
    });

    // Add instances to primitives
    primitives.add(new Cesium.Primitive({
        geometryInstances : [redTube],
        appearance : new Cesium.PerInstanceColorAppearance({
                translucent : false,
                closed : true
            })
        }));

    Sandcastle.finishedLoading();
});