Cesium.PolylineGeometry不工作。Cesium.SimplePolylineGeometry做的

Question

我以这样的方式创建Cesium.Primitive：

    _createPrimitive: function (linesNumber) {
        var instances = [];
        for (var i = 0; i < linesNumber; i++) {
            var lon = _.random(-90, 90);
            var lat = _.random(-180, 180);
            var polyline = new Cesium.SimplePolylineGeometry({
                positions: Cesium.Cartesian3.fromDegreesArrayHeights([
                    lat, lon, 0,
                    lat, lon, 2000000])
            });
            var geometry = Cesium.SimplePolylineGeometry.createGeometry(polyline);
            instances.push(new Cesium.GeometryInstance({
                geometry: geometry,
                attributes: {
                    color: Cesium.ColorGeometryInstanceAttribute.fromColor(Cesium.Color.fromRandom({alpha: 1}))
                }
            }));
        }
        return new Cesium.Primitive({
            geometryInstances: instances,
            appearance: new Cesium.PerInstanceColorAppearance()
        });
    },

然后再添加到场景中：

scene.primitives.add(this._createPrimitive(20000));

它如预期的那样工作。我想改变polyline的宽度。我将Cesium.SimplePolylineGeometry更改为Cesium.PolylineGeometry，并在Cesium.PolylineGeometry构造函数调用中添加width param：

    _createPrimitive: function (linesNumber) {
        var instances = [];
        for (var i = 0; i < linesNumber; i++) {
            var lon = _.random(-90, 90);
            var lat = _.random(-180, 180);
            var polyline = new Cesium.PolylineGeometry({
                positions: Cesium.Cartesian3.fromDegreesArrayHeights([
                    lat, lon, 0,
                    lat, lon, 2000000]),
                width: 4
            });
            var geometry = Cesium.PolylineGeometry.createGeometry(polyline);
            instances.push(new Cesium.GeometryInstance({
                geometry: geometry,
                attributes: {
                    color: Cesium.ColorGeometryInstanceAttribute.fromColor(Cesium.Color.fromRandom({alpha: 1}))
                }
            }));
        }
        return new Cesium.Primitive({
            geometryInstances: instances,
            appearance: new Cesium.PerInstanceColorAppearance()
        });
    },

地球是空的！我做错了什么？

Answer 1

问题是，我使用了不适当的appearance：Cesium.PolylineColorAppearance，例如，工作得很好：

    return new Cesium.Primitive({
        geometryInstances: instances,
        appearance: new Cesium.PolylineColorAppearance()
    });