Make distance display condition property dynamic.

[bagnell]

Make geometry distance display conditions able to be dynamic. Also fixed an issue with billboard and label when toggling clustering.

@mramato Are there any tests for dynamic geometry attributes?

[mramato]

@mramato Are there any tests for dynamic geometry attributes?

Unfortunately not, this is one of the least covered areas of the code (and something I'd really like to clean up when time allows).

[mramato]

@bagnell do you have the Sandcastle example you were using when you originally found this issue? Thanks.

[bagnell]

Here is the Sandcastle example I was using for testing. Toggling the enable flag was causing the crash in EntityCluster. Switching the labels to billboards caused another.

    var viewer = new Cesium.Viewer('cesiumContainer');

    var dataSource = new Cesium.GeoJsonDataSource();
    dataSource.clustering.enabled = true;

    function getDistance(entity, boundingSphere) {
        var ellipsoid = Cesium.Ellipsoid.WGS84;

        var center = boundingSphere.center;
        var radius = boundingSphere.radius;
        var eastNorthUp = Cesium.Transforms.eastNorthUpToFixedFrame(center, ellipsoid);
        var eastNorthUpRotation = Cesium.Matrix4.getRotation(eastNorthUp, new Cesium.Matrix3());
        var localX = Cesium.Matrix3.getColumn(eastNorthUpRotation, 0, new Cesium.Cartesian3());
        var localY = Cesium.Matrix3.getColumn(eastNorthUpRotation, 1, new Cesium.Cartesian3());
        var scaledX = Cesium.Cartesian3.multiplyByScalar(localX, radius, localX);
        var scaledY = Cesium.Cartesian3.multiplyByScalar(localY, radius, localY);

        var cartesianArray = new Array(4);
        cartesianArray[0] = Cesium.Cartesian3.add(center, scaledX, new Cesium.Cartesian3());
        cartesianArray[1] = Cesium.Cartesian3.add(center, Cesium.Cartesian3.negate(scaledX, scaledX), new Cesium.Cartesian3());
        cartesianArray[2] = Cesium.Cartesian3.add(center, scaledY, new Cesium.Cartesian3());
        cartesianArray[3] = Cesium.Cartesian3.add(center, Cesium.Cartesian3.negate(scaledY, scaledY), new Cesium.Cartesian3());

        var rectangle = Cesium.Rectangle.fromCartesianArray(cartesianArray, ellipsoid);
        var approxCameraPosition = viewer.scene.camera.getRectangleCameraCoordinates(rectangle);
        return Cesium.Cartesian3.magnitude(approxCameraPosition) - ellipsoid.maximumRadius;
    }

    dataSource.entities.collectionChanged.addEventListener(function(collection, added, removed, changed) {
        var deffereds = [];
        var promises = [];

        var entities = added;
        var length = entities.length;
        for (var i = 0; i < length; ++i) {
            var entity = entities[i];
            var deffered = Cesium.when.defer();

            deffereds.push({deffered : deffered, entity : entity});
            promises.push(deffered.promise);
        }

        var removeEventListener = viewer.scene.postRender.addEventListener(function() {
            var length = deffereds.length;
            var defferedsToRemove = [];

            for (var i = 0; i < length; ++i) {
                var deffered = deffereds[i].deffered;
                var entity = deffereds[i].entity;

                var result = new Cesium.BoundingSphere();
                var status = viewer.dataSourceDisplay.getBoundingSphere(entity, true, result);
                if (status === Cesium.BoundingSphereState.DONE) {
                    deffered.resolve({entity : entity, boundingSphere : result});
                } else if (status === Cesium.BoundingSphereState.FAILED) {
                    deffered.reject();
                }

                if (status !== Cesium.BoundingSphereState.PENDING) {
                    defferedsToRemove.push(deffereds[i]);
                }
            }

            for (var j = 0; j < defferedsToRemove.length; ++j) {
                deffereds.splice(deffereds.indexOf(defferedsToRemove[j]), 1);
            }
        });

        Cesium.when.all(promises).then(function(values) {
            var length = values.length;
            for (var i = 0; i < length; ++i) {
                var entity = values[i].entity;
                var boundingSphere = values[i].boundingSphere;

                entity.position = boundingSphere.center;
                entity.label = {
                    show : new Cesium.CallbackProperty(function(time, result) {
                        return dataSource.clustering.enabled;
                    }, false),
                    text : entity.properties.name,
                    distanceDisplayCondition : new Cesium.CallbackProperty(function(time, result) {
                        if (!Cesium.defined(result)) {
                            result = new Cesium.DistanceDisplayCondition();
                        }
                        result.near = getDistance(entity, boundingSphere);
                        return result;
                    }, false)
                };
                entity.polygon.distanceDisplayCondition = new Cesium.CallbackProperty(function(time, result) {
                    if (!Cesium.defined(result)) {
                        result = new Cesium.DistanceDisplayCondition();
                    }
                    if (dataSource.clustering.enabled) {
                        result.far = getDistance(entity, boundingSphere);
                    } else {
                        result.far = Number.MAX_VALUE;
                    }
                    return result;
                }, false);
            }

            removeEventListener();
        });
    });

    var url = '../../SampleData/ne_10m_us_states.topojson';
    dataSource.load(url, { clampToGround : false });
    viewer.dataSources.add(dataSource);

    var viewModel = {
        enabled : dataSource.clustering.enabled
    };
    Cesium.knockout.track(viewModel);

    var toolbar = document.getElementById('toolbar');
    Cesium.knockout.applyBindings(viewModel, toolbar);

    Cesium.knockout.getObservable(viewModel, 'enabled').subscribe(
        function(newValue) {
            dataSource.clustering.enabled = newValue;
        }
    );

[mramato]

Looks good, thanks @bagnell.