KmlDataSource (Polyline) vs clampToGround

[jaforom]

Dears,

The clampToGround property doesn't seem to go right with KML LineString (it's ok with Polygon and Point). Here it is the example code:

var viewer = new Cesium.Viewer('cesiumContainer');
var cesiumTerrainProviderMeshes = new Cesium.CesiumTerrainProvider({
    url : 'https://assets.agi.com/stk-terrain/world',
    requestWaterMask : true,
    requestVertexNormals : true
});
viewer.terrainProvider = cesiumTerrainProviderMeshes;

Sandcastle.addDefaultToolbarMenu([{
    text : 'Polygon',
    onselect : function() {
        var ds = Cesium.KmlDataSource.load(
            'http://visortf.grafcan.es/KML/rep/Sand_Polygon.kml',
            {
                camera: viewer.scene.camera,
                canvas: viewer.scene.canvas,
                clampToGround:true
            }
        );
        Cesium.when(ds,function(dataSource) {
            viewer.dataSources.add(dataSource);
            viewer.flyTo(dataSource);
        });
    }
}, {
    text : 'Polyline',
    onselect : function() {
        var ds = Cesium.KmlDataSource.load(
            'http://visortf.grafcan.es/KML/rep/Sand_Polyline.kml',
            {
                camera: viewer.scene.camera,
                canvas: viewer.scene.canvas,
                clampToGround:true
            }
        );
        Cesium.when(ds,function(dataSource) {
            viewer.dataSources.add(dataSource);
            viewer.flyTo(dataSource);
        });
    }
}], 'zoomButtons');

Sandcastle.reset = function () {
    viewer.entities.removeAll();
    viewer.dataSources.removeAll();
};

• First combo item: Sand_Polygon.kml (a single polygon and no style).
• Second combo item: Sand_Polyline.kml contains a single polyline with no style, too.

I don't know if I'm doing something wrong...

Regards

[hpinkos]

Hello @jaforom
Cesium does not yet have support for polylines on terrain. It's on our roapmap, but we need to do a bit more research to figure out the best way to implement it.
Thanks!

[mramato]

The latest version of Cesium converts LineString to entity corridors if clampToGround is set to true. This looks like a valid bug to me. @tfili can you take a look?

[denverpierce]

The tested KML doesn't have <tessellate> so it returns undefined when cesium checks for clamp-ability.

https://github.com/AnalyticalGraphicsInc/cesium/blob/master/Source/DataSources/KmlDataSource.js#L1148

[jaforom]

Ok, I see. But Cesium fails if the LineString is styled and tessellate is true (1):

Cesium.js:477 An error occurred while rendering.  Rendering has stopped.
undefined
TypeError: r.getType is not a function
TypeError: r.getType is not a function
    at Function.o.getValue (http://.../Cesium/last/Cesium.js:445:2670)
    at a.update (http://.../Cesium/last/Cesium.js:450:16643)
    at s.update (http://.../Cesium/last/Cesium.js:450:19123)
    at m.update (http://.../Cesium/last/Cesium.js:451:844)
    at x.update (http://.../Cesium/last/Cesium.js:456:26898)
    at X._onTick (http://.../Cesium/last/Cesium.js:479:25189)
    at r.raiseEvent (http://.../Cesium/last/Cesium.js:423:24345)
    at u.tick (http://.../Cesium/last/Cesium.js:431:6066)
    at A.render (http://.../Cesium/last/Cesium.js:477:3022)
    at t (http://.../Cesium/last/Cesium.js:476:25339)

[jaforom]

I forgot to comment that I modified the sample KML, http://visortf.grafcan.es/KML/rep/Sand_Polyline.kml, and I included the following elements: tessellate and Style.

[denverpierce]

That looks legit. The override clamped corridors are getting Cesium Colors from the polyline, instead of new ColorMaterialProperties.

[pjcozzi]

Please test out the fix in #4157 kindly contributed by @AndreyOrlov.