Polygon Clamp To Ground when terrain provider is used

CesiumJS
1

Hi
Link to Sandcastle: Sandcastle link

`const viewer = new Cesium.Viewer(“cesiumContainer”, {
terrainProvider : Cesium.createWorldTerrain(),
sceneMode: Cesium.SceneMode.SCENE3D,
timeline: false,
homeButton: false,
fullscreenButton: false,
animation: false,
geocoder: false,
creditDisplay: false,
msaaSamples: 2
});

const geoJSON = {“type”:“FeatureCollection”,“crs”:{“type”:“name”,“properties”:{“name”:“urn:ogc:def:crs:EPSG::4326”}},“features”:[{“type”:“Feature”,“geometry”:{“type”:“MultiPolygon”,“coordinates”:[[[[146.390265449,-41.28804605],[146.384301071,-41.287233314],[146.38362103,-41.290082095],[146.384482621,-41.290199449],[146.383826976,-41.293221767],[146.389166403,-41.293882235],[146.388974991,-41.293433771],[146.388974991,-41.293433771],[146.390265449,-41.28804605]]]]},“properties”:{“Description”:null,“Label”:null,“Name”:“BOUNDARY”}},{“type”:“Feature”,“geometry”:{“type”:“MultiPolygon”,“coordinates”:[[[[146.389467845,-41.29137588],[146.398598169,-41.291093358],[146.398394091,-41.289088423],[146.398277399,-41.287823133],[146.398286404,-41.287359851],[146.398493275,-41.286626757],[146.398762258,-41.286304368],[146.399068821,-41.286067956],[146.399223129,-41.285933356],[146.400089334,-41.285534888],[146.400739229,-41.285297806],[146.401155672,-41.285082055],[146.401549414,-41.284677671],[146.401893332,-41.2839876],[146.39447634,-41.284341211],[146.391253322,-41.283910841],[146.390265449,-41.28804605],[146.389467845,-41.29137588]]]]},“properties”:{“Description”:null,“Label”:null,“Name”:“BOUNDARY”}}]};

const promise = Cesium.GeoJsonDataSource.load(geoJSON);

promise.then(function (dataSource) {
viewer.dataSources.add(dataSource);
viewer.flyTo(dataSource);
const entities = dataSource.entities.values;
for (let i = 0; i < entities.length; i++) {
const entity = entities[i];
entity.polygon.material = Cesium.Color.CYAN.withAlpha(0.5);
entity.polygon.outline = true;
entity.polygon.outlineColor = Cesium.Color.BLACK;
entity.polygon.heightReference =
Cesium.HeightReference.CLAMP_TO_GROUND;
}
});`

When the terrain provider is not used the polygon is formatted as follows:
image

However when the terrain provider is given the polygon is formatted as follows:
image

How can we achieve the same formatting with the TerrainProvider
Any help is highly appreciated
Thanks
Sakna

2

Hi, Are you looking for GeoJsonDataSource.clampToGround?
I’ve modified your example. But it will not work with the outline and explicit height.

  • Best Regards
1 Like
3

Is there any work around to get an outline and have it clamp to terrain?

4

Hi Jacky,

Thanks for this. I tried clamping to ground as well. However, when I try to set the outline it does not work.

Thanks

5

I don’t think so because there is a an issue registered.

Only thing that worked so far is not using a terrainProvider

6

You can do that if you separately create polygon and polyline entities instead of create them all at once though datasource. I’ve re-modified above sandcastle example to make it working.

1 Like
7

Thanks Jacky for this