Geojson GeometryCollection to Cesium entities

CesiumJS
1

Hi, we are having an issue displaying geojson features included in a geometry collection with extruded height.
We store the information about extruded height in gejson properties in case of a geometry collection as follows:

				"geometryExtension": {
					"geCollection": [
						{
							"extruded": {
								"maxHeight": 18000
								"minHeight": 1500
							}
						},
						{
							"extruded": {
								"maxHeight": 19000,
								"minHeight": 1600
							}
						}
					]
				}

The geometry collection for example looks like this:

  	"geometry": {
  		"type": "GeometryCollection",
  		"geometries": [
  			{
  				"type": "Point",
  				"coordinates": [
  					16.7,
  					48.2,
  					1500
  				]
  			},
  			{
  				"type": "Polygon",
  				"coordinates": [
  					[
  						[
  							16.75,
  							48.2,
  							1600
  						],
  						[
  							16.9,
  							48.2,
  							1700
  						],
  						[
  							16.9,
  							48.3,
  							1800
  						],
  						[
  							16.75,
  							48.2,
  							1600
  						]
  					]
  				]
  			}
  		]
  	}

This way we know that the first ‘extruded’ object belongs to the first geometry from the geometry collection and so on.

Since Cesium creates separate entities for each of the geometries form the collection, we are not able to relate the extruded information to the geometry sequence (index) after the data source has been initialized.

Do you have an idea how to keep the information about the order/sequence of the geometries form a geometry collection in the entities?

Any help on this would be very much appreciated.

2

You could add the extrusion information in the properties of the GeoJSON, like:

"geometries" : [{
                "type" : "MultiPolygon",
                "arcs" : [[[0]], [[1]], [[2, 3, 4, 5, 6, 7, 8, 9]]],
                "id" : "MA",
                "properties" : {
                    "name" : "Massachusetts",
                    "Statehood" : "Feb. 6, 1788",
                    "Population" : 6692824
                }
            }

From: https://raw.githubusercontent.com/CesiumGS/cesium/master/Apps/SampleData/ne_10m_us_states.topojson

Then in CesiumJS you can get these properties after you load the GeoJSON and use them for the extrusion:

entity.polygon.extrudedHeight =
          entity.properties.Population / 50.0;

From: https://sandcastle.cesium.com/index.html?src=GeoJSON%20and%20TopoJSON.html.

Let me know if this works for you.