How to use CesiumJS to visualize data from a Session
Revision as of 14:47, 1 March 2024 by Frank@tygron.nl (talk | contribs)
Most of the time you want to use the heightmap of your project's session, instead of the default digital elevation height that Cesium provides. Use this code for a custom heightmap provider.
// variables const dim = 128; const minLevel = 6; const maxLevel = 19; const tilepx = 512; // Construct the default list of terrain sources. var terrainModels = []; terrainModels.push(new Cesium.ProviderViewModel({ name: "Project Terrain", category: "Terrain", iconUrl: Cesium.buildModuleUrl('Widgets/Images/TerrainProviders/Ellipsoid.png'), creationFunction: function () { return new Cesium.CustomHeightmapTerrainProvider({ width: dim, height: dim, maximumLevel: maxLevel, callback: function (x, y, level) { if (level <= 10) { // ignore zoom levels 10 and lower return new Float32Array(dim * dim); // all zeros } const test = Cesium.Resource.fetchArrayBuffer('terrain/' + level + '/' + x + '/' + y + '.bin?worlddatum=true&token=$TOKEN&width=' + dim + '&height=' + dim); return test.then(function (buffer) { const array = new Float32Array(dim * dim); // all zeros const view = new DataView(buffer); for (let i = 0; i < dim * dim; i++) { array[i] = view.getFloat32(i * 4); } return array; }); }, }); } }));
You can use the following code to add and access your project's. Additionally, you can provide the optional layer parameter: SATELLITE, TOPOGRAPHIC or GRAY.
var imageryViewModels = []; const baseMaps = ["SATELLITE", "TOPOGRAPHIC", "GRAY"]; for (let i = 0; i < baseMaps.length; i++) { imageryViewModels.push(new Cesium.ProviderViewModel({ name: baseMaps[i], category: "Base Map", iconUrl: Cesium.buildModuleUrl('Widgets/Images/TerrainProviders/Ellipsoid.png'), creationFunction: function () { return new Cesium.WebMapServiceImageryProvider({ url: 'wms', layers: baseMaps[i], maximumLevel: maxLevel, tileHeight: tilepx, tileWidth: tilepx, getFeatureInfoFormats: [new Cesium.GetFeatureInfoFormat("json", "application/json")], proxy: new Cesium.DefaultProxy('/proxy/'), parameters: { crs: "4326", forcexy: "true", bgcolor: "$BGCOLOR", walled: "false", token: "$TOKEN" }, getFeatureInfoParameters: { crs: "4326", forcexy: "true", token: "$TOKEN", }, clock: WMS_CLOCK, times: WMS_TIMES }); } })); }
The Cesium viewer is initialized as followed:
// Construct the viewer, with a high-res terrain source pre-selected. var viewer = new Cesium.Viewer('cesiumContainer', { terrainProviderViewModels: terrainModels, selectedTerrainProviderViewModel: terrainModels[0], imageryProviderViewModels: imageryViewModels, selectedImageryProviderViewModel: imageryViewModels[$BASEMAP_INDEX], animation: false, timeline: false, homeButton: false, navigationHelpButton: false, navigationInstructionsInitiallyVisible: false, fullscreenButton: false, shadows: $SHADOW, });
A 3D tileset can be added by activating an asynchronous function and awaiting the tileset call:
const start = async function () { tileset = await Cesium.Cesium3DTileset.fromUrl('3dtiles/tileset.json?token=$TOKEN&style=$STYLE&spacing=$SPACING&texture=$TEXTURE'); viewer.scene.primitives.add(tileset); }
Once loaded, the camera can fly to the tileset by adding this after the tileset has been added to the scene (but before the end bracket of the start function)
boundingSphere = tileset.root.boundingVolume._boundingSphere viewer.camera.viewBoundingSphere(tileset.root.boundingVolume._boundingSphere); viewer.camera.flyToBoundingSphere(tileset.root.boundingVolume._boundingSphere);
A tileset can be updated with the following code
var tileseturl = new Cesium.Resource({ url: "3dtiles/tileset.json", queryParameters: { token: "$TOKEN" } }); tileseturl.fetchJson().then(data => { if (tilesetversion == null) { tilesetversion = data.asset.tilesetVersion; } else if (data.asset.tilesetVersion > tilesetversion) { tilesetversion = data.asset.tilesetVersion; var tilerequest = Cesium.Cesium3DTileset.fromUrl('3dtiles/tileset.json?token=$TOKEN&style=$STYLE&spacing=$SPACING&texture=$TEXTURE'); tilerequest.then((newtileset) => { viewer.scene.primitives.add(newtileset); tileset.show = false; viewer.scene.primitives.remove(tileset); tileset = newtileset; }); } });
Adding overlays to the Cesium viewer:
const provider = new Cesium.WebMapServiceImageryProvider({ url: 'wms', layers: overlayID, maximumLevel: maxLevel, tileHeight: tilepx, tileWidth: tilepx, proxy: new Cesium.DefaultProxy('/proxy/'), parameters: { crs: "4326", forcexy: "true", token: "$TOKEN", timeframe: timeframe, styles: difference ? STYLE_DIFFERENCE : "", version: version }, getFeatureInfoParameters: { crs: "4326", forcexy: "true", token: "$TOKEN", timeframe: timeframe, styles: difference ? STYLE_DIFFERENCE : "", version: version } }); viewer.imageryLayers.remove(overlayLayer); var newOverlayLayer = new Cesium.ImageryLayer(provider, { minimumTerrainLevel: minLevel }); viewer.imageryLayers.add(newOverlayLayer); overlayControl.setActiveOverlayLayer(newOverlayLayer); if (overlayLayer != null) { overlayLayer.destroy(); }
Variables
- $TOKEN = API token.
- $BGCOLOR = Hexa-color.
- $BASEMAP_INDEX = nominal; SATELLITE=0, TOPOGRAPHIC=1 and GRAY=2.
- $SHADOW = boolean.
- $SPACING = distance number.
- $TEXTURE = String value. Allowed: "SMALL", "MEDIUM" or "LARGE".
- $STYLE = String value. Allowed: "WHITE", "COLORED".