3D vector tiles with Cesium

This article contains information about how to work with 3D vector tiles and Cesium.

Terrain modeling

3D terrain data can be represented in several ways. In the field of GIS, raster file images are usually used, and each cell value represents elevation (Digital Elevation Model).

For the purpose of visualisation of elevation model, another format can be used, so called Quantized 3D Mesh - the elevation is represented by either regular, but more commonly irregular triangle web.

Sources of 3D data

For the purpose of visualization of terrain in the web browser, is Cesium one of the popular JavaScript libraries and data services to be used. You can set up your web application for 3D data visualization in several ways:

• Have your own terrain data and convert them to 3D quantized mesh format - then you need a server to a) process the data and b) to serve them

• We at MapTiler do provide 3D tiles hosting service. If you login to your MaptTiler Cloud account, you can find 3D Terrain - Quantized Mesh tiles dataset there - and use it in your applications.

  

• Use data provided by the Cesium service

Having 3D tiles data source is only one part of the problem. The 3D tiles will help you just to draw the elevation, but one also needs to “drape” another data source over the elevation, such as the streets map, outdoor map or the satellite map. That way, you can see nice 3D shaped landscape.

Configuring Cesium map application

When building a web applications, you have several options and you probably know already, which libraries and build-stack you are going to use. You can find a lot of useful examples at the Sandcastle of the Cesium project. We will demonstrate, how to create 3D web mapping application based on the cesium-webpack-example

Step 1: Install and run minimal Cesium application using webpack

Webpack is the static module builder for JavaScript applications. It helps you with the development of the new application as well as with the creation of the distribution package.

Download and unzip the cesium-webpack-example package (either using the direct download link or using Git commands)

git clone https://github.com/maptiler/cesium-webpack-example.git
cd cesium-webpack-example

Then run the command, which should install all necessary dependencies

npm install

And after all necessary packages are successfully downloaded, you can start the development server, which will make it easy to develop a custom 3D mapping application

npm start

And open the link http://localhost:8080/ in your browser

Basic example with Cesium data sources will popup. Now let’s start hacking around this example. The sources are located in the src/ folder, the file src/index.js is of our main interest:

import { Cesium3DTileset, createWorldTerrain, IonResource, Viewer } from 'cesium';
import "cesium/Build/Cesium/Widgets/widgets.css";
import "./css/main.css";

var viewer = new Viewer('cesiumContainer', {
    terrainProvider: createWorldTerrain()
});

var tileset = new Cesium3DTileset({
    url: IonResource.fromAssetId(40866)
});

viewer.scene.primitives.add(tileset);
viewer.zoomTo(tileset);

We will restructure the code, so it uses sources directing to MapTiler cloud services. Let’s start from scratch, delete all the code, maybe except for the imports

import { Cesium3DTileset, createWorldTerrain, IonResource, Viewer } from 'cesium';
import "cesium/Build/Cesium/Widgets/widgets.css";
import "./css/main.css";

First we need to define the TerrainProvider instance

var terrain = new CesiumTerrainProvider({
  url: `https://api.maptiler.com/tiles/terrain-quantized-mesh/?key=${MAPTILER_API_KEY}`
});

As second step, we need to define the ImageProvider - and we will use the URL reference to one of the Maptiler services, in this case, it will be the Outdoor map:

var outdoor = new UrlTemplateImageryProvider({
  url: `https://api.maptiler.com/maps/outdoor/{z}/{x}/{y}.png?key=${MAPTILER_API_KEY}`,
  minimumLevel: 0,
  maximumLevel: 20
});

We now have to important data sources: the terrain and the imagery overlay. This can be now pluged-in to the application. This can be done, using very complex Cesium.Viewer class or much simplier Cesium.Widget class.

var cesiumWidget = new CesiumWidget('cesiumContainer', 
  {
    imageryProvider: outdoor,
    terrainProvider: terrain
  }
);

Don’t forget to add used classes, which is CesiumTerrainProvider, UrlTemplateImageryProvider and the CesiumWidget to the import statement. The node server will reload automatically every time you change the code.

Now we just have to zoom to desired location (e.g. Alps region), this is done with the help of the Camera object

viewer.camera.flyTo({
   destination: Cartesian3.fromDegrees(8.67, 46.72, 4300),
   orientation: { pitch: Math.toRadians(-20) }
});

The full example now looks like this:

import { Cesium3DTileset, createWorldTerrain, IonResource, CesiumTerrainProvider,
         UrlTemplateImageryProvider, Viewer, CesiumWidget, Cartesian3,
         Math } from 'cesium';
import "cesium/Build/Cesium/Widgets/widgets.css";
import "./css/main.css";

var MAPTILER_API_KEY="XFXXXXXXXXXXXXXeeg";

var terrain = new CesiumTerrainProvider({
  url: `https://api.maptiler.com/tiles/terrain-quantized-mesh/?key=${MAPTILER_API_KEY}`
});

var outdoor = new UrlTemplateImageryProvider({
  url: `https://api.maptiler.com/maps/outdoor/{z}/{x}/{y}.png?key=${MAPTILER_API_KEY}`,
  minimumLevel: 0,
  maximumLevel: 20
});

var widget = new CesiumWidget('cesiumContainer', 
  {
    imageryProvider: outdoor,
    terrainProvider: terrain
  }
);

widget.camera.flyTo({
   destination: Cartesian3.fromDegrees(8.67, 46.72, 4300),
   orientation: { pitch: Math.toRadians(-20) }
});