<< User Guide

Viewing CityJSON using CityJSONLoader

How to load a CityJSON model directly into a xeokit web viewer.
Click on the preview below to run the example. Scroll down to learn how it's made.

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Viewing CityJSON using CityJSONLoader


HTML

Listed below is the HTML for this example.


<!doctype html>
<html>
<head>
    <meta charset="utf-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1">
    <meta name="viewport" content="width=device-width, initial-scale=1">
    <title>Viewing CityJSON using CityJSONLoader</title>
    <style>
        body {
            background-color: white;
            overflow: hidden;
            margin: 0;
            user-select: none;
        }

        #demoCanvas {
            width: 100%;
            height: 100%;
            position: absolute;
            background: white;
            border: 0;
        }
    </style>
</head>
<body>
<canvas id="demoCanvas"></canvas>
</body>
<script type="module" src="./index.js"></script>
</html>

JavaScript

Listed below is the JavaScript for this example, which we'll break down into steps.

1. Import the SDK from a bundle built for these examples.

import * as xeokit from "../../js/xeokit-demo-bundle.js";

2. Create a helper that sets up the Scene , Data, Viewer, and WebGLRenderer used by this demo.

import {DemoHelper} from "../../js/DemoHelper.js";
const demoHelper = new DemoHelper({});
demoHelper.init().then(({
                          scene,
                          data,
                          viewer,
                          view,
                          renderer
                        }) => {

3. Create a CityJSONLoader to load CityJSON files

  const cityJSONLoader = new xeokit.formats.cityjson.CityJSONLoader();

4. Configure the View 's World-space coordinate axis to make the +Z axis "up. This is actually the default, but we show it here for clarity

  view.camera.worldAxis = [
    1, 0, 0, // Right +X
    0, 0, 1, // Up +Z
    0, -1, 0  // Forward -Y
  ];

5. Arrange the View's Camera within our +Z "up" coordinate system

  view.camera.eye = [11.50, 16.32, 15.12];
  view.camera.look = [9.01, 9.65, 11.22];
  view.camera.up = [-0.16, -0.45, 0.87];
  view.camera.zoom(-15)

6. Create a SceneModel to hold our model's geometry and materials

  const sceneModelResult = scene.createModel({
    id: "demoModel",

7. coordinateSystem: { // Model's local CityJSON-standard coordinate system basis: [ 1, 0, 0, // Right +X 0, 0, 1, // Up +Z 0, -1, 0 // Forward -Y ], origin: [0, 0, 0], units: "meters" }

  });
  if (!sceneModelResult.ok) {
    return;
  }
  const sceneModel = sceneModelResult.value;

8. Create a DataModel to hold semantic data for our model

  const dataModelResult = data.createModel({
    id: "demoModel"
  });
  if (!dataModelResult.ok) {
    return;
  }
  const dataModel = dataModelResult.value;

9. Use CityJSONLoader to load an IFC model from a dotbim file into our SceneModel and DataModel

  fetch("../../models/LoD3_Railway/cityjson/model.json").then(response => {
    response
      .json()
      .then(fileData => {
        cityJSONLoader.load({
          fileData,
          sceneModel,
          dataModel
        }).then(() => {

10. The Scene and SceneModel will now contain a SceneObject for each displayable object in our model. The Data and DataModel will contain a DataObject for each IFC element in the model. Each SceneObject will have a corresponding DataObject with the same ID, to attach semantic meaning. The View will contain a ViewObject corresponding to each SceneObject, through which the appearance of the object can be controlled in the View.

          demoHelper.finished();
        }).catch(message => {
          console.error(`Error loading CityJSON: ${message}`);
        });
      });
  });
});