Getting started

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Giro3D - Getting started
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Welcome to Giro3D !
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In this tutorial, we will cover the base features of Giro3D : the creation of the instance, the creation of a map, and setting up the navigation controls.

Note

This walkthrough is based on the 2.5D Map example. Feel free to visit this example to see the final result of this tutorial.

import { Vector3 } from 'three';
import { MapControls } from 'three/examples/jsm/controls/MapControls.js';

import CoordinateSystem from '@giro3d/giro3d/core/geographic/CoordinateSystem.js';
import Extent from '@giro3d/giro3d/core/geographic/Extent.js';
import Instance from '@giro3d/giro3d/core/Instance.js';
import ColorLayer from '@giro3d/giro3d/core/layer/ColorLayer.js';
import ElevationLayer from '@giro3d/giro3d/core/layer/ElevationLayer.js';
import Map from '@giro3d/giro3d/entities/Map.js';
import BilFormat from '@giro3d/giro3d/formats/BilFormat.js';
import Inspector from '@giro3d/giro3d/gui/Inspector.js';
import WmsSource from '@giro3d/giro3d/sources/WmsSource.js';

import StatusBar from './widgets/StatusBar.js';

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Initialization of the Giro3D instance
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Before creating our map, we must setup Giro3D in our page, by creating an instance.

The instance is the entry point of a Giro3D context. It needs a DOM element to render its scene.

Register the custom CRS
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Our map uses the EPSG:3946 French coordinate reference system (CRS) that is not built-in into Giro3D’s CRS registry.

Let’s register a definition for this CRS. The definition is taken from https://epsg.io/3946.proj4.

const crs = CoordinateSystem.register(
    'EPSG:3946',
    '+proj=lcc +lat_1=45.25 +lat_2=46.75 +lat_0=46 +lon_0=3 +x_0=1700000 +y_0=5200000 +ellps=GRS80 +towgs84=0,0,0,0,0,0,0 +units=m +no_defs',
);

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Now we are ready to create our instance. Note that the crs parameter is necessary to determine the interpretation of coordinates from the 3D scene. We will use the view element from our HTML page to initialize the instance.
```
const instance = new Instance({
    target: 'view',
    crs,
});
```
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Create the Map
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Let’s create a map of the city of Lyon, with satellite imagery and a digital elevation model (DEM).

Specify the map extent
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A map is a rectangular region of the world that will contain geographic data.

Let’s define a geographic extent (or bounding box) of our map. We initialize the Extent class, specifying the CRS name (that we just defined above), with the minimum and maximum X (longitude, or easting) and Y (latitude, or northing) values.
```
const xmin = 1837816.94334;
const xmax = 1847692.32501;
const ymin = 5170036.4587;
const ymax = 5178412.82698;

const extent = new Extent(crs, xmin, xmax, ymin, ymax);
```
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Create the Map object
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Now we can create the Map. The only mandatory parameter is the extent but you can experiment with the other options if you’d like.
```
const map = new Map({ extent });
```
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Let’s add the map to the instance.
```
instance.add(map);
```
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Create the color layer
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If we looked at the page now, the map would be rendered as a colored rectangle. This is the aspect of the map without any data in it (only the background color). Nothing very exciting.

Let’s add a color layer.

In Giro3D, layers are the basic components of the Map. They can be either a color layer, or an elevation layer. In both cases, the data comes from a source.

Specify the data source

Let’s create a source that will pull data from a WMS service. We are using the WmsSource for that.

const satelliteSource = new WmsSource({
    url: 'https://data.geopf.fr/wms-r',
    projection: 'EPSG:3946',
    layer: 'ORTHOIMAGERY.ORTHOPHOTOS',
    imageFormat: 'image/jpeg',
});

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Create the layer
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Now we can create the layer. Note that we specify an extent for the layer. This is not strictly required, but since our map is much smaller than the WMS source, we want to avoid processing data that is outside our layer.
```
const colorLayer = new ColorLayer({
    name: 'satellite',
    source: satelliteSource,
    extent: map.extent,
});
```
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And add it to the map.
```
map.addLayer(colorLayer);
```
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Note: addLayer() is an asynchronous method, because the layer must be prepared before being ready for rendering. We could use the returned promise to wait for the end of the preprocessing step, but we don’t need that in our example.

Creation of the elevation layer
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Creating an elevation layer is a very similar process to the color layer : we initialize the source, then create the layer and add it to the map.

The only difference is that we are going to use an ElevationLayer.

Contrary to the color layer, the elevation layer does not produce any color information on the map, but it rather deforms the map to display the terrain (hence the name 2.5D map).

Let’s create a WMS source for this layer.
```
const demSource = new WmsSource({
    layer: 'ELEVATION.ELEVATIONGRIDCOVERAGE.HIGHRES',
    imageFormat: 'image/x-bil;bits=32',
    url: 'https://data.geopf.fr/wms-r',
    projection: 'EPSG:3946',
    format: new BilFormat(),
    noDataValue: -1000,
});
```
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Then create the elevation layer. We have set the resolution factor to 1/8th of the resolution of each map tile, because we are not going to display the pixels of the layer, but rather use the elevation data to deform the terrain mesh. Since the terrain mesh has a much lower resolution than the terrain textures, we don’t want to waste resources.
```
const elevationLayer = new ElevationLayer({
    name: 'dem',
    resolutionFactor: 1 / 8,
    extent: map.extent,
    source: demSource,
});
```
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Add the layer
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Now we are ready to add our layer to the map.
```
map.addLayer(elevationLayer);
```
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Set the camera and navigation controls
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Giro3D uses the THREE.js controls to navigate in the scene. In our example, we are going to use the MapControls, which are perfectly adapted to our need.

Let’s get the THREE camera of our scene.
```
const camera = instance.view.camera;
```

Let’s specify the camera position. We will position it in the southwest corner of the map, at an altitude of 2000 meters.

const cameraAltitude = 2000;

const cameraPosition = new Vector3(extent.minX, extent.minY, cameraAltitude);

camera.position.copy(cameraPosition);

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Now we can create the MapControls with our camera and the DOM element of our scene.
```
const controls = new MapControls(camera, instance.domElement);
```
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Let’s set the controls’ target to our map center.
```
controls.target = extent.centerAsVector3();
```

And specify some parameters for the navigation.

controls.enableDamping = true;
controls.dampingFactor = 0.2;
controls.maxPolarAngle = Math.PI / 2.3;

controls.saveState();

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Now let’s register those controls with the instance. The instance will automatically register the event handlers relevant to the navigation in the scene.
```
instance.view.setControls(controls);
```
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Optional: Set up the inspector
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This is an optional step, but very useful for diagnostic and debugging issues with Giro3D. The Inspector is a panel containing lots of useful information about the Giro3D instance.

This supposes that we have a div ready to host our inspector.
```
Inspector.attach('inspector', instance);
```
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The StatusBar
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This widget is no part of the Giro3D library, but is used in the examples to display various informations about the scene, such as the geographic coordinates of the mouse cursor.

Let’s initialize the coordinate bar widget on our instance.
```
StatusBar.bind(instance);
```
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Moving around
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Use the mouse the navigate in the scene and observe the map updating with fresh data.

See the final result.

Giro3D - Getting started

Welcome to Giro3D !

Note

Initialization of the Giro3D instance

Register the custom CRS

Create the Map

Specify the map extent

Create the Map object

Create the color layer

Specify the data source

Create the layer

Creation of the elevation layer

Add the layer

Set the camera and navigation controls

Optional: Set up the inspector

The StatusBar

Moving around