three-geo

three-geo

three-geo is a three.js based geographic visualization library. Using three-geo, we can easily build satellite-textured 3D terrain models in near real-time by simply specifying GPS coordinates anywhere on the globe. The geometry of the terrain is based on the RGB-encoded DEM (Digital Elevation Model) provided by the Mapbox Maps API.

The terrain is represented by standard THREE.Mesh objects. This makes it easy for us to access underlying geometry/texture array and perform original GIS (Geographic Information System) experiments in JavaScript. (See Usage for how to programatically obtain those mesh objects).

Credits: this library has been made possible thanks to

• geo-related libraries (mapbox, Turfjs) and the Mapbox Maps API.
• peterqliu for informative 3D terrain-related articles and implementation.

Demo

1) examples/geo-viewer (live | source code)

This demo app includes features such as

• on-demand 3D terrain building (by a mouse click on the Leaflet map),
• real-time camera projection onto Leaflet (with oritentaion and HFoV indication),
• terrain interaction with a VR-like laser beam,
• measuring Euclidean distances between terrain points,
• auto camera orbiting around the custom z-axis.

Live:

• https://w3reality.github.io/three-geo/examples/geo-viewer/io/index.html?lat=46.5763&lng=7.9904

  

• https://w3reality.github.io/three-geo/examples/geo-viewer/io/index.html?lat=46.5763&lng=7.9904&mode=contours

  

• https://w3reality.github.io/three-geo/examples/geo-viewer/io/index.html?lat=36.2058&lng=-112.4413

  

2) examples/heightmaps (live | source code)

This demo illustrates the relationship between a reconstructed 3D terrain and its underlying satellite/DEM tiles.

3) examples/flat (live | source code)

How to get a flattened view of the terrain by post-editing the underlying geometry.

4) examples/projection (live | source code)

How to register a new 3D object on top of the terrain based on its geographic location [latitude, longitude, elevation].

Setup

Installation

$ npm i three-geo

Loading

Script tag: use ThreeGeo after

<script src="dist/three-geo.min.js"></script>

ES6:

import ThreeGeo from 'dist/three-geo.esm.js';

Usage

Here is an example of how to build a geographic terrain located at GPS coordinates (46.5763, 7.9904) in a 5 km radius circle. The terrain's satellite zoom resolution is set to 12. (The highest zoom value supported is 17.)

For standalone tests, use examples/simple-viewer (source code).

For use with NodeJS, do enable this isNode option as well.

const tgeo = new ThreeGeo({
    tokenMapbox: '********', // <---- set your Mapbox API token here
});

const terrain = await tgeo.getTerrainRgb(
    [46.5763, 7.9904], // [lat, lng]
    5.0,               // radius of bounding circle (km)
    12);               // zoom resolution

const scene = new THREE.Scene();
scene.add(terrain);

const renderer = new THREE.WebGLRenderer({ canvas });
renderer.render(scene, camera);

Who is using three-geo?

• jet-wasp - Three-geo as A-Frame component (source code)
• locus-pocus - A webapp to visualise your area using three-geo

API

In this section, we list three-geo's public API methods, where origin, radius, and zoom are parameters common to them:

• origin Array<number> Center of the terrain represented as GPS coordinates [latitude, longitude].

• radius number Radius of the circle that fits the terrain.

• zoom number (integer) Satellite zoom resolution of the tiles in the terrain. Select from {11, 12, 13, 14, 15, 16, 17}, where 17 is the highest value supported. For a fixed radius, higher zoom resolution results in more tileset API calls.

ThreeGeo

• constructor(opts={})

  Create a ThreeGeo instance with parameters.

  • opts.tokenMapbox="" string Mapbox API token. This must be provided.

  • opts.unitsSide=1.0 number The side length of the square that fits the terrain in WebGL space.

  • opts.isNode=false boolean To use three-geo with NodeJS, you must explicitly set this option to true. [ Added in v1.4.5 ]

• async getTerrainRgb(origin, radius, zoom) [ Added in v1.4 ]

  Return a THREE.Group object that represents a 3D surface of the terrain.

  The group object contains an Array<THREE.Mesh> as .children. Each mesh corresponds to a partial geometry of the terrain textured with satellite images.

• async getTerrainVector(origin, radius, zoom) [ Added in v1.4 ]

  Return a THREE.Group object that represents a 3D contour map of the terrain.

  The group object contains an Array<THREE.Object3D> as .children. Each child object is either an extruded THREE.Mesh with .name attribute prefixed by dem-vec-shade-<ele>-, or a THREE.Line with .name prefixed by dem-vec-line-<ele>- (<ele> is the height of each contour in meters).

• getProjection(origin, radius, unitsSide=1.0) [ Example ]

  Return an object { proj, projInv, bbox, unitsPerMeter } that includes transformation-related functions and parameters, where

  • proj(latlng) is a function that maps geo coordinates latlng (an array [lat, lng]) to WebGL coordinates [x, y].

  • projInv(x, y) is a function that maps WebGL coordinates [x, y] to geo coordinates [lat, lng].

  • bbox is an array [w, s, e, n] that represents the computed bounding box of the terrain, where w (West) and e (East) are longitudinal limits; and s (South) and n (North) are latitudinal limits.

  • unitsPerMeter is the length in WebGL-space per meter.

Legacy callback based API

• getTerrain(origin, radius, zoom, callbacks={})

  • callbacks.onRgbDem function (meshes) {} Implement this to request the geometry of the terrain. Called when the entire terrain's geometry is obtained.

    • meshes Array<THREE.Mesh> All the meshes belonging to the terrain.

  • callbacks.onSatelliteMat function (mesh) {} Implement this to request the satellite textures of the terrain. Called when the satellite texture of each mesh belonging to the terrain is obtained.

    • mesh THREE.Mesh One of the meshes that's part of the terrain.

  • callbacks.onVectorDem function (objs) {} Implement this to request the contour map of the terrain. Called when the contour map of the terrain is obtained.

    • objs Array<THREE.Object3D> Extruded meshes (THREE.Mesh objects with .name attribute prefixed by dem-vec-shade-<ele>-) and lines (THREE.Line objects with .name attribute prefixed by dem-vec-line-<ele>-), where <ele> is the height of each contour in meters.

Build

$ npm i
$ npm run build