expo-three-ar

Tools for using three.js to build native AR experiences with Expo. This library is iOS only.

This library is a side-project and should not be considered production ready

Installation

yarn add three expo-three-ar

Usage

Import the library into your JavaScript file:

import * as ThreeAR from 'expo-three-ar';

Enabling AR

• expo-gl: call AR.startAsync(gl) after GLView.onContextCreate has been called.
• expo-graphics: you need to add the isArEnabled={true} prop

new BackgroundTexture(renderer: WebGLRenderingContext)

extends a THREE.Texture that reflects the live video feed of the AR session. Usually this is set as the .background property of a THREE.Scene to render the video feed behind the scene's objects.

// viewport width/height & zNear/zFar
scene.background = new BackgroundTexture(renderer);

See: Basic Demo

new Camera(width: number, height: number, zNear: number, zFar: number)

extends a THREE.PerspectiveCamera that automatically updates its view and projection matrices to reflect the AR session camera. width, height specify the dimensions of the target viewport to render to and near, far specify the near and far clipping distances respectively. The THREE.PerspectiveCamera returned has its updateMatrixWorld and updateProjectionMatrix methods overriden to update to the AR session's state automatically. THREE.PerspectiveCamera that updates it's transform based on the device's orientation.

// viewport width/height & zNear/zFar
const camera = new Camera(width, height, 0.01, 1000);

See: Basic Demo

new Light()

THREE.PointLight that will update it's color and intensity based on ARKit's assumption of the room lighting.

renderer.physicallyCorrectLights = true;
renderer.toneMapping = THREE.ReinhardToneMapping;
 
const arPointLight = new Light();
arPointLight.position.y = 2;
scene.add(arPointLight);
 
// You should also add a Directional for shadows
const shadowLight = new THREE.DirectionalLight();
scene.add(shadowLight);
// If you would like to move the light (you would) then you will need to add the lights `target` to the scene.
// The shadowLight.position adjusts one side of the light vector, and the target.position represents the other.
scene.add(shadowLight.target);
 
...
// Call this every frame:
arPointLight.update()

See: Model Demo

new MagneticObject()

A THREE.Mesh that sticks to surfaces. Use this as a parent to models that you want to attach to surfaces.

const magneticObject = new MagneticObject();
magneticObject.maintainScale = false; // This will scale the mesh up/down to preserve it's size regardless of distance.
magneticObject.maintainRotation = true; // When true the mesh will orient itself to face the camera.
 
// screenCenter is a normalized value = { 0.5, 0.5 }
const screenCenter = new THREE.Vector2(0.5, 0.5);
...
 
// Call this every frame to update the position.
magneticObject.update(camera, screenCenter);

See: Model Demo

new ShadowFloor()

A transparent plane that extends THREE.Mesh and receives shadows from other meshes. This is used to render shadows on real world surfaces.

renderer.gammaInput = true;
renderer.gammaOutput = true;
renderer.shadowMap.enabled = true;
const shadowFloor = new ShadowFloor({
  width: 1,
  height: 1,
  opacity: 0.6,
}); // The opacity of the shadow

See: Model Demo

new CubeTexture()

Used to load in a texture cube or skybox.

• assetForDirection: This function will be called for each of the 6 directions.
  • ({ direction }): A direction string will be passed back looking for the corresponding image. You can send back: static resource, localUri, Expo.Asset, remote image url
• directions: The order that image will be requested in. The default value is: ['px', 'nx', 'py', 'ny', 'pz', 'nz']

Example:

const skybox = {
  nx: require('./nx.jpg'),
  ny: require('./ny.jpg'),
  nz: require('./nz.jpg'),
  px: require('./px.jpg'),
  py: require('./py.jpg'),
  pz: require('./pz.jpg'),
};
const cubeTexture = new CubeTexture();
await cubeTexture.loadAsync({
  assetForDirection: ({ direction }) => skybox[direction],
});
scene.background = cubeTexture;

new Points()

A utility object that renders all the raw feature points.

const points = new Points();
// Then call this each frame...
points.update();

See: Points Demo

new Planes()

A utility object that renders all the ARPlaneAnchors

const planes = new Planes();
// Then call this each frame...
planes.update();

See: Planes Demo

AR Functions

Three.js calculation utilites for working in ARKit. Most of these functions are used for calculating the surfaces. You should see if MagneticObject() has what you need before digging into these. You can also check out this example provided by Apple

hitTestWithFeatures(camera: THREE.Camera, point: THREE.Vector2, coneOpeningAngleInDegrees: number, minDistance: number, maxDistance: number, rawFeaturePoints: Array)

Props

• camera: THREE.Camera
• point: THREE.Vector2
• coneOpeningAngleInDegrees: number
• minDistance: number
• maxDistance: number
• rawFeaturePoints: Array<any>

hitTestWithPoint(camera: THREE.Camera, point: THREE.Vector2)

Props

• camera: THREE.Camera
• point: THREE.Vector2

unprojectPoint(camera: THREE.Camera, point: THREE.Vector2)

Props

• camera: THREE.Camera
• point: THREE.Vector2

hitTestRayFromScreenPos(camera: THREE.Camera, point: THREE.Vector2)

Props

• camera: THREE.Camera
• point: THREE.Vector2

hitTestFromOrigin(origin: THREE.Vector3, direction: THREE.Vector3, rawFeaturePoints: ?Array)

Props

• origin: THREE.Vector3
• direction: THREE.Vector3
• rawFeaturePoints: ?Array<any>

hitTestWithInfiniteHorizontalPlane(camera: THREE.Camera, point: Point, pointOnPlane: THREE.Vector3)

Props

• camera: THREE.Camera
• point: THREE.Vector2
• pointOnPlane: THREE.Vector3

rayIntersectionWithHorizontalPlane(rayOrigin: THREE.Vector3, direction: THREE.Vector3, planeY: number)

Props

• rayOrigin: THREE.Vector3
• direction: THREE.Vector3
• planeY: number

convertTransformArray(transform: Array): THREE.Matrix4

Props

• transform: number[]

positionFromTransform(transform: THREE.Matrix4): THREE.Vector3

Props

• transform: THREE.Matrix4

worldPositionFromScreenPosition(camera: THREE.Camera, position: THREE.Vector2, objectPos: THREE.Vector3, infinitePlane = false, dragOnInfinitePlanesEnabled = false, rawFeaturePoints = null): { worldPosition: THREE.Vector3, planeAnchor: ARPlaneAnchor, hitAPlane: boolean }

Props

• camera: THREE.Camera
• position: THREE.Vector2
• objectPos: THREE.Vector3
• infinitePlane: boolean = false
• dragOnInfinitePlanesEnabled: boolean = false
• rawFeaturePoints: any = null

positionFromAnchor(anchor: ARAnchor): THREE.Vector3

Props

• anchor: { worldTransform: Matrix4 }

improviseHitTest(point, camera: THREE.Camera): ?THREE.Vector3

Props

• point: THREE.Vector2
• camera: THREE.Camera