Utilities for using THREE.js on Expo
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README.md

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expo-three

Tools for using three.js to build native 3D experiences 💙

Installation

yarn add three expo-three

Usage

Import the library into your JavaScript file:

import ExpoTHREE from 'expo-three';

Get a global instance of three.js from expo-three:

import { THREE } from 'expo-three';

You can also import AR tools:

// This alias is useful cuz Expo.AR could collide.
import { AR as ThreeAR } from 'expo-three';

ExpoTHREE.AR is not the same as Expo.AR. Think of Expo.AR as a data provider for ExpoTHREE.AR to visualize.

Creating a Renderer

ExpoTHREE.Renderer({ gl: WebGLRenderingContext, width: number, height: number, pixelRatio: number, ...extras })

Given a gl from an Expo.GLView, return a THREE.WebGLRenderer that draws into it.

const renderer = new ExpoTHREE.Renderer(props);
or;
/// A legacy alias for the extended renderer
const renderer = ExpoTHREE.createRenderer(props);
// Now just code some three.js stuff and add it to this! :D

ExpoTHREE.loadAsync()

A function that will asynchronously load files based on their extension.

Notice: Remember to update your app.json to bundle obscure file types!

"packagerOpts": {
  "assetExts": [
    "dae",
    "obj",
    "mtl"
  ]
}

Props

Property Type Description
resource PossibleAsset The asset that will be parsed asynchornously
onProgress (xhr) => void A function that is called with an xhr event
assetProvider () => Promise<Expo.Asset> A function that is called whenever an unknown asset is requested
PossibleAsset Format

export type PossibleAsset = Expo.Asset | number | string | AssetFormat;

type PossibleAsset = number | string | Expo.Asset;
  • number: Static file reference require('./model.*')
  • Expo.Asset: Expo.Asset
  • string: A uri path to an asset

Returns

This returns many different things, based on the input file. For a more predictable return value you should use one of the more specific model loaders.

Example

A list of supported formats can be found here

const texture = await ExpoTHREE.loadAsync('https://www.google.com/images/branding/googlelogo/2x/googlelogo_color_272x92dp.png');

Loaders

Don't forget to add your extensions to expo.packagerOpts.assetExts in the app.json

loadAsync(assetReference, onProgress, onAssetRequested)

A universal loader that can be used to load images, models, scenes, and animations. Optionally more specific loaders are provided with less complexity.

// A THREE.Texture from a static resource.
const texture = await ExpoTHREE.loadAsync(require('./icon.png'));
const obj = await ExpoTHREE.loadAsync(
  [
    require('./cartman.obj'),
    require('./cartman.mtl')
  ],
  null,
  (imageName) => resources[imageName]
);
const { scene } = await ExpoTHREE.loadAsync(
  resources['./kenny.dae'],
  onProgress,
  resources
);

loadObjAsync({ asset, mtlAsset, materials, onAssetRequested, onMtlAssetRequested })

Props

  • asset: a obj model reference that will be evaluated using AssetUtils.uriAsync
  • mtlAsset: an optional prop that will be loaded using loadMtlAsync()
  • onAssetRequested: A callback that is used to evaluate urls found within the asset and optionally the mtlAsset. You can also just pass in a dictionary of key values if you know the assets required ahead of time.
  • materials: Optionally you can provide an array of materials returned from loadMtlAsync()
  • onMtlAssetRequested: If provided this will be used to request assets in loadMtlAsync()

This function is used as a more direct method to loading a .obj model. You should use this function to debug when your model has a corrupted format.

const mesh = await loadObjAsync({ asset: 'https://www.members.com/chef.obj' })

See: MTL Loader Demo

loadTextureAsync({ asset })

Props

  • asset: an Expo.Asset that could be evaluated using AssetUtils.resolveAsync if localUri is missing or the asset hasn't been downloaded yet.

This function is used as a more direct method to loading an image into a texture. You should use this function to debug when your image is using an odd extension like .bmp.

const texture = await loadTextureAsync({ asset: require('./image.png') })

loadMtlAsync({ asset, onAssetRequested })

Props

  • asset: a mtl material reference that will be evaluated using AssetUtils.uriAsync
  • onAssetRequested: A callback that is used to evaluate urls found within the asset, optionally you can just pass in a dictionary of key values if you know the assets required ahead of time.
const materials = await loadMtlAsync({
  asset: require('chef.mtl'),
  onAssetRequested:
  modelAssets
})

See: MTL Loader Demo

loadDaeAsync({ asset, onAssetRequested, onProgress })

Props

  • asset: a reference to a dae scene that will be evaluated using AssetUtils.uriAsync
  • onAssetRequested: A callback that is used to evaluate urls found within the asset, optionally you can just pass in a dictionary of key values if you know the assets required ahead of time.
  • onProgress: An experimental callback used to track loading progress.
const { scene } = await loadDaeAsync({
  asset: require('chef.dae'),
  onAssetRequested: modelAssets,
  onProgress: () => {}
})

See: Collada Loader Demo

AR

Tools and utilites for working with ARKit in Expo.

Here is an example of a basic AR enabled scene. Also in snack form!

import { AR } from 'expo';
import ExpoTHREE, { AR as ThreeAR, THREE } from 'expo-three';
import React from 'react';
import { View as GraphicsView } from 'expo-graphics';

export default class App extends React.Component {
  render() {
    // You need to add the `isArEnabled` & `arTrackingConfiguration` props.
    return (
      <GraphicsView
        style={{ flex: 2 }}
        onContextCreate={this.onContextCreate}
        onRender={this.onRender}
        onResize={this.onResize}
        isArEnabled
        isArRunningStateEnabled
        isArCameraStateEnabled
        arTrackingConfiguration={AR.TrackingConfigurations.World}
      />
    );
  }

  onContextCreate = ({ gl, scale: pixelRatio, width, height }) => {
    AR.setPlaneDetection(AR.PlaneDetectionTypes.Horizontal);

    this.renderer = new ExpoTHREE.Renderer({
      gl,
      pixelRatio,
      width,
      height,
    });

    this.scene = new THREE.Scene();
    this.scene.background = new ThreeAR.BackgroundTexture(this.renderer);
    this.camera = new ThreeAR.Camera(width, height, 0.01, 1000);
  };

  onResize = ({ x, y, scale, width, height }) => {
    this.camera.aspect = width / height;
    this.camera.updateProjectionMatrix();
    this.renderer.setPixelRatio(scale);
    this.renderer.setSize(width, height);
  };

  onRender = () => {
    this.renderer.render(this.scene, this.camera);
  };
}

Enabling AR:

  • Expo.GLView: call Expo.AR.startAsync(gl) after Expo.GLView.onContextCreate has been called.
  • expo-graphics: you need to add the isArEnabled & arTrackingConfiguration props.

new ExpoTHREE.AR.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 ExpoTHREE.AR.BackgroundTexture(renderer);

See: Basic Demo

new ExpoTHREE.AR.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 ExpoTHREE.AR.Camera(width, height, 0.01, 1000);

See: Basic Demo

new ExpoTHREE.AR.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 ExpoTHREE.AR.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 ExpoTHREE.AR.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 ExpoTHREE.AR.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 ExpoTHREE.AR.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 ExpoTHREE.AR.ShadowFloor({ width: 1, height: 1, opacity: 0.6 }); // The opacity of the shadow

See: Model Demo

new ExpoTHREE.AR.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 ExpoTHREE.AR.Points()

A utility object that renders all the raw feature points.

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

See: Points Demo

new ExpoTHREE.AR.Planes()

A utility object that renders all the ARPlaneAnchors

const planes = new ExpoTHREE.AR.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 ExpoTHREE.AR.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

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

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: Array

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 = false
  • dragOnInfinitePlanesEnabled = false
  • rawFeaturePoints = null

positionFromAnchor(anchor: ARAnchor): THREE.Vector3

Props

  • anchor: { worldTransform: Matrix4 }

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

Props

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

ExpoTHREE.utils

ExpoTHREE.utils.alignMesh()

Props

type Axis = {
  x?: number,
  y?: number,
  z?: number,
};
Property Type Description
mesh &THREE.Mesh The mesh that will be manipulated
axis ?Axis Set the relative center axis

Example

ExpoTHREE.utils.alignMesh(mesh, { x: 0.0, y: 0.5 });

ExpoTHREE.utils.scaleLongestSideToSize()

Props

Property Type Description
mesh &THREE.Mesh The mesh that will be manipulated
size number The size that the longest side of the mesh will be scaled to

Example

ExpoTHREE.utils.scaleLongestSideToSize(mesh, 3.2);

ExpoTHREE.utils.computeMeshNormals()

Used for smoothing imported geometry, specifically when imported from .obj models.

Props

Property Type Description
mesh &THREE.Mesh The mutable (inout) mesh that will be manipulated

Example

ExpoTHREE.utils.computeMeshNormals(mesh);
```

---

## THREE Extensions

### `suppressExpoWarnings`

A function that suppresses EXGL compatibility warnings and logs them instead.
You will need to import the `ExpoTHREE.THREE` global instance to use this. By
default this function will be activated on import.

* `shouldSuppress`: boolean

```js
import { THREE } from 'expo-three';
THREE.suppressExpoWarnings();

Links

Somewhat out of date