Pmndrs.docs

Hooks

Hooks are the heart of react-three-fiber

Hooks allow you to tie or request specific information to your component. For instance, components that want to participate in the renderloop can use useFrame, components that need to be informed of three.js specifics can use useThree and so on. All hooks clean up after themselves once the component unmounts.

Hooks can only be used inside the Canvas element because they rely on context!

โŒ You cannot expect something like this to work:

import { useThree } from '@react-three/fiber'

function App() {
  const { size } = useThree() // This will just crash
  return (
    <Canvas>
      <mesh>

โœ… Do this instead:

function Foo() {
  const { size } = useThree()

function App() {
  return (
    <Canvas>
      <Foo />

useThree

This hook gives you access to the state model which contains the default renderer, the scene, your camera, and so on. It also gives you the current size of the canvas in screen and viewport coordinates.

import { useThree } from '@react-three/fiber'

function Foo() {
  const state = useThree()

The hook is reactive, if you resize the browser for instance, you get fresh measurements, same applies to any of the state objects that may change.

State properties

PropDescriptionType
glRendererTHREE.WebGLRenderer
sceneSceneTHREE.Scene
cameraCameraTHREE.PerspectiveCamera
mouseContains updated, normalized, centric pointer coordinatesTHREE.Vector2
clockRunning system clockTHREE.Clock
vrTrue when the system is in VR modeboolean
linearTrue when the colorspace is linearboolean
flatTrue when no tonemapping is usedboolean
frameloopReact render-modealways, demand, never
performanceSystem regression{ current: number, min: number, max: number, debounce: number, regress: () => void }
sizeCanvas size in pixels{ width: number, height: number }
viewportViewport size in three.js units{ width: number, height: number, initialDpr: number, dpr: number, factor: number, distance: number, aspect: number, getCurrentViewport: (camera?: Camera, target?: THREE.Vector3, size?: Size) => Viewport }
setAllows you to set any state property(state: SetState<RootState>) => void
getAllows you to retrieve any state property non-reactively() => GetState<RootState>
invalidateRequest a new render, given that frameloop === 'demand'() => void
advanceAdvance one tick, given that frameloop === 'never'(timestamp: number, runGlobalEffects?: boolean) => void
setSizeResize the canvas(width: number, height: number) => void
setDprSet the pixel-ratio(dpr: number) => void
onPointerMissedResponse for pointer clicks that have missed a target() => void
eventsPointer-event handling{ connected: TargetNode, handlers: Events, connect: (target: TargetNode) => void, disconnect: () => void }

Selector

You can also select properties, this allows you to avoid needless re-render for components that are interested only in particulars. Reactivity does not include deeper three.js internals!

// Will only trigger re-render when the default camera is exchanged
const camera = useThree((state) => state.camera)
// Will only re-render on resize changes
const viewport = useThree((state) => state.viewport)
// โŒ You cannot expect reactivity from three.js internals!
const zoom = useThree((state) => state.camera.zoom)

Reading state from outside of the component cycle

function Foo() {
  const get = useThree((state) => state.get)
  ...
  get() // Get fresh state from anywhere you want

Exchanging defaults

function Foo() {
  const set = useThree((state) => state.set)
  ...
  useEffect(() => {
    set({ camera: new THREE.OrthographicCamera(...) })
  }, [])

useFrame

This hook allows you to execute code on every rendered frame, like running effects, updating controls, and so on. You receive the state (same as useThree) and a clock delta. Your callback function will be invoked just before a frame is rendered. When the component unmounts it is unsubscribed automatically from the render-loop.

import { useFrame } from '@react-three/fiber'

function Foo() {
  useFrame((state, delta) => {
    // This function runs 60 times/second inside the global render-loop
  })
Be careful about what you do inside useFrame! You should never setState in there! You calculations should be slim and you should mind all the commonly known pitfalls when dealing with loops in general, like re-use of variables, etc.

Taking over the render-loop

If you need more control you may pass a numerical renderPriority value. This will cause React Three Fiber to disable automatic rendering altogether. It will now be your responsibility to render, which is useful when you're working with effect composers, heads-up displays, etc.

function Render() {
  // Takes over the render-loop, the user has the responsibility to render
  useFrame(({ gl, scene, camera }) => {
    gl.render(scene, camera)
  }, 1)

function RenderOnTop() {
  // This will execute *after* Render's useframe
  useFrame(({ gl, ... }) => {
    gl.render(...)
  }, 2)
Callbacks will be executed in order of ascending priority values (lowest first, highest last.), similar to the DOM's z-order.

Negative indices

Using negative indices will not take over the render loop, but it can be useful if you really must order the sequence of useFrames across the component tree.

function A() {
  // This will execute first
  useFrame(() => ..., -1)

function B() {
  // This useFrame will execute *after* A's
  useFrame(() => ..., -2)

useLoader

This hook loads assets and suspends for easier fallback- and error-handling. It can take any three.js loader as its first argument: GLTFLoader, OBJLoader, TextureLoader, FontLoader, etc. It is based on React.Suspense, so fallback-handling and error-handling happen at the parental level.

import { Suspense } from 'react'
import { useLoader } from '@react-three/fiber'
import { GLTFLoader } from 'three/examples/jsm/loaders/GLTFLoader'

function Model() {
  const result = useLoader(GLTFLoader, '/model.glb')
  // You don't need to check for the presence of the result, when we're here
  // the result is guaranteed to be present since useLoader suspends the component
  return <primitive object={result.scene} />
}

function App() {
  return (
    <Suspense fallback={<FallbackComponent /> /* or null */}>
      <Model />
    </Suspense>
  )
}
Assets loaded with useLoader are cached by default. The urls given serve as cache-keys. This allows you to re-use loaded data everywhere in the component tree.
Be very careful with mutating or disposing of loaded assets, especially when you plan to re-use them. Refer to the automatic disposal section in the API.

Loader extensions

You can provide a callback as the third argument if you need to configure your loader:

import { DRACOLoader } from 'three/examples/jsm/loaders/DRACOLoader'

useLoader(GLTFLoader, url, (loader) => {
  const dracoLoader = new DRACOLoader()
  dracoLoader.setDecoderPath('/draco-gltf/')
  loader.setDRACOLoader(dracoLoader)
})

Loading multiple assets at once

It can also make multiple requests in parallel:

const [bumpMap, specMap, normalMap] = useLoader(TextureLoader, [url1, url2, url2])

Loading status

You can get the loading status from a callback you provide as the fourth argument. Though consider alternatives like THREE.DefaultLoadingManager or better yet, Drei's loading helpers.

useLoader(loader, url, extensions, xhr => {
  console.log((xhr.loaded / xhr.total * 100) + '% loaded')
}

Special treatment of GLTFLoaders and all loaders that return a scene prop

If a result.scene prop is found the hook will automatically create a object & material collection: { nodes, materials }. This lets you build immutable scene graphs selectively. You can also specifically alter the data without having to traverse it. GLTFJSX specifically relies on this data.

const { nodes, material } = useLoader(GLTFLoader, url)

Pre-loading assets

You can pre-load assets in global space so that models can be loaded in anticipation before they're mounted in the component tree.

useLoader.preload(GLTFLoader, '/model.glb' /* extensions */)

useGraph

Convenience hook which creates a memoized, named object/material collection from any Object3D.

import { useLoader } from '@react-three/fiber'

function Model(url) {
  const scene = useLoader(OBJLoader, url)
  const { nodes, materials } = useGraph(scene)
  return <mesh geometry={nodes.robot.geometry} material={materials.metal} />