Hooks

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.

❌ 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>

✅ Do this instead:

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

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

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.

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)
// ❌ You cannot expect reactivity from three.js internals!
const zoom = useThree((state) => state.camera.zoom)

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

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

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, xrFrame) => {
    // This function runs at the native refresh rate inside of a shared 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)

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(() => ..., -2)

function B() {
  // This useFrame will execute *after* A's
  useFrame(() => ..., -1)

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>
  )
}

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)
})

It can also make multiple requests in parallel:

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

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')
})

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, materials } = useLoader(GLTFLoader, url)

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 */)

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

import { useLoader, useGraph } 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} />
}