@threlte/extras

useGltfAnimations

A convenience hook to use gltf animations loaded by a <GLTF> component or by the useGltf hook.

<script lang="ts">
  import Scene from './Scene.svelte'
  import { Button, Folder, Pane } from 'svelte-tweakpane-ui'
  import { Canvas } from '@threlte/core'

  let scene = $state.raw<Scene>()
  let animating = $state(false)

  const actions = $derived(scene?.actions)
  const action = $derived($actions?.['Take 001'])

  // start animating as soon as the action is ready
  $effect(() => {
    action?.play()
    animating = true
  })
</script>

<Pane
  position="fixed"
  title="littlest tokyo"
>
  <Folder title="animation">
    <Button
      disabled={animating}
      on:click={() => {
        action?.play()
        animating = true
      }}
      title="play"
    />
    <Button
      disabled={!animating}
      on:click={() => {
        action?.stop()
        animating = false
      }}
      title="stop"
    />
    <Button
      disabled={!animating}
      on:click={() => {
        action?.reset()
      }}
      title="reset"
    />
  </Folder>
</Pane>

<div>
  <Canvas>
    <Scene bind:this={scene} />
  </Canvas>
</div>

<style>
  div {
    height: 100%;
  }
</style>

<script lang="ts">
  import { Environment, OrbitControls, useDraco, useGltf, useGltfAnimations } from '@threlte/extras'
  import { T } from '@threlte/core'

  const dracoLoader = useDraco()
  const gltf = useGltf('/models/LittlestTokyo.glb', { dracoLoader })

  export const { actions, mixer } = useGltfAnimations<'Take 001'>(() => $gltf)
</script>

<T.PerspectiveCamera
  makeDefault
  position={[600, 200, -600]}
  near={10}
  far={10_000}
>
  <OrbitControls
    autoRotate
    autoRotateSpeed={0.2}
    enableDamping
    enableZoom={false}
    target={[-60, -75, 0]}
  />
</T.PerspectiveCamera>

<Environment
  url="/textures/equirectangular/hdr/industrial_sunset_puresky_1k.hdr"
  isBackground
/>

{#await gltf then { scene }}
  <T is={scene} />
{/await}

Model: Littlest Tokyo by Glen Fox, CC Attribution.

Examples

useGltfAnimations takes the gltf as a getter so that reads are tracked through runes automatically. The hook returns the mixer and an actions store keyed by clip name — type the clip names with a generic to get autocompletion.

With the `<GLTF>` component

Bind a local $state variable to the <GLTF> component’s gltf prop and pass the getter to useGltfAnimations.

<script lang="ts">
  import { GLTF, useGltfAnimations, type ThrelteGltf } from '@threlte/extras'

  let gltf = $state<ThrelteGltf>()
  const { actions, mixer } = useGltfAnimations<'All Animations'>(() => gltf)
  mixer.timeScale = 0.5

  $effect(() => {
    $actions['All Animations']?.play()
  })
</script>

<GLTF
  url="/path/to/model.glb"
  bind:gltf
/>

With the `useGltf` hook

When you want to reuse parts of the GLTF such as materials, nodes, or the embedded camera, load it with useGltf and pass the value through the getter.

<script lang="ts">
  import { T } from '@threlte/core'
  import { useGltfAnimations, useGltf } from '@threlte/extras'

  const gltf = useGltf('/path/to/model.glb')
  const { actions, mixer } = useGltfAnimations<'All Animations'>(() => $gltf)

  $effect(() => {
    $actions['All Animations']?.play()
  })
</script>

{#await gltf then { scene }}
  <T is={scene} />
{/await}

Applying Animations to a Different Root

useGltfAnimations’s second optional argument is a getter for an alternative root Object3D. Use this when you want to retarget the clips onto a separate rig rather than the gltf’s own scene.

<script lang="ts">
  import { T } from '@threlte/core'
  import { useGltfAnimations, useGltf } from '@threlte/extras'
  import { Group } from 'three'

  const gltf = useGltf('/path/to/model.glb')

  const group = new Group()

  const { actions } = useGltfAnimations(
    () => $gltf,
    () => group
  )
</script>

{#await gltf then { scene }}
  <T is={group}>
    <T is={scene} />
  </T>
{/await}

Previous Page useGltf

Next Page useTexture