Animation Transitions

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

<Pane
  title="Transitions"
  position="fixed"
>
  <Button
    title="Idle"
    on:click={() => {
      $buttonIdle = !$buttonIdle
    }}
  />
  <Button
    title="Walk"
    on:click={() => {
      $buttonWalk = !$buttonWalk
    }}
  />
  <Button
    title="Run"
    on:click={() => {
      $buttonRun = !$buttonRun
    }}
  />
</Pane>

<div>
  <Canvas>
    <Scene />
  </Canvas>
</div>

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

<script lang="ts">
  import { onDestroy } from 'svelte'
  import { GLTF, useGltfAnimations } from '@threlte/extras'
  import { buttonIdle, buttonWalk, buttonRun } from './state'

  let currentActionKey = 'idle'

  const { gltf, actions } = useGltfAnimations()

  $: $actions[currentActionKey]?.play()

  const unsub1 = buttonIdle.subscribe(() => {
    console.log('transition to idle')
    transitionTo('idle', 0.3)
  })

  const unsub2 = buttonWalk.subscribe(() => {
    console.log('transition to run')
    transitionTo('walk', 0.3)
  })

  const unsub3 = buttonRun.subscribe(() => {
    console.log('transition to run')
    transitionTo('run', 0.3)
  })

  function transitionTo(nextActionKey: string, duration = 1) {
    const currentAction = $actions[currentActionKey]
    const nextAction = $actions[nextActionKey]
    if (!nextAction || currentAction === nextAction) return
    // Function inspired by: https://github.com/mrdoob/three.js/blob/master/examples/webgl_animation_skinning_blending.html
    nextAction.enabled = true
    if (currentAction) {
      currentAction.crossFadeTo(nextAction, duration, true)
    }
    // Not sure why I need this but the source code does not
    nextAction.play()
    currentActionKey = nextActionKey
  }

  onDestroy(() => {
    // We unsubscribe otherwise we'd have old subscriptions still active
    unsub1()
    unsub2()
    unsub3()
  })
</script>

<GLTF
  bind:gltf={$gltf}
  url="https://threejs.org/examples/models/gltf/Xbot.glb"
/>

<script lang="ts">
  import { T } from '@threlte/core'
  import { injectLookAtPlugin } from '../../plugins/lookAt/lookAtPlugin'
  import Character from './Character.svelte'

  injectLookAtPlugin()
</script>

<T.PerspectiveCamera
  makeDefault
  position={[-0.85, 1.75, 2.46]}
  lookAt={[0, 1, 0]}
/>

<T.AmbientLight />
<T.DirectionalLight position={[10, 5, 5]} />

<Character />

<T.Mesh rotation.x={-90 * (Math.PI / 180)}>
  <T.CircleGeometry args={[3, 72]} />
  <T.MeshStandardMaterial color={'white'} />
</T.Mesh>

import { writable } from 'svelte/store'

export const buttonIdle = writable(false)
export const buttonWalk = writable(false)
export const buttonRun = writable(false)