No Hips.position track of type VectorKeyframeTrack found in

Error message

No Hips.position track of type VectorKeyframeTrack found in animation.

What it means

After finding the hips node, reAnchorRootPositionTrack() searches clip.tracks for a VectorKeyframeTrack whose name is exactly `${hipNode.name}.position`. If no such track exists — the animation contains only rotations, or the position track uses a different PropertyBinding name/path — it warns and returns, leaving the root position uncorrected.

Source

Thrown at packages/stage-ui-three/src/composables/vrm/animation.ts:68

// Set initial positions for animation
export function reAnchorRootPositionTrack(clip: AnimationClip, _vrm: VRMCore) {
// Get the hips node to re-anchor the root position track
  const hipNode = _vrm.humanoid?.getNormalizedBoneNode('hips')
  if (!hipNode) {
    console.warn('No hips node found in VRM model.')
    return
  }
  hipNode.updateMatrixWorld(true)
  const defaultHipPos = new Vector3()
  hipNode.getWorldPosition(defaultHipPos)

  // Calculate the offset from the hips node to the hips's first frame position
  const hipsTrack = clip.tracks.find(track =>
    track instanceof VectorKeyframeTrack
    && track.name === `${hipNode.name}.position`,
  )
  if (!(hipsTrack instanceof VectorKeyframeTrack)) {
    console.warn('No Hips.position track of type VectorKeyframeTrack found in animation.')
    return
  }

  const animeHipPos = new Vector3(
    hipsTrack.values[0],
    hipsTrack.values[1],
    hipsTrack.values[2],
  )
  const animeDelta = new Vector3().subVectors(animeHipPos, defaultHipPos)

  clip.tracks.forEach((track) => {
    if (track.name.endsWith('.position') && track instanceof VectorKeyframeTrack) {
      for (let i = 0; i < track.values.length; i += 3) {
        track.values[i] -= animeDelta.x
        track.values[i + 1] -= animeDelta.y
        track.values[i + 2] -= animeDelta.z
      }
    }

View on GitHub (pinned to 677329427f)

Solutions

Log clip.tracks.map(t => t.name) and compare with the expected `${hipNode.name}.position` binding.
Use a .vrma that actually keyframes hips translation (full-body animations do).
If the track is optional for your clip type, guard with the same check and skip re-anchoring intentionally.

Example fix

// before
reAnchorRootPositionTrack(clip, vrm) // warns: no hips position track

// after
const hips = vrm.humanoid?.getNormalizedBoneNode('hips')
const hasHipsPos = !!hips && clip.tracks.some(t => t.name === `${hips.name}.position`)
if (hasHipsPos) reAnchorRootPositionTrack(clip, vrm)

Defensive patterns

Strategy: validation

Validate before calling

const hips = vrm.humanoid?.getNormalizedBoneNode('hips')
const hasHipsPosTrack = !!hips && clip.tracks.some(t => t.name === `${hips.name}.position`)
if (!hasHipsPosTrack) { /* rotation-only clip: skip re-anchor */ }

Prevention

Classify clips (full-body vs upper-body) before applying root re-anchoring.
Log track names when integrating new .vrma assets to confirm binding format.
Remember re-anchoring is an enhancement; design playback to be correct without it.

When it happens

Trigger: Playing an upper-body or idle .vrma that animates only bone quaternion tracks; a clip whose hips position track is bound to the raw (non-normalized) bone name so the normalized hipNode.name does not match; hand-built AnimationClips without a hips position track.

Common situations: Mix-and-match of clips from different rigs; three.js track-name formats (node.position vs bones[name].position) after retargeting; upper-body-only animations.

Related errors

AI-assisted analysis of moeru-ai/airi@677329427f (2026-08-18). Data as JSON: /api/errors/ff500c36eb7f5cce. Report an issue: GitHub.