threejs-animation

When to use this skill

ALWAYS use this skill when the user mentions:

• AnimationMixer.update, AnimationAction play/pause/stop, crossfade, synchronized clips
• AnimationClip from glTF or AnimationClipCreator, retargeting caveats at API level
• Keyframe tracks: position/rotation/scale/color tracks, boolean/string tracks where applicable
• IK: CCDIKSolver / CCDIKHelper from addons

IMPORTANT: animation vs objects

• threejs-animation = time evaluation and tracks.
• threejs-objects = SkinnedMesh/Skeleton attachment, bind pose—mesh side.

Trigger phrases include:

• "AnimationMixer", "AnimationAction", "AnimationClip", "crossFade", "KeyframeTrack"
• "Animation blending", "skeletal animation", "clips", "crossfading"

How to use this skill

1. Collect clips from gltf.animations or create with utilities / AnimationClipCreator.
2. Create mixer bound to root object (often scene or rig root).
3. Create actions per clip via mixer.clipAction(clip); configure loop mode (LoopOnce, LoopRepeat, LoopPingPong).
4. Per frame: compute delta seconds (use Clock from core—documented under Core in docs index), call mixer.update(delta).
5. Blending: adjust weight, crossFadeTo, enabled flags; watch for additive vs full replacement semantics per docs.
6. PropertyBinding: understand path strings targeting bones/morphs—errors often from wrong object names.
7. IK addon: attach solver after base animation if using CCD IK from examples.

See examples/workflow-mixer-action.md.

Doc map (official)

Docs section	Representative links
Animation (index)	https://threejs.org/docs/#Animation
Action	https://threejs.org/docs/AnimationAction.html
Mixer	https://threejs.org/docs/AnimationMixer.html
Clip	https://threejs.org/docs/AnimationClip.html
Tracks	https://threejs.org/docs/KeyframeTrack.html

More: references/official-sections.md.

Scope

• In scope: Core Animation module, keyframe pipeline, listed addons for clip creation and IK.
• Out of scope: DCC export best practices; physics ragdoll; audio sync (link conceptually only).

Common pitfalls and best practices

• Forgetting mixer.update freezes animation; double update per frame speeds up.
• Mixing clips with incompatible hierarchies causes violent pops—validate bind pose.
• Root motion must be handled in game logic if not baked—document explicitly.
• Large track counts cost CPU—strip unused tracks in preprocessing when possible.

Documentation and version

Behavior of AnimationMixer, tracks, and glTF animation import can change between three.js majors. Treat the Animation section of the docs index as authoritative for the user’s installed version; when upgrading, check the three.js repository release notes and migration notes for renamed properties or loader output.

Agent response checklist

When answering under this skill, prefer responses that:

1. Cite the exact class (AnimationMixer, AnimationAction, etc.) or addon (CCDIKSolver) from the official docs.
2. Include at least one https://threejs.org/docs/... link (e.g. AnimationAction).
3. Relate clips to SkinnedMesh / skeleton via threejs-objects when deformation is involved.
4. Mention mixer.update(delta) and a stable time source (Clock) explicitly.
5. Reference official examples by name only (no full file paste).

References

• https://threejs.org/docs/#Animation
• https://threejs.org/docs/AnimationMixer.html
• https://threejs.org/docs/AnimationAction.html
• https://threejs.org/docs/PropertyBinding.html

Keywords

English: animationmixer, animationaction, animationclip, keyframetrack, crossfade, skinning, propertybinding, three.js

Chinese: Animation blending, AnimationMixer, AnimationAction, keyframes, skeletal animation, clips, crossfading, three.js