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" - "动画混合", "骨骼动画", "剪辑", "淡入淡出" ## 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](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](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](https://threejs.org/docs/#Animation) section of the [docs index](https://threejs.org/docs/) 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](https://threejs.org/docs/AnimationAction.html)). 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 **中文：** 动画混合、AnimationMixer、AnimationAction、关键帧、骨骼动画、剪辑、淡入淡出、three.js