threejs-objects

## When to use this skill **ALWAYS use this skill when the user mentions:** - Parent/child relationships, `position/rotation/scale`, `matrixAutoUpdate`, `updateMatrixWorld` - Choosing mesh types: static vs instanced vs skinned vs batched LOD - **Picking**: `Raycaster.setFromCamera`, `intersectObjects`, recursive flag, face/uv results - **Layers**: selective visibility for cameras/lights/objects **IMPORTANT: objects vs math** | Need | Skill | |------|--------| | Scene graph + picking | **threejs-objects** | | Box/ray math only | **threejs-math** | **Trigger phrases include:** - "Object3D", "InstancedMesh", "SkinnedMesh", "Raycaster", "layers" - "父子节点", "射线拾取", "图层" ## How to use this skill 1. **Compose** scenes with `Group` and transforms; minimize deep hierarchies where possible. 2. **Instancing**: set per-instance matrices; understand `count` and frustum culling behavior. 3. **SkinnedMesh**: bind skeleton; clips in **threejs-animation**; skinning material flags in **threejs-materials**. 4. **Picking**: normalize device coords, set ray from camera, filter by layers, sort intersections. 5. **Events**: `EventDispatcher` on custom objects—patterns only, not DOM frameworks. 6. **Clipping**: `ClippingGroup` usage per docs when user needs sectional cuts. 7. **Dispose**: geometries/materials/textures when removing objects permanently. See [examples/workflow-raycaster-pick.md](examples/workflow-raycaster-pick.md). ## Doc map (official) | Docs section | Representative links | |--------------|----------------------| | Core | https://threejs.org/docs/Object3D.html | | Objects | https://threejs.org/docs/Mesh.html | | Objects | https://threejs.org/docs/InstancedMesh.html | | Core | https://threejs.org/docs/Raycaster.html | ## Scope - **In scope:** Object3D graph, renderable object types, raycasting, layers, dispatcher basics. - **Out of scope:** Physics engines; XR input mapping (**threejs-webxr**). ## Common pitfalls and best practices - Forgetting `updateMatrixWorld` before world-space ray tests on moved objects. - Raycaster without `layers` set picks unintended objects—set masks consistently on camera and objects. - InstancedMesh raycast hits need per-instance handling—check docs for your version. ## Documentation and version `Object3D`, mesh types, `Raycaster`, and `Layers` are documented under [Objects](https://threejs.org/docs/#Objects) and [Core](https://threejs.org/docs/Raycaster.html) in [three.js docs](https://threejs.org/docs/). Behavior of picking and layers can shift slightly—link the exact page for the user’s three.js line. ## Agent response checklist When answering under this skill, prefer responses that: 1. Link `Object3D`, `Mesh`, `InstancedMesh`, `Raycaster`, or `Layers` as needed. 2. Pair skeletal animation with **threejs-animation** and skinned mesh setup. 3. Route pure linear-algebra questions without a scene graph to **threejs-math**. 4. Route XR input to **threejs-webxr** when sessions/controllers are involved. 5. Mention `dispose()` for geometries/materials when removing objects permanently. ## References - https://threejs.org/docs/Object3D.html - https://threejs.org/docs/Raycaster.html - https://threejs.org/docs/Layers.html - https://threejs.org/docs/InstancedMesh.html ## Keywords **English:** object3d, mesh, instancedmesh, skinnedmesh, raycaster, layers, scene graph, three.js **中文：** 场景图、Object3D、Mesh、实例化、骨骼网格、射线拾取、图层、three.js