threejs-math

## When to use this skill **ALWAYS use this skill when the user mentions:** - Vector/matrix math order, `applyQuaternion`, `lookAt`, world vs local transforms - Bounding volumes `Box3`/`Sphere`, containment/intersection tests - `Ray` vs `Plane` vs `Frustum` tests (without full picking pipeline) **IMPORTANT: math vs objects vs animation** | Need | Skill | |------|--------| | Raw math types | **threejs-math** | | `Raycaster` + layers picking | **threejs-objects** | | QuaternionKeyframeTrack playback | **threejs-animation** | **Trigger phrases include:** - "Vector3", "Matrix4", "Quaternion", "Box3", "Ray", "Frustum" - "向量", "矩阵", "四元数", "包围盒" ## How to use this skill 1. **Conventions**: multiply vectors by matrices on the left as three.js examples show; call `updateMatrixWorld` before world-space queries (**threejs-objects**). 2. **Bounding**: `Box3().setFromObject(object)` for rough bounds; refine per need. 3. **Collision-ish checks**: `ray.intersectBox`, `sphere.containsPoint`, etc., per docs. 4. **Addon structures**: `Octree`/`OBB` for games—cite addon pages, avoid copying full API tables here. 5. **Color**: `Color` conversions relate to materials/textures—cross-link. 6. **Random sampling**: `MeshSurfaceSampler` for distributing points on meshes. See [examples/workflow-ray-aabb.md](examples/workflow-ray-aabb.md). ## Doc map (official) | Docs section | Representative links | |--------------|----------------------| | Math | https://threejs.org/docs/Vector3.html | | Math | https://threejs.org/docs/Matrix4.html | | Math | https://threejs.org/docs/Quaternion.html | | Math | https://threejs.org/docs/Ray.html | ## Scope - **In scope:** Core Math types; addon math entries as pointers. - **Out of scope:** Keyframe track evaluation beyond type references (animation skill). ## Common pitfalls and best practices - Euler gimbal lock—prefer quaternions for arbitrary rotations. - Reusing temporary vectors reduces GC thrash in hot loops. - Frustum culling helpers vary—verify against your three version. ## Documentation and version Core math types are listed under [Math](https://threejs.org/docs/#Math); addon utilities (`Octree`, `OBB`, …) appear under **Addons → Math** in [three.js docs](https://threejs.org/docs/). [Global](https://threejs.org/docs/#Global) also lists constants (e.g. wrapping, blending) sometimes needed alongside materials. ## Agent response checklist When answering under this skill, prefer responses that: 1. Link the concrete type (`Vector3`, `Matrix4`, `Quaternion`, …) from the docs. 2. Send `AnimationMixer` / track math to **threejs-animation** when time-sampled. 3. Send `Raycaster` picking flows to **threejs-objects** when interaction is the goal. 4. Mention numeric stability (epsilon) where comparisons matter. 5. Point to **Addons → Math** for game-oriented structures when users need spatial acceleration. ## References - https://threejs.org/docs/#Math - https://threejs.org/docs/MathUtils.html - https://threejs.org/docs/Ray.html ## Keywords **English:** vector, matrix, quaternion, euler, box3, sphere, ray, frustum, three.js **中文：** 向量、矩阵、四元数、欧拉角、包围盒、射线、three.js