threejs-geometries

When to use this skill

ALWAYS use this skill when the user mentions:

• Building or modifying BufferGeometry, attributes, index buffers, draw ranges
• Instancing via InstancedBufferAttribute / InstancedMesh geometry side (threejs-objects for mesh wrapper)
• Extruding Shape along paths, TubeGeometry, LatheGeometry, ExtrudeGeometry
• Text or decal addon geometries

IMPORTANT: geometries vs math

• threejs-geometries = GPU-ready triangle data.
• threejs-math = Box3, Sphere, Ray tests without mesh topology.

Trigger phrases include:

• "BufferGeometry", "BufferAttribute", "ExtrudeGeometry", "Shape", "Curve"
• "Geometry", "BufferGeometry", "Extrude", "TextGeometry"

How to use this skill

1. Prefer built-in primitives when they fit before custom buffers.
2. For custom meshes: create BufferGeometry, set position, normal, uv, optional index; compute bounding volumes for culling.
3. For instancing attributes, align divisor/count with InstancedMesh patterns in threejs-objects.
4. For 2D profiles: build Shape/Path, extrude or lathe per docs; consult Extras Curve family for path sampling.
5. For addon NURBS knots, follow Addons Curves pages sparingly—cite docs instead of copying full APIs.
6. Dispose geometries when replacing meshes to avoid leaks.

See examples/workflow-extrude-shape.md.

Doc map (official)

Docs section	Representative links
Core	https://threejs.org/docs/BufferGeometry.html
Geometries	https://threejs.org/docs/BoxGeometry.html
Extrude	https://threejs.org/docs/ExtrudeGeometry.html
Shape	https://threejs.org/docs/Shape.html

Scope

• In scope: Core geometries, buffer core, curve/shape/extrusion workflows, selected addon geometries.
• Out of scope: Physics collision mesh baking; full CAD import pipelines.

Common pitfalls and best practices

• Missing normals break lighting; compute or import consistently.
• Wrong winding order flips faces—check side/culling.
• Huge attribute counts need LOD or simplification (modifiers in addons—mention only if user asks).

Documentation and version

Primitives and BufferGeometry live under Geometries and BufferGeometry in three.js docs. Curve, Shape, and extrusion APIs appear under Extras and Geometries—Addons Curves / Geometries document NURBS and text meshes; link those instead of copying long signatures.

Agent response checklist

When answering under this skill, prefer responses that:

1. Link BufferGeometry, a primitive, or ExtrudeGeometry / Shape as appropriate.
2. Point instancing usage to threejs-objects for InstancedMesh patterns.
3. Point morph targets and tracks to threejs-animation when deformation is time-driven.
4. Reference BufferGeometryUtils (Addons Utils) only by name + docs link when merging/splitting.
5. Emphasize dispose() when replacing large custom buffers.

References

• https://threejs.org/docs/#Geometries
• https://threejs.org/docs/BufferGeometry.html
• https://threejs.org/docs/ExtrudeGeometry.html

Keywords

English: buffergeometry, extrude, shape, path, curve, primitives, instancing, three.js

Chinese: Geometry, BufferGeometry, Extrude, Shape, Curve, Instanced, three.js