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id: wiki-2026-0508-buffergeometry
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title: BufferGeometry
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category: 10_Wiki/Topics
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status: verified
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canonical_id: self
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aliases: [P-Reinforce-AUTO-2887C6, Three.js BufferGeometry]
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duplicate_of: none
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source_trust_level: A
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confidence_score: 0.9
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verification_status: applied
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tags: [graphics, threejs, webgl, performance]
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raw_sources: []
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last_reinforced: 2026-05-10
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github_commit: pending
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tech_stack:
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language: javascript
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framework: three.js
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---
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# BufferGeometry
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## 매 한 줄
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> **"매 Three.js 의 GPU-resident geometry container — 매 modern Three 의 only geometry class."**. BufferGeometry 는 typed-array 기반 attribute (position, normal, uv, index) 의 GPU upload 를 직접 관리하며, 매 Geometry class deprecation (r125) 이후 표준 — instancing/batching/morph 의 backbone.
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## 매 핵심
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### 매 Attribute
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- **Position** (Float32Array, itemSize=3): vertex coords.
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- **Normal** (Float32Array, itemSize=3).
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- **UV** (Float32Array, itemSize=2).
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- **Index** (Uint16/Uint32Array): triangle list.
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- **Custom**: any vertex attribute (color, tangent, instance data).
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### 매 Update Strategy
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- **Static**: upload once, never modify (default).
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- **Dynamic** (`setUsage(DynamicDrawUsage)`): frequent CPU update.
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- **Stream**: per-frame update (rare).
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### 매 응용
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1. Custom shaders with custom attributes.
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2. GPU instancing (InstancedBufferAttribute).
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3. Procedural geometry generation.
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4. Mesh deformation / morphing.
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5. GPGPU particle systems.
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## 💻 패턴
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### Manual Triangle
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```javascript
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import * as THREE from "three";
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const geo = new THREE.BufferGeometry();
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const positions = new Float32Array([
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0, 1, 0,
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-1, -1, 0,
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1, -1, 0,
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]);
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geo.setAttribute("position", new THREE.BufferAttribute(positions, 3));
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geo.computeVertexNormals();
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```
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### Indexed Quad
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```javascript
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const positions = new Float32Array([-1,-1,0, 1,-1,0, 1,1,0, -1,1,0]);
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const indices = new Uint16Array([0, 1, 2, 0, 2, 3]);
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const geo = new THREE.BufferGeometry();
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geo.setAttribute("position", new THREE.BufferAttribute(positions, 3));
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geo.setIndex(new THREE.BufferAttribute(indices, 1));
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```
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### Dynamic Vertex Update
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```javascript
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const attr = geo.attributes.position;
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attr.setUsage(THREE.DynamicDrawUsage);
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function tick(t) {
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for (let i = 0; i < attr.count; i++) {
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attr.setY(i, Math.sin(t + i * 0.1));
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}
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attr.needsUpdate = true;
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}
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```
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### Custom Shader Attribute
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```javascript
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const aRandom = new Float32Array(geo.attributes.position.count);
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for (let i = 0; i < aRandom.length; i++) aRandom[i] = Math.random();
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geo.setAttribute("aRandom", new THREE.BufferAttribute(aRandom, 1));
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const mat = new THREE.ShaderMaterial({
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vertexShader: `attribute float aRandom; varying float vR;
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void main(){ vR=aRandom; gl_Position=projectionMatrix*modelViewMatrix*vec4(position,1.); }`,
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fragmentShader: `varying float vR; void main(){ gl_FragColor=vec4(vR,vR,vR,1.); }`,
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});
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```
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### Instanced Attribute
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```javascript
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const N = 10000;
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const offsets = new Float32Array(N * 3);
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for (let i = 0; i < N; i++) {
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offsets[i*3] = (Math.random()-0.5)*100;
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offsets[i*3+1] = (Math.random()-0.5)*100;
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offsets[i*3+2] = (Math.random()-0.5)*100;
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}
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const igeo = new THREE.InstancedBufferGeometry().copy(geo);
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igeo.instanceCount = N;
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igeo.setAttribute("aOffset", new THREE.InstancedBufferAttribute(offsets, 3));
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```
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### Merge Geometries
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```javascript
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import { mergeGeometries } from "three/addons/utils/BufferGeometryUtils.js";
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const merged = mergeGeometries([geoA, geoB, geoC], false);
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// single draw call instead of three
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```
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### Bounding Volume Recompute
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```javascript
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geo.computeBoundingBox();
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geo.computeBoundingSphere(); // required for frustum culling after vertex moves
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```
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## 매 결정 기준
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| 상황 | Approach |
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|---|---|
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| Static mesh | StaticDrawUsage (default) |
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| Per-frame deform | DynamicDrawUsage + needsUpdate |
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| Many copies | InstancedBufferGeometry |
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| Many distinct meshes | mergeGeometries or BatchedMesh |
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| Massive points | BufferGeometry + Points + custom shader |
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**기본값**: static indexed BufferGeometry; switch to instanced/merged for >100 copies.
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## 🔗 Graph
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- 부모: [[Three.js]]
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- 변형: [[BatchedMesh]]
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- Adjacent: [[BufferAttribute]]
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## 🤖 LLM 활용
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**언제**: generate procedural geometry boilerplate, debug attribute layout.
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**언제 X**: micro-optimization of custom shaders without profiling.
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## ❌ 안티패턴
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- **Forgetting `needsUpdate = true`**: GPU never re-uploads.
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- **Recreating BufferGeometry per frame**: GC pressure — mutate in place.
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- **Float32 indices**: not supported — use Uint16/Uint32.
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- **No bounding sphere recompute**: frustum-culled erroneously after deform.
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## 🧪 검증 / 중복
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- Verified (three.js r170 docs, threejs-journey).
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- 신뢰도 A.
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## 🕓 Changelog
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| 날짜 | 변경 |
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|---|---|
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| 2026-05-08 | Phase 1 |
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| 2026-05-10 | Manual cleanup — attributes, dynamic update, instancing patterns |
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