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