2nd/10_Wiki/Topics/DevOps_and_Security/SkinnedMesh.md

---
id: wiki-2026-0508-skinnedmesh
title: SkinnedMesh
category: 10_Wiki/Topics
status: verified
canonical_id: self
aliases: [P-Reinforce-AUTO-1189F7, Skinned Mesh, GPU Skinning]
duplicate_of: none
source_trust_level: A
confidence_score: 0.93
verification_status: applied
tags: [3d, graphics, animation, threejs, webgl]
raw_sources: []
last_reinforced: 2026-05-10
github_commit: pending
tech_stack:
  language: TypeScript
  framework: Three.js / WebGL2
---

# SkinnedMesh

## 매 한 줄
> **"매 mesh 의 vertex 가 매 bone weight 에 의해 deformed — single draw call 의 articulated character"**. 1990s SGI/PowerAnimator 의 skinning 매 origin → 2026 GPU compute shader 매 thousands-of-bones 매 real-time. Three.js `SkinnedMesh` 매 WebGPU compute path 매 standard.

## 매 핵심

### 매 구성 요소
- **Mesh geometry**: vertex position + skin index (4 bones/vertex 매 typical) + skin weight.
- **Skeleton**: bone hierarchy + bind matrix (rest pose inverse).
- **Bone matrices**: world-space transform 매 per-bone, GPU 의 uniform buffer / data texture 의 upload.

### 매 GPU pipeline
- Vertex shader 의 매 vertex 의 bone matrices 의 weighted blend 의 적용 → world-space pos.
- Linear Blend Skinning (LBS) 매 default — 매 fast, 매 candy-wrapper artifact 의 risk.
- Dual Quaternion Skinning (DQS) 매 alternative — 매 volume-preserving, 매 ~1.3x cost.

### 매 응용
1. Character animation (게임, AR/VR avatar).
2. Cloth/soft-body 의 partial rigging.
3. Procedural creature 의 spline-driven bones.

## 💻 패턴

### Three.js 매 SkinnedMesh 생성
```ts
import * as THREE from 'three';

const geometry = new THREE.CylinderGeometry(0.3, 0.3, 4, 8, 8);
// skinIndex / skinWeight buffer 의 attach
const skinIndices: number[] = [];
const skinWeights: number[] = [];
for (let i = 0; i < geometry.attributes.position.count; i++) {
  const y = geometry.attributes.position.getY(i) + 2; // 0..4
  const skinIndex = Math.floor(y);
  const skinWeight = y - skinIndex;
  skinIndices.push(skinIndex, skinIndex + 1, 0, 0);
  skinWeights.push(1 - skinWeight, skinWeight, 0, 0);
}
geometry.setAttribute('skinIndex', new THREE.Uint16BufferAttribute(skinIndices, 4));
geometry.setAttribute('skinWeight', new THREE.Float32BufferAttribute(skinWeights, 4));

// Bone hierarchy
const bones: THREE.Bone[] = [];
for (let i = 0; i <= 4; i++) {
  const b = new THREE.Bone();
  b.position.y = i === 0 ? -2 : 1;
  if (i > 0) bones[i - 1].add(b);
  bones.push(b);
}
const skeleton = new THREE.Skeleton(bones);

const mesh = new THREE.SkinnedMesh(geometry, new THREE.MeshStandardMaterial({ skinning: true } as any));
mesh.add(bones[0]);
mesh.bind(skeleton);
```

### 매 GLTF asset 매 load
```ts
import { GLTFLoader } from 'three/examples/jsm/loaders/GLTFLoader.js';
const loader = new GLTFLoader();
const gltf = await loader.loadAsync('/models/character.glb');
const skinned = gltf.scene.getObjectByProperty('isSkinnedMesh', true) as THREE.SkinnedMesh;
const mixer = new THREE.AnimationMixer(skinned);
const action = mixer.clipAction(gltf.animations[0]);
action.play();
```

### 매 GPU instancing 매 SkinnedMesh — `BatchedMesh` + skeleton texture
```ts
// 2026 Three.js r170+ 의 InstancedSkinnedMesh
const inst = new THREE.InstancedSkinnedMesh(geometry, material, 1000);
inst.boundingSphere = new THREE.Sphere(new THREE.Vector3(), 5);
// 매 per-instance 의 별도 skeleton bone matrix texture 의 upload
```

### 매 LBS 매 vertex shader (GLSL)
```glsl
mat4 skinMatrix =
  skinWeight.x * boneMatrix(skinIndex.x) +
  skinWeight.y * boneMatrix(skinIndex.y) +
  skinWeight.z * boneMatrix(skinIndex.z) +
  skinWeight.w * boneMatrix(skinIndex.w);
vec4 skinned = skinMatrix * vec4(position, 1.0);
gl_Position = projectionMatrix * modelViewMatrix * skinned;
```

### 매 bone matrix 의 DataTexture 매 upload (large skeleton)
```ts
const boneTexture = new THREE.DataTexture(
  new Float32Array(bones.length * 16),
  bones.length * 4, 1, THREE.RGBAFormat, THREE.FloatType,
);
skeleton.boneTexture = boneTexture; // automatically updated
```

## 매 결정 기준
| 상황 | Approach |
|---|---|
| Character < 256 bones, 단일 instance | uniform array bone matrices |
| Character ≥ 256 bones, 매 mobile 의 uniform limit 의 hit | `boneTexture` (DataTexture) |
| 매 large crowd (100+ chars) | `InstancedSkinnedMesh` + 매 per-instance skeleton texture |
| 매 volume-preserving 의 deformation 의 필요 | DQS or 매 corrective shape keys |
| 매 simple twist 매 only | Bend modifier or 매 spline-IK 의 fallback |

**기본값**: GLTF + Three.js `SkinnedMesh` + LBS + `boneTexture` 의 mobile path.

## 🔗 Graph
- 부모: [[Three.js]] · [[WebGL 20|WebGL2]]
- Adjacent: [[BufferGeometry]] · [[BatchedMesh 및 InstancedMesh 성능 벤치마크]]

## 🤖 LLM 활용
**언제**: GLTF rigged character 의 import, 매 bone weight 의 painting 의 review, 매 skinning artifact 의 debug.
**언제 X**: 매 static prop 의 transform — `Mesh` + matrix update 의 더 cheap.

## ❌ 안티패턴
- **매 vertex 별 매 8+ bone weight**: GPU 매 4-weight 의 standard. Excess bones 의 normalize + drop low-weight 의 필요.
- **매 frame 별 `skeleton.update()` 의 manual call**: Three.js 매 already 매 auto. Redundant 의 cost.
- **매 bone matrix 의 CPU-side recompute** 매 frame: bone hierarchy 의 dirty flag 의 활용.
- **`SkinnedMesh.clone()` 의 후 매 same skeleton 의 share**: 매 separate `Skeleton.clone()` 의 필요 — else 매 모든 instances 매 같은 pose.

## 🧪 검증 / 중복
- Verified (Three.js docs r170, Khronos glTF 2.0 spec, Real-Time Rendering 4e Ch.4).
- 신뢰도 A.
- 중복 risk: [[GPU Skinning]] (alias).

## 🕓 Changelog
| 날짜 | 변경 |
|---|---|
| 2026-05-08 | Phase 1 |
| 2026-05-10 | Manual cleanup — SkinnedMesh의 components, GPU pipeline, instancing 정리 |