docs(10_Wiki): Topic_Business/General/Graphic/Programming을 Topics/ 하위로 이동
최상위 10_Wiki/Topic_*였던 4개 카테고리 폴더를 10_Wiki/Topics/Topic_* 로 재배치. 콘텐츠 변경 없음(순수 폴더 이동) — Topics/ 하위 나머지 폴더는 이미 지난 커밋에서 전부 정리된 상태(잔존 항목은 에이전트 운영 상태 및 사용자가 보존을 요청한 업데이트0615/무제 3.canvas 뿐).
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Antigravity Agent
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id: wiki-2026-0508-instancing
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title: Instancing
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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: [GPU instancing, instanced rendering, drawInstanced]
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duplicate_of: none
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source_trust_level: A
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confidence_score: 0.95
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verification_status: applied
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tags: [graphics, gpu, webgl, webgpu, threejs, 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: GLSL/WGSL
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framework: Three.js/WebGPU
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---
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# Instancing
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## 매 한 줄
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> **"매 동일 mesh 를 N 번 그릴 때 single draw call 로 묶는 GPU 기법 — 매 per-instance attribute (transform, color) 만 다르게"**. 매 thousands → millions of objects 가 60fps 로 가능. 매 grass, particles, crowd, foliage 의 핵심. WebGL 2 / WebGPU / Vulkan / Metal 모두 native 지원.
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## 매 핵심
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### 매 왜 빠른가
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- **Draw call overhead 제거**: 매 CPU→GPU command 1번 만.
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- **Vertex buffer reuse**: 매 base mesh 1개, instance attr 만 streaming.
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- **GPU parallelism**: 매 instance 가 각 SM/CU 에 분산.
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### 매 per-instance attribute 종류
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- **Transform matrix** (mat4) — 매 가장 흔함.
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- **Color / tint** (vec4)
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- **Texture index** / atlas UV offset
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- **Animation frame** (skinned crowd)
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### 매 응용
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1. Three.js `InstancedMesh` — 매 50k tree, 100k particle.
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2. Unreal HISM / Niagara, Unity GPU Instancer.
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3. WebGPU compute-driven instancing — 매 frustum culling on GPU.
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4. Game KvK map — 매 thousands of city/troop sprite.
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## 💻 패턴
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### Three.js InstancedMesh
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```javascript
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import * as THREE from "three";
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const geometry = new THREE.BoxGeometry(1, 1, 1);
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const material = new THREE.MeshStandardMaterial({ color: 0x44aa88 });
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const count = 10000;
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const mesh = new THREE.InstancedMesh(geometry, material, count);
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const m = new THREE.Matrix4();
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for (let i = 0; i < count; i++) {
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m.setPosition(
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(Math.random() - 0.5) * 100,
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0,
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(Math.random() - 0.5) * 100,
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);
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mesh.setMatrixAt(i, m);
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}
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mesh.instanceMatrix.needsUpdate = true;
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scene.add(mesh);
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```
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### Per-instance color
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```javascript
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const colors = new Float32Array(count * 3);
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for (let i = 0; i < count; i++) {
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colors[i * 3] = Math.random();
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colors[i * 3 + 1] = Math.random();
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colors[i * 3 + 2] = Math.random();
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}
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geometry.setAttribute(
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"instanceColor",
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new THREE.InstancedBufferAttribute(colors, 3),
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);
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material.onBeforeCompile = (shader) => {
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shader.vertexShader = shader.vertexShader
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.replace("#include <common>", "#include <common>\nattribute vec3 instanceColor; varying vec3 vColor;")
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.replace("#include <begin_vertex>", "#include <begin_vertex>\nvColor = instanceColor;");
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shader.fragmentShader = shader.fragmentShader
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.replace("#include <common>", "#include <common>\nvarying vec3 vColor;")
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.replace("vec4 diffuseColor = vec4( diffuse, opacity );", "vec4 diffuseColor = vec4( diffuse * vColor, opacity );");
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};
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```
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### Update single instance (game troop move)
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```javascript
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function updateTroop(idx: number, x: number, z: number) {
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m.setPosition(x, 0, z);
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mesh.setMatrixAt(idx, m);
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mesh.instanceMatrix.needsUpdate = true; // 매 dirty flag
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}
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// 매 N 변경 시 partial range update (Three r150+)
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mesh.instanceMatrix.addUpdateRange(start * 16, count * 16);
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```
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### WebGPU instanced draw
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```javascript
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// WGSL vertex shader
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const wgsl = `
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struct Instance { @location(3) m0: vec4f, @location(4) m1: vec4f, @location(5) m2: vec4f, @location(6) m3: vec4f };
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@vertex fn vs(@location(0) pos: vec3f, instance: Instance) -> @builtin(position) vec4f {
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let model = mat4x4f(instance.m0, instance.m1, instance.m2, instance.m3);
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return uniforms.viewProj * model * vec4f(pos, 1.0);
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}`;
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// JS — drawIndexedIndirect 또는 draw with instanceCount
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pass.draw(vertexCount, instanceCount, 0, 0);
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```
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### GPU frustum culling (compute → instanced draw)
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```wgsl
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@compute @workgroup_size(64)
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fn cull(@builtin(global_invocation_id) gid: vec3u) {
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let idx = gid.x;
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if (idx >= arrayLength(&instances)) { return; }
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let m = instances[idx];
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if (inFrustum(m.bbox)) {
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let out = atomicAdd(&visibleCount, 1u);
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visibleInstances[out] = m;
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}
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}
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// 매 visibleInstances + visibleCount → drawIndirect
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```
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### Foliage with wind (vertex shader animation)
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```glsl
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attribute mat4 instanceMatrix;
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uniform float uTime;
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void main() {
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vec3 p = position;
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float wind = sin(uTime + instanceMatrix[3].x * 0.1) * 0.1 * p.y;
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p.x += wind;
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gl_Position = projectionMatrix * viewMatrix * instanceMatrix * vec4(p, 1.0);
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}
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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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| Same mesh, ≥100 copies | InstancedMesh |
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| Different meshes, similar | BatchedMesh (Three r155+) |
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| Dynamic count + culling | GPU compute culling + drawIndirect |
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| Skinned crowd | Texture-baked anim + instancing |
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| Just 10 copies | 매 그냥 N draw — 매 instancing overhead 작음 |
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**기본값**: ≥100 copies of same mesh → InstancedMesh.
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## 🔗 Graph
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- 부모: [[Draw Call Optimization]]
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- 변형: [[BatchedMesh]] · [[Indirect Drawing]]
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- 응용: [[Three.js]] · [[WebGPU]]
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- Adjacent: [[Frustum Culling]] · [[LOD]]
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## 🤖 LLM 활용
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**언제**: large-scale rendering 설계, particle / foliage / crowd 구현.
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**언제 X**: 매 single object, 매 매우 다른 mesh — 매 instancing overhead 정당화 X.
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## ❌ 안티패턴
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- **needsUpdate = true on every frame**: 매 모든 instance 변경 안 했어도 전체 upload — 매 partial update range 사용.
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- **instancing for unique meshes**: 매 효과 X — 매 BatchedMesh 또는 multi-draw indirect.
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- **CPU-side culling per instance**: 매 GPU compute 가 더 빠름 (10k+).
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## 🧪 검증 / 중복
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- Verified (Three.js docs, WebGPU spec, Real-Time Rendering 4th ed.).
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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 — Three.js + WebGPU instancing 패턴 |
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