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10_Wiki/Topics 대규모 정리: - 오류 캡처/미완성 stub 문서 227개 제거 - 교차폴더 중복 43클러스터 병합 (63파일 → redirect) - 링크명 정규화: 깨진 링크 수정·redirect 직결·개념 매핑 ~2,400건 - 카테고리 MOC 6개 신규 생성 - Graph 섹션 미해결 related-keyword 링크 10,058건 제거 Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
184 lines
6.5 KiB
Markdown
184 lines
6.5 KiB
Markdown
---
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id: wiki-2026-0508-cad-렌더링-최적화
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title: CAD 렌더링 최적화
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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: [CAD Rendering Optimization, CAD Performance, Engineering Visualization]
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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: [cad, rendering, gpu, lod, webgpu]
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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: TypeScript
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framework: WebGPU/Three.js
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---
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# CAD 렌더링 최적화
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## 매 한 줄
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> **"매 millions-of-triangles model 의 60fps 표시 = LOD + culling + GPU instancing 의 합."**. 매 CAD assembly 는 mechanical part 가 hundreds-of-thousands 단위로 쌓여 brute-force rendering 시 GPU 가 즉사. 매 2026 모던 stack 은 WebGPU + meshlet (Nanite-style) + indirect draw 를 사용해 browser 에서도 native-like performance 달성.
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## 매 핵심
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### 매 bottleneck axis
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- **Geometry**: 매 triangle count — 매 fillet/thread 같은 detail 이 수십 million 까지 폭증.
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- **Draw call**: 매 part 별 separate draw → CPU/GPU sync overhead 가 frame budget 잠식.
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- **Overdraw**: 매 transparent assembly 의 layered fragment shading.
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- **Memory**: 매 32-bit index + per-vertex normal/UV/color → VRAM 빠르게 saturate.
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### 매 technique stack
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- **Tessellation control**: 매 NURBS → mesh 변환 시 view-dependent chord tolerance.
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- **LOD**: 매 distance / screen-coverage 기반 mesh swap.
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- **Frustum / occlusion culling**: 매 BVH + Hi-Z buffer.
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- **Instancing**: 매 동일 part (bolt/screw) 의 single draw call.
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- **Meshlet (Nanite-like)**: 매 cluster 단위 GPU culling + virtual geometry.
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- **Deferred shading**: 매 overdraw 비용 절감.
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### 매 응용
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1. **Onshape / Fusion 360 web**: 매 browser 안 assembly editing.
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2. **Plant 3D walkthrough**: 매 oil refinery / factory digital twin.
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3. **AR overlay**: 매 Vision Pro / Quest 3 의 maintenance instruction.
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4. **VR design review**: 매 stakeholder 의 immersive walkthrough.
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## 💻 패턴
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### Screen-space LOD selection
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```typescript
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function pickLOD(part: CadPart, camera: Camera): number {
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const screenCoverage = projectedRadius(part.bounds, camera) / camera.viewport.height;
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if (screenCoverage > 0.3) return 0; // full mesh
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if (screenCoverage > 0.1) return 1; // 1/4 triangles
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if (screenCoverage > 0.03) return 2; // 1/16 triangles
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if (screenCoverage > 0.005) return 3; // billboard
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return -1; // cull entirely
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}
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```
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### GPU instancing for fasteners
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```typescript
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const boltMesh = loadMesh('m6_socket_head.glb');
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const transforms = new Float32Array(boltCount * 16); // packed mat4
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fillTransforms(transforms, boltInstances);
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device.queue.writeBuffer(instanceBuffer, 0, transforms);
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pass.setPipeline(instancedPipeline);
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pass.setVertexBuffer(0, boltMesh.vertices);
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pass.setVertexBuffer(1, instanceBuffer);
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pass.drawIndexed(boltMesh.indexCount, boltCount); // single call for 50k bolts
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```
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### BVH-based frustum culling
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```typescript
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class BVHNode {
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bounds: AABB;
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children?: [BVHNode, BVHNode];
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parts?: CadPart[];
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}
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function cullVisible(node: BVHNode, frustum: Frustum, out: CadPart[]) {
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const test = frustum.testAABB(node.bounds);
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if (test === 'outside') return;
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if (test === 'inside' || !node.children) {
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out.push(...(node.parts ?? collectAll(node)));
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return;
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}
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cullVisible(node.children[0], frustum, out);
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cullVisible(node.children[1], frustum, out);
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}
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```
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### Meshlet cluster (Nanite-style)
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```wgsl
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// WebGPU compute shader — cluster culling
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@group(0) @binding(0) var<storage, read> meshlets: array<Meshlet>;
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@group(0) @binding(1) var<storage, read_write> visibleList: array<u32>;
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@group(0) @binding(2) var<uniform> camera: Camera;
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@compute @workgroup_size(64)
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fn cullMeshlets(@builtin(global_invocation_id) gid: vec3u) {
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let idx = gid.x;
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if (idx >= arrayLength(&meshlets)) { return; }
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let m = meshlets[idx];
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if (frustumTest(m.boundingSphere, camera) &&
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coneTest(m.normalCone, camera.position)) {
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let slot = atomicAdd(&visibleList[0], 1u);
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visibleList[slot + 1u] = idx;
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}
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}
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```
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### Indirect draw aggregation
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```typescript
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// One draw call dispatches all visible meshlets
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const drawArgs = new Uint32Array([
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indexCount, instanceCount, firstIndex, baseVertex, firstInstance
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]);
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device.queue.writeBuffer(indirectBuffer, 0, drawArgs);
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pass.drawIndexedIndirect(indirectBuffer, 0);
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```
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### Progressive streaming
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```typescript
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async function streamAssembly(modelId: string) {
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const manifest = await fetch(`/cad/${modelId}/manifest.json`).then(r => r.json());
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// load coarse first → user sees something instantly
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for (const lod of [3, 2, 1, 0]) {
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await Promise.all(manifest.parts.map(p =>
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cache.has(`${p.id}_lod${lod}`) ? null : loadPart(p, lod)
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));
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requestRedraw();
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}
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}
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```
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### Hi-Z occlusion
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```typescript
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// Down-sampled depth pyramid → occluder test before draw
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const hiZ = buildHiZPyramid(depthTexture);
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for (const part of visibleAfterFrustum) {
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if (occludedByHiZ(part.bounds, hiZ, camera)) continue;
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drawList.push(part);
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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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| < 100k triangles, single part | brute force, no LOD |
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| 1M-10M triangles, assembly | BVH + frustum culling + LOD |
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| 10M-100M triangles | + GPU instancing + meshlets |
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| > 100M (plant/ship) | virtual geometry + streaming + occlusion |
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| Mobile / VR | aggressive LOD + foveated rendering |
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**기본값**: BVH culling + 4-tier LOD + instanced fasteners (covers 90% mid-size assemblies).
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## 🔗 Graph
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- 부모: [[Computer_Graphics]] · [[GPU_Architecture]]
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- 응용: [[Digital_Twin]]
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- Adjacent: [[WebGPU]] · [[Three.js]] · [[Level_of_Detail]]
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## 🤖 LLM 활용
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**언제**: CAD/BIM viewer 설계, performance bottleneck 분석, LOD threshold tuning.
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**언제 X**: photorealistic offline rendering (path tracing 영역).
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## ❌ 안티패턴
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- **Per-part separate draw call**: 매 50k draws/frame 은 어떤 GPU 도 죽음.
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- **CPU-side culling only**: 매 GPU-driven culling 없이는 modern bandwidth 활용 불가.
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- **Uniform LOD across assembly**: 매 close-up bolt 는 detail 필요, far wall 은 billboard 충분.
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- **No tessellation budget**: 매 NURBS → mesh 변환 시 chord tolerance 가 화면 무관하면 메모리 폭발.
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## 🧪 검증 / 중복
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- Verified (Onshape engineering blog 2025, Unreal Nanite SIGGRAPH 2021, WebGPU spec 2024).
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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 — CAD rendering pipeline, LOD, meshlet, WebGPU patterns |
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