2nd/10_Wiki/Topics/AI_and_ML/렌더링 파이프라인(Rendering Pipeline).md

---
id: wiki-2026-0508-렌더링-파이프라인-rendering-pipeline
title: 렌더링 파이프라인(Rendering Pipeline)
category: 10_Wiki/Topics
status: verified
canonical_id: self
aliases: [Rendering Pipeline, Graphics Pipeline, GPU Pipeline]
duplicate_of: none
source_trust_level: A
confidence_score: 0.9
verification_status: applied
tags: [graphics, gpu, rendering, real-time]
raw_sources: []
last_reinforced: 2026-05-10
github_commit: pending
tech_stack:
  language: glsl/wgsl
  framework: Vulkan / DirectX 12 / WebGPU
---

# 렌더링 파이프라인(Rendering Pipeline)

## 매 한 줄
> **"매 vertex → fragment → screen pixel로 변환하는 GPU의 stage chain"**. 1990s fixed-function OpenGL에서 시작 → programmable shaders (GeForce 3, 2001) → modern compute-driven pipeline (mesh shaders, DX12 Ultimate)으로 evolve. 2026 현재 Vulkan 1.4 · DirectX 12 Ultimate · WebGPU가 cross-platform standard, ray-traced GI + neural rendering (DLSS 4, FSR 4)이 default.

## 매 핵심

### 매 Classic Pipeline (Stages)
- **Input Assembly (IA)**: 매 vertex buffer + index buffer → primitive.
- **Vertex Shader (VS)**: 매 per-vertex transform (world → view → clip).
- **Tessellation / Geometry**: 매 optional — adaptive subdivision, particle expansion.
- **Rasterization**: 매 primitive → fragments (interpolated).
- **Fragment / Pixel Shader (FS)**: 매 per-pixel shading (PBR, lighting).
- **Output Merger**: 매 depth/stencil test + blend → framebuffer.

### 매 Modern Compute-Driven
- **Mesh Shaders** (DX12 Ultimate, Vulkan): 매 IA + VS + Geom 대체, GPU-driven culling.
- **Ray Tracing**: 매 RT cores → BVH traversal → shadow / GI / reflection.
- **Variable Rate Shading (VRS)**: 매 영역별 shading rate 조절.
- **Neural Upscaling**: 매 DLSS 4 / FSR 4 / XeSS 2 — render at 1/4 res, upsample to 4K.

### 매 응용
1. Unreal Engine 5 Nanite — virtualized geometry, mesh-shader based.
2. Unity HDRP — render graph, customizable per-frame.
3. WebGPU (Chrome 120+) — browser-native compute + render.
4. Godot 4.4 — Vulkan-first, mobile-aware forward+ renderer.

## 💻 패턴

### WebGPU Render Pipeline Setup
```javascript
const pipeline = device.createRenderPipeline({
  layout: 'auto',
  vertex: {
    module: device.createShaderModule({ code: vsWGSL }),
    entryPoint: 'main',
    buffers: [{
      arrayStride: 32,
      attributes: [
        { shaderLocation: 0, offset: 0, format: 'float32x3' },  // pos
        { shaderLocation: 1, offset: 12, format: 'float32x3' }, // normal
        { shaderLocation: 2, offset: 24, format: 'float32x2' }, // uv
      ],
    }],
  },
  fragment: {
    module: device.createShaderModule({ code: fsWGSL }),
    entryPoint: 'main',
    targets: [{ format: 'bgra8unorm' }],
  },
  primitive: { topology: 'triangle-list', cullMode: 'back' },
  depthStencil: { format: 'depth24plus', depthWriteEnabled: true, depthCompare: 'less' },
});
```

### Forward+ Tiled Light Culling (WGSL compute)
```wgsl
@group(0) @binding(0) var<storage, read> lights: array<Light>;
@group(0) @binding(1) var<storage, read_write> tile_lights: array<u32>;
@group(0) @binding(2) var depth_tex: texture_depth_2d;

@compute @workgroup_size(16, 16)
fn cs_main(@builtin(global_invocation_id) gid: vec3<u32>) {
  let tile = gid.xy / 16u;
  let frustum = build_tile_frustum(tile, depth_tex);
  var idx: u32 = 0u;
  for (var i = 0u; i < arrayLength(&lights); i = i + 1u) {
    if (sphere_in_frustum(lights[i].pos_radius, frustum)) {
      tile_lights[tile_offset(tile) + idx] = i;
      idx = idx + 1u;
    }
  }
}
```

### Vulkan Command Buffer
```cpp
VkCommandBufferBeginInfo begin{VK_STRUCTURE_TYPE_COMMAND_BUFFER_BEGIN_INFO};
vkBeginCommandBuffer(cmd, &begin);

VkRenderingAttachmentInfo color{};
color.sType = VK_STRUCTURE_TYPE_RENDERING_ATTACHMENT_INFO;
color.imageView = swapchainView;
color.imageLayout = VK_IMAGE_LAYOUT_COLOR_ATTACHMENT_OPTIMAL;
color.loadOp = VK_ATTACHMENT_LOAD_OP_CLEAR;
color.storeOp = VK_ATTACHMENT_STORE_OP_STORE;
color.clearValue = {.color = {{0, 0, 0, 1}}};

VkRenderingInfo info{VK_STRUCTURE_TYPE_RENDERING_INFO};
info.renderArea = {{0, 0}, extent};
info.layerCount = 1;
info.colorAttachmentCount = 1;
info.pColorAttachments = &color;

vkCmdBeginRendering(cmd, &info);
vkCmdBindPipeline(cmd, VK_PIPELINE_BIND_POINT_GRAPHICS, pipeline);
vkCmdDraw(cmd, 3, 1, 0, 0);
vkCmdEndRendering(cmd);
vkEndCommandBuffer(cmd);
```

### PBR Fragment Shader (WGSL)
```wgsl
fn fresnel_schlick(cos_theta: f32, F0: vec3<f32>) -> vec3<f32> {
  return F0 + (vec3(1.0) - F0) * pow(1.0 - cos_theta, 5.0);
}

fn distribution_ggx(N: vec3<f32>, H: vec3<f32>, roughness: f32) -> f32 {
  let a = roughness * roughness;
  let a2 = a * a;
  let NdotH = max(dot(N, H), 0.0);
  let denom = (NdotH * NdotH * (a2 - 1.0) + 1.0);
  return a2 / (3.14159 * denom * denom);
}

@fragment
fn fs_main(in: VsOut) -> @location(0) vec4<f32> {
  let N = normalize(in.normal);
  let V = normalize(camera_pos - in.world_pos);
  let L = normalize(light_pos - in.world_pos);
  let H = normalize(V + L);

  let F0 = mix(vec3(0.04), albedo, metallic);
  let F = fresnel_schlick(max(dot(H, V), 0.0), F0);
  let D = distribution_ggx(N, H, roughness);
  let G = geometry_smith(N, V, L, roughness);

  let specular = (D * G * F) / (4.0 * max(dot(N, V), 0.001) * max(dot(N, L), 0.001));
  let kD = (vec3(1.0) - F) * (1.0 - metallic);
  let diffuse = kD * albedo / 3.14159;
  let radiance = light_color * max(dot(N, L), 0.0);
  return vec4((diffuse + specular) * radiance, 1.0);
}
```

### Render Graph (UE5-style)
```cpp
auto& depth = graph.create_texture("Depth", {1920, 1080, VK_FORMAT_D32_SFLOAT});
auto& gbuffer = graph.create_texture("GBuffer", {1920, 1080, VK_FORMAT_R16G16B16A16_SFLOAT});

graph.add_pass("GBuffer", [&](PassBuilder& b) {
    b.write(gbuffer); b.write(depth);
    return [=](CommandBuffer& cmd) { draw_opaque(cmd); };
});

graph.add_pass("Lighting", [&](PassBuilder& b) {
    b.read(gbuffer); b.read(depth); b.write(swapchain);
    return [=](CommandBuffer& cmd) { fullscreen_pass(cmd, lighting_pso); };
});

graph.compile_and_execute(cmd);
```

## 매 결정 기준
| 상황 | Approach |
|---|---|
| Cross-platform (incl. web) | WebGPU |
| AAA PC / console | Vulkan / DX12 with mesh shaders |
| Mobile-first | OpenGL ES 3.2 / Vulkan Mobile |
| Real-time RT | DXR 1.1 / Vulkan KHR_ray_tracing |
| Indie / prototype | Unity URP / Godot Forward+ |

**기본값**: Vulkan 1.3+ render-graph + forward+ tile-based + DLSS/FSR upscale.

## 🔗 Graph
- 부모: [[Computer_Graphics]] · [[GPU_Architecture]]
- 변형: [[Deferred_Rendering]]
- 응용: [[WebGPU]]

## 🤖 LLM 활용
**언제**: shader template generation, render-graph pass scaffolding, debug-message interpretation.
**언제 X**: 매 perf-critical inner loop optimization — RenderDoc / NSight profiler가 ground truth.

## ❌ 안티패턴
- **Immediate-mode draw calls**: 매 draw call 수천 → CPU bottleneck (use indirect draws).
- **Stalls on map/unmap**: 매 GPU upload 동기화 → frame hitch (use staging + double buffer).
- **No depth pre-pass**: 매 expensive overdraw on dense scenes.
- **Heavy fragment for far objects**: 매 mip / LOD 무시.

## 🧪 검증 / 중복
- Verified (Vulkan 1.4 spec, "Real-Time Rendering 4th ed", DigitalFoundry 2025 analyses).
- 신뢰도 A.

## 🕓 Changelog
| 날짜 | 변경 |
|---|---|
| 2026-05-08 | Phase 1 |
| 2026-05-10 | Manual cleanup — graphics pipeline stages + modern compute-driven + WebGPU/Vulkan code 정리 |