---
id: game-shader-patterns
title: Shader 패턴 — Vertex / Fragment / WGSL
category: Coding
status: draft
source_trust_level: B
verification_status: conceptual
created_at: 2026-05-09
updated_at: 2026-05-09
tags: [game, shader, glsl, wgsl, vibe-coding]
tech_stack: { language: "GLSL / WGSL", applicable_to: ["Game", "Frontend"] }
applied_in: []
aliases: [shader, GLSL, WGSL, vertex shader, fragment shader, post-processing]
---

# Shader Patterns

> GPU 의 작은 program. **Vertex (위치 변형) + Fragment (색)**. WebGPU = WGSL, OpenGL/WebGL = GLSL. Effect / 사후 처리 강력.

## 📖 핵심 개념
- Vertex shader: 각 vertex 변형.
- Fragment (pixel) shader: 각 pixel 색 결정.
- Uniform: CPU → GPU 변수.
- Attribute: vertex 별 data.

## 💻 코드 패턴

### 단순 fragment (GLSL)
```glsl
// fragment.glsl
precision mediump float;
varying vec2 vUv;
uniform float uTime;

void main() {
  vec3 color = vec3(
    sin(uTime + vUv.x * 6.28) * 0.5 + 0.5,
    sin(uTime + vUv.y * 6.28 + 2.09) * 0.5 + 0.5,
    sin(uTime + vUv.x * 6.28 + 4.18) * 0.5 + 0.5
  );
  gl_FragColor = vec4(color, 1.0);
}
```

### Three.js + GLSL
```ts
const material = new THREE.ShaderMaterial({
  vertexShader: `
    varying vec2 vUv;
    void main() {
      vUv = uv;
      gl_Position = projectionMatrix * modelViewMatrix * vec4(position, 1.0);
    }
  `,
  fragmentShader: `
    varying vec2 vUv;
    uniform float uTime;
    void main() {
      gl_FragColor = vec4(vUv, sin(uTime) * 0.5 + 0.5, 1.0);
    }
  `,
  uniforms: { uTime: { value: 0 } },
});

// 매 frame
material.uniforms.uTime.value = clock.getElapsedTime();
```

### WGSL (WebGPU)
```wgsl
struct VertexInput {
  @location(0) position: vec3f,
  @location(1) uv: vec2f,
}

struct VertexOutput {
  @builtin(position) position: vec4f,
  @location(0) uv: vec2f,
}

struct Uniforms {
  time: f32,
}

@group(0) @binding(0) var<uniform> u: Uniforms;

@vertex
fn vs(input: VertexInput) -> VertexOutput {
  var out: VertexOutput;
  out.position = vec4f(input.position, 1.0);
  out.uv = input.uv;
  return out;
}

@fragment
fn fs(input: VertexOutput) -> @location(0) vec4f {
  let color = vec3f(
    sin(u.time + input.uv.x * 6.28) * 0.5 + 0.5,
    sin(u.time + input.uv.y * 6.28) * 0.5 + 0.5,
    1.0
  );
  return vec4f(color, 1.0);
}
```

### 자주 쓰는 함수 (GLSL/WGSL)
```glsl
// Smoothstep — 부드러운 편향
float t = smoothstep(0.4, 0.6, dist);

// Mix — 보간
vec3 c = mix(red, blue, t);

// Distance
float d = length(uv - vec2(0.5, 0.5));

// Step
float v = step(0.5, x);  // x < 0.5 ? 0 : 1

// Noise (snoise / perlin)
// 라이브러리 또는 직접 구현
```

### Pattern: 원
```glsl
void main() {
  vec2 uv = vUv - 0.5;
  float d = length(uv);
  float circle = smoothstep(0.3, 0.29, d);
  gl_FragColor = vec4(vec3(circle), 1.0);
}
```

### Pattern: gradient
```glsl
gl_FragColor = vec4(mix(vec3(1, 0, 0), vec3(0, 0, 1), vUv.y), 1.0);
```

### Pattern: noise
```glsl
// Simple hash noise
float hash(vec2 p) {
  return fract(sin(dot(p, vec2(127.1, 311.7))) * 43758.5453);
}

float noise(vec2 p) {
  vec2 i = floor(p), f = fract(p);
  vec2 u = f * f * (3.0 - 2.0 * f);
  return mix(
    mix(hash(i), hash(i + vec2(1, 0)), u.x),
    mix(hash(i + vec2(0, 1)), hash(i + vec2(1, 1)), u.x),
    u.y
  );
}

void main() {
  float n = noise(vUv * 10.0 + uTime);
  gl_FragColor = vec4(vec3(n), 1.0);
}
```

### Post-processing (Three.js)
```ts
import { EffectComposer, RenderPass, ShaderPass } from 'three/examples/jsm/Addons.js';

const composer = new EffectComposer(renderer);
composer.addPass(new RenderPass(scene, camera));

const myPass = new ShaderPass({
  uniforms: { tDiffuse: { value: null }, uTime: { value: 0 } },
  vertexShader: ...,
  fragmentShader: `
    uniform sampler2D tDiffuse;
    uniform float uTime;
    varying vec2 vUv;
    void main() {
      vec4 color = texture2D(tDiffuse, vUv);
      // pixelate
      vec2 pixelated = floor(vUv * 100.0) / 100.0;
      color = texture2D(tDiffuse, pixelated);
      gl_FragColor = color;
    }
  `,
});
composer.addPass(myPass);
```

### Vertex displacement (wave)
```glsl
// vertex
uniform float uTime;
varying vec2 vUv;

void main() {
  vUv = uv;
  vec3 pos = position;
  pos.y += sin(pos.x * 5.0 + uTime) * 0.1;
  gl_Position = projectionMatrix * modelViewMatrix * vec4(pos, 1.0);
}
```

### Texture
```glsl
uniform sampler2D uTexture;
varying vec2 vUv;

void main() {
  vec4 color = texture2D(uTexture, vUv);
  // tint
  color.rgb *= vec3(1.0, 0.5, 0.8);
  gl_FragColor = color;
}
```

### React Three Fiber + custom material
```tsx
import { extend } from '@react-three/fiber';
import { shaderMaterial } from '@react-three/drei';

const MyMaterial = shaderMaterial(
  { uTime: 0, uColor: new THREE.Color('hotpink') },
  vertexShader,
  fragmentShader
);
extend({ MyMaterial });

function Mesh() {
  const ref = useRef<any>();
  useFrame((_, dt) => { ref.current.uTime += dt; });
  
  return (
    <mesh>
      <boxGeometry />
      <myMaterial ref={ref} />
    </mesh>
  );
}
```

### Compute shader (WebGPU only)
```wgsl
@group(0) @binding(0) var<storage, read> input: array<f32>;
@group(0) @binding(1) var<storage, read_write> output: array<f32>;

@compute @workgroup_size(64)
fn main(@builtin(global_invocation_id) id: vec3u) {
  let i = id.x;
  output[i] = input[i] * 2.0;
}
```

→ Particle simulation / image processing.

### Performance
```
- Texture lookup 비싸 — minimize.
- Branch (if) 가능한 한 적게 — uniform branch 는 OK, dynamic branch 비싼.
- Precision: highp (vertex) / mediump (fragment) 보통 OK.
- mipmaps 사용 (texture).
- Dependent texture lookup 피하기.
- Discard 비싸 — alpha test 알 됨.
```

### 디버그
```
Spector.js (browser extension): WebGL/WebGPU frame capture.
Renderdoc: native graphics debugger.
GLSL Lint (vscode): syntax 검사.

Print debug:
gl_FragColor = vec4(vec3(myValue), 1.0);
// 색으로 값 시각화.
```

### Shadertoy / The Book of Shaders
- shadertoy.com — 영감.
- thebookofshaders.com — 학습.
- 공유된 shader 가 사실상 라이브러리.

### Common shader effects
```
- Glitch / chromatic aberration
- Bloom
- DOF (depth of field)
- Outline
- Toon / cel shading
- Water / wave
- Fire / smoke
- Motion blur
- Pixelation
- Gaussian blur
- Edge detection
```

## 🤔 의사결정 기준
| 작업 | 도구 |
|---|---|
| 일반 web shader | Three.js + GLSL |
| Modern + WebGPU | R3F + WGSL |
| 2D effect | PixiJS filter |
| Image processing | WebGPU compute |
| Native game | Unity/Unreal shader graph |
| Quick prototype | Shadertoy |

## ❌ 안티패턴
- **Branch heavy 모든 fragment**: 느림. lookup texture.
- **Texture 매 frame upload**: cache.
- **High precision 모든 곳**: mediump 충분.
- **uniform 매 draw 변경**: dirty flag.
- **Discard 큰 사용**: alpha test 또는 sort.
- **Compile 매 frame**: cache.
- **Shader 큰 size**: 중복 로직 — function 분리.

## 🤖 LLM 활용 힌트
- 공유 shader (Shadertoy) → 자체 변형.
- WebGPU = WGSL (modern).
- R3F + drei `shaderMaterial` 가 가장 단순.
- Spector.js 가 디버그.

## 🔗 관련 문서
- [[Frontend_Three_R3F]]
- [[Frontend_WebGPU_Patterns]]
- [[Game_Loop_ECS]]
