2nd/10_Wiki/Topics/Domain_Programming/Architecture/Real-Time Engine (RTE).md

---
id: wiki-2026-0508-real-time-engine-rte
title: Real-Time Engine (RTE)
category: 10_Wiki/Topics
status: verified
canonical_id: self
aliases: [RTE, Real-Time Game Engine, Real-Time Rendering Engine]
duplicate_of: none
source_trust_level: A
confidence_score: 0.9
verification_status: applied
tags: [gamedev, rendering, engine, real-time]
raw_sources: []
last_reinforced: 2026-05-10
github_commit: pending
tech_stack:
  language: cpp
  framework: unreal-unity-bevy
---

# Real-Time Engine (RTE)

## 매 한 줄
> **"매 16ms (60fps) / 8ms (120fps) budget 매 frame 매 모든 sim+render"**. Unreal 5.5 / Unity 6 / Godot 4 / Bevy / O3DE — 매 2026 stack. 매 Nanite + Lumen + ML upscaling (DLSS 4, FSR 4) 매 default.

## 매 핵심

### 매 frame anatomy
- **Input** (~1ms): controller, mouse, network input.
- **Game tick** (1-3ms): AI, physics, gameplay scripts.
- **Animation** (1-2ms): skeletal blend, IK.
- **Render prep** (1-2ms): culling, batching.
- **GPU render** (5-10ms): shadows, GBuffer, lighting, post.
- **Present**: vsync / VRR.

### 매 subsystems
- **Renderer**: forward / deferred / clustered; raytracing + rasterization hybrid.
- **Physics**: PhysX, Jolt, Havok, Bullet — rigid + soft + cloth.
- **Audio**: Wwise, FMOD, MetaSound — spatial, ducking.
- **Networking**: replication, prediction, rollback netcode (GGPO).
- **Animation**: state machines, ML motion (Learned Motion Matching).
- **Streaming**: World Partition (UE5), addressables (Unity).

### 매 응용
1. AAA games (Fortnite UE5, Genshin Impact custom).
2. Cinematic / virtual production (LED wall, ICVFX).
3. Digital twins / sim (NVIDIA Omniverse).
4. ArchViz real-time (Twinmotion, Enscape).
5. Robotics sim (Isaac Sim, Unity ML-Agents).

## 💻 패턴

### Game loop (fixed + variable)
```cpp
double accumulator = 0.0;
constexpr double dt = 1.0 / 60.0;
while (running) {
    double frameTime = std::min(clock.tick(), 0.25);
    accumulator += frameTime;
    while (accumulator >= dt) {
        physics.step(dt);    // fixed
        accumulator -= dt;
    }
    double alpha = accumulator / dt;
    render(state.interpolate(alpha));  // variable
}
```

### ECS — Bevy (Rust)
```rust
use bevy::prelude::*;

#[derive(Component)] struct Velocity(Vec3);
#[derive(Component)] struct Position(Vec3);

fn movement(mut q: Query<(&mut Position, &Velocity)>, time: Res<Time>) {
    for (mut p, v) in &mut q {
        p.0 += v.0 * time.delta_seconds();
    }
}

fn main() {
    App::new()
        .add_plugins(DefaultPlugins)
        .add_systems(Update, movement)
        .run();
}
```

### Unity DOTS (Burst-compiled job)
```csharp
[BurstCompile]
partial struct MoveJob : IJobEntity {
    public float DeltaTime;
    void Execute(ref LocalTransform t, in Velocity v) {
        t.Position += v.Value * DeltaTime;
    }
}
```

### Unreal Engine (C++ actor tick)
```cpp
void AEnemy::Tick(float dt) {
    Super::Tick(dt);
    FVector toPlayer = Player->GetActorLocation() - GetActorLocation();
    AddMovementInput(toPlayer.GetSafeNormal(), 1.0f);
}
```

### Render — compute shader (HLSL)
```hlsl
[numthreads(16, 16, 1)]
void CSMain(uint3 id : SV_DispatchThreadID) {
    float3 normal = NormalTex[id.xy].xyz * 2.0 - 1.0;
    float3 lightDir = normalize(LightPos - WorldPos[id.xy].xyz);
    float ndl = saturate(dot(normal, lightDir));
    Output[id.xy] = float4(Albedo[id.xy].rgb * ndl, 1);
}
```

### Rollback netcode (GGPO-style)
```cpp
// Save state every frame, rollback on input arrival
void onInputReceived(int frame, Input input) {
    if (frame < currentFrame) {
        loadState(frame);
        for (int f = frame; f <= currentFrame; f++) {
            simulate(f, getInputs(f));
        }
    }
}
```

### ML upscaling integration (DLSS 4 / FSR 4 — 2026)
```cpp
// Render at 1080p internal, upscale to 4K, frame-gen to 240fps
DLSSContext ctx;
ctx.initialize(width=1920, height=1080, target_w=3840, target_h=2160);
ctx.evaluate(colorIn, motionVectors, depth, jitter, colorOut);
```

## 매 결정 기준
| 상황 | Engine |
|---|---|
| 매 AAA, photoreal | Unreal 5.5 + Nanite/Lumen |
| 매 cross-platform indie | Unity 6 / Godot 4 |
| 매 Rust-native, ECS | Bevy |
| 매 mobile-first | Unity / Godot |
| 매 simulation / robotics | Isaac Sim / Omniverse |
| 매 fighting game | Custom + GGPO rollback |
| 매 multiplayer FPS | Unreal + Iris/Replication |

**기본값**: 매 unknown scope → Unreal 5.5 (free, AAA features). 매 indie → Godot 4.

## 🔗 Graph
- 부모: [[Real-time Rendering]]
- 변형: [[Unity]] · [[Bevy]]
- 응용: [[Digital Twin]]
- Adjacent: [[ECS]] · [[Nanite]] · [[Rollback Netcode]]

## 🤖 LLM 활용
**언제**: 매 shader scaffolding, 매 gameplay script generation (Blueprint → C++), 매 procedural content prompts. 매 Unreal Copilot / Unity Muse.
**언제 X**: 매 hot-path optimization — LLM 매 microarchitecture 매 weak. 매 profiler-driven manual.

## ❌ 안티패턴
- **GC in hot path**: 매 frame spike — pool / arena allocator.
- **Unbatched draw calls**: 매 1000+ per frame — instancing / Nanite.
- **Sync I/O on game thread**: 매 hitch. 매 async streaming.
- **Variable physics dt**: 매 nondeterministic — fixed timestep + interpolate.
- **No frame budgeting**: 매 unconstrained subsystem — profile + cap.

## 🧪 검증 / 중복
- Verified (Game Engine Architecture — Gregory 3rd ed; Unreal/Unity docs).
- 신뢰도 A.

## 🕓 Changelog
| 날짜 | 변경 |
|---|---|
| 2026-05-08 | Phase 1 |
| 2026-05-10 | Manual cleanup — full RTE entry with 2026 engines |