> ## Documentation Index
> Fetch the complete documentation index at: https://docs.facebetter.net/llms.txt
> Use this file to discover all available pages before exploring further.

# Quick Start

> Build and run the Facebetter C++ desktop demo on Linux (GLFW + ImGui)

This guide explains how to build and run the Facebetter C++ desktop demo on Linux. The demo is built with **GLFW + Dear ImGui + OpenGL 3**: the left panel shows a live beauty-processed preview, while the right panel provides sliders to control each effect in real time.

## Requirements

| Tool                        | Version                                                                    |
| --------------------------- | -------------------------------------------------------------------------- |
| GCC or Clang                | C++17 support required (GCC 7+ / Clang 5+)                                 |
| CMake                       | 3.16+                                                                      |
| Ninja                       | Any recent version (`apt install ninja-build` / `dnf install ninja-build`) |
| OpenGL dev libraries        | `libgl1-mesa-dev` (Ubuntu/Debian) or `mesa-libGL-devel` (Fedora/RHEL)      |
| X11 / Wayland dev libraries | Required by GLFW (see install commands below)                              |

### Install Dependencies (Ubuntu / Debian)

```bash theme={null}
sudo apt update
sudo apt install -y build-essential cmake ninja-build \
    libgl1-mesa-dev libglu1-mesa-dev \
    libx11-dev libxrandr-dev libxinerama-dev \
    libxcursor-dev libxi-dev
```

### Install Dependencies (Fedora / RHEL)

```bash theme={null}
sudo dnf install -y gcc-c++ cmake ninja-build \
    mesa-libGL-devel mesa-libGLU-devel \
    libX11-devel libXrandr-devel libXinerama-devel \
    libXcursor-devel libXi-devel
```

## Step 1: Clone the Repository

```bash theme={null}
git clone https://github.com/pixpark/facebetter-sdk.git
cd facebetter-sdk
```

## Step 2: Place the SDK Files

Place the Linux SDK files under `demo/cpp/sdk/`:

```
demo/cpp/sdk/
├── include/
│   └── facebetter/
│       ├── beauty_effect_engine.h
│       ├── beauty_params.h
│       ├── image_frame.h
│       └── type_defines.h
├── lib/
│   └── libfacebetter.so    ← shared library
└── resource/
    └── resource.fbd        ← model and resource pack
```

<Tip>
  The SDK download link is available on the [Download](https://facebetter.net/download) page or in your dashboard.
</Tip>

## Step 3: Build

```bash theme={null}
cd demo/cpp
cmake -B build -G "Ninja" -DCMAKE_BUILD_TYPE=Release
cmake --build build
```

After the build, CMake automatically copies `resource/resource.fbd` and `demo.png` (if present) to `build/resource/`.

## Step 4: Prepare a Preview Image (optional)

Place any face photo named `demo.png` in `demo/cpp/`:

```
demo/cpp/demo.png
```

The engine will process the image at \~30 fps and display the result in the left panel.

## Step 5: Run

```bash theme={null}
cd demo/cpp/build

# Option A: add the library path at runtime
LD_LIBRARY_PATH=../sdk/lib ./facebetter_demo

# Option B: copy the shared library next to the executable
cp ../sdk/lib/libfacebetter.so .
./facebetter_demo
```

Once running, the window shows:

* **Left panel** – live beauty-processed preview
* **Right panel** – Beauty Control Panel:
  * **Basic Beauty**: Smoothing / Whitening / Rosiness / Sharpening
  * **Face Reshape**: Face Thin / V Face / Narrow Face / Short Face / Cheekbone / Jawbone / Chin / Nose Slim / Eye Size / Eye Distance
  * **Makeup**: Lipstick / Blush
  * **Sticker**: dropdown (Off / rabbit)

Click **Reset All** to restore all parameters to zero.

## Troubleshooting

**Q: `libfacebetter.so: cannot open shared object file`**\
A: Run with `LD_LIBRARY_PATH=../sdk/lib ./facebetter_demo`, copy the library to the executable directory, or add the path to `/etc/ld.so.conf` and run `ldconfig`.

**Q: CMake cannot find OpenGL**\
A: Install `libgl1-mesa-dev` (Ubuntu) or `mesa-libGL-devel` (Fedora), then re-run CMake.

**Q: Window shows "Put demo.png …"**\
A: Place a face photo named `demo.png` in `demo/cpp/` and restart the demo.

**Q: `GLFW: X11: Display variable not set`**\
A: Make sure you are running in a graphical session, or set the `DISPLAY` environment variable.