# Command Line Switches

Project AirSim supports the following command line switches.  Since Project AirSim environments are built as Unreal executables, there are some Unreal command line switch options that can be useful:

| Switch | Description |
| ------ | ----------- |
| <code>&#x2011;RenderOffScreen</code> | Enable headless rendering (same for both Windows and Linux) |
| <code>&#x2011;nullrhi</code> | Disable rendering completely |
| <code>&#x2011;log</code> | For Windows, this switch will launch an additional command prompt that displays the log output as stdout (default behavior in Linux) |
| <code>&#x2011;vulkan</code> | Force Vulkan rendering instead of DirectX for Windows (Vulkan is already default for Linux)
| <code>&#x2011;ResX=</code>640 <code>&#x2011;ResY=</code>480 | Set the main viewport rendering resolution (ex. 640x480) |
| <code>&#x2011;windowed</code> | Run in windowed mode |
| <code>&#x2011;fullscreen</code> | Run in full-screen mode |
| <code>&#x2011;NoVSync</code> | Disable VSync to prevent capping FPS at the monitor's refresh rate |
| <code>&#x2011;nosound</code> | Disable any sound output |
| <code>&#x2011;benchmark</code> | Enabled Unreal's benchmark mode that seems to remove any sleeps in between rendering/tick loops to run without limiting to any real-time execution rate FPS target (this mode needs further testing to confirm any side-effects and how it could be used properly) |
| <code>&#x2011;gltfDir=</code><i>dir/containing/tiles/</i> | If you'll be using a GIS scene, you can specify the directory to read the tiles from. Alternatively, if you're trying CesiumForUnreal you can provide the root tileset json file. |
| <code>&#x2011;clientauthpubkey=</code><i>public_key</i> | Specify a client authorization public key to require clients to present a client authorization token before being allowed to use the client API.  Overrides the key set by the [PROJECTAIRSIM_CLIENT_AUTH_PUBKEY](#environment_variables) environment variable. |

The below simulation parameters can also be changed through the comand line:

| Switch | Value | Default | Description |
| ------ | ----- | ----- | ----- |
| <code>&#x2011;topicsport</code> | integer | 8989 | TCP port for pub-sub client connection (e.g. <code>&#x2011;topicsport=8989</code>)|
| <code>&#x2011;servicesport</code> | integer | 8990 | TCP port for req-resp client connection (e.g. <code>&#x2011;servicesport=8990</code>)|

**Note**: The port values must be different from one another.


# Environment Variables

Project AirSim supports the following environment variables:

| Environment Variable | Description |
| -------------------- | ----------- |
| <code>PROJECTAIRSIM_CLIENT_AUTH_PUBKEY</code> | Client authorization token public key

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