Native Plugins

Unity has extensive support for native Plugins, which are libraries of native code written in C, C++, Objective-C, etc. Plugins allow your game code (written in Javascript or C#) to call functions from these libraries. This feature allows Unity to integrate with middleware libraries or existing C/C++ game code.

In order to use a native plugin you firstly need to write functions in a C-based language to access whatever features you need and compile them into a library. In Unity, you will also need to create a C# script which calls functions in the native library.

The native plugin should provide a simple C interface which the C# script then exposes to other user scriptsA piece of code that allows you to create your own Components, trigger game events, modify Component properties over time and respond to user input in any way you like. More info
See in Glossary. It is also possible for Unity to call functions exported by the native plugin when certain low-level renderingThe process of drawing graphics to the screen (or to a render texture). By default, the main camera in Unity renders its view to the screen. More info
See in Glossary events happen (for example, when a graphics device is created), see the Native Plugin Interface page for details.

Example

A very simple native library with a single function might have source code that looks like this:

    float FooPluginFunction () { return 5.0F; } 

To access this code from within Unity, you could use code like the following:

    using UnityEngine;
    using System.Runtime.InteropServices;

    class SomeScript : MonoBehaviour {

       #if UNITY_IPHONE
   
       // On iOS plugins are statically linked into
       // the executable, so we have to use __Internal as the
       // library name.
       [DllImport ("__Internal")]

       #else

       // Other platforms load plugins dynamically, so pass the name
       // of the plugin's dynamic library.
       [DllImport ("PluginName")]
    
       #endif

       private static extern float FooPluginFunction ();

       void Awake () {
          // Calls the FooPluginFunction inside the plugin
          // And prints 5 to the console
          print (FooPluginFunction ());
       }
    }

Note that when using Javascript you will need to use the following syntax, where DLLName is the name of the plugin you have written, or “__Internal” if you are writing statically linked native code:

    @DllImport (DLLName)
    static private function FooPluginFunction () : float {};

Creating a Native Plugin

In general, plugins are built with native code compilers on the target platform. Since plugin functions use a C-based call interface, you must avoid name mangling issues when using C++ or Objective-C.

Further Information

• Native Plugin Interface (this is needed if you want to do rendering in your plugin)
• Mono Interop with native libraries
• P-invoke documentation on MSDN