Native plug-ins

Unity supports native plug-insA set of code created outside of Unity that creates functionality in Unity. There are two kinds of plug-ins you can use in Unity: Managed plug-ins (managed .NET assemblies created with tools like Visual Studio) and Native plug-ins (platform-specific native code libraries). More info
See in Glossary, which are libraries of native code you can write in languages such as C, C++, and Objective-C. Plug-ins allow the code you write in C# to call functions from these libraries. This feature allows Unity to integrate with middleware libraries or existing C/C++ code.

The native plug-inA platform-specific native code library that is created outside of Unity for use in Unity. Allows you can access features like OS calls and third-party code libraries that would otherwise not be available to Unity. More info
See in Glossary provides a simple C interface, which the C# script then exposes to your other 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. Unity can also call functions that the native plug-in exports 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 you create a graphics device). See Low-level native plug-in interface for more information.

For an example of a native plugin, see Native Renderer Plugin.

Using a native plug-in

To use a native plug-in:

1. Write functions in a C-based language to access the features you need.
2. Compile them into a library.
3. In Unity, create a C# script that calls functions in the native library.

You build native plug-ins with native code compilers on the target platform. Because plug-in functions use a C-based call interface, you must declare the functions with C linkage to avoid name mangling issues.

Example

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

float ExamplePluginFunction () { return 5.0F; }

To access this code from within Unity, use the following C# script:

using UnityEngine;
using System.Runtime.InteropServices;

class ExampleScript : 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 ExamplePluginFunction ();

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

Further information

You can learn more about using native plugins to interact with third-party code libraries, including how you can implement rendering in your plug-in, with the following pages:

• Low-level native plug-in interface
• Mono Interop with native libraries
• P-invoke documentation on MSDN