Version: 2019.1 (switch to 2018.4
Native plug-ins
Low-level native plug-in interface
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Building plug-ins for desktop platforms

This page describes native code plug-ins for desktop platforms (Windows/Mac OS X/Linux).

Building a plug-in for Mac OS X

On Mac OSX, 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
are deployed as bundles. You can create the bundle project with XCode by selecting File->NewProject… and then selecting Bundle -> Carbon/Cocoa Loadable Bundle (in XCode 3) or OS X -> Framework & Library -> Bundle (in XCode 4)

If you are using C++ (.cpp) or Objective-C (.mm) to implement the plug-in then you must ensure the functions are declared with C linkage to avoid name mangling issues.

extern "C" {
  float FooPluginFunction ();
}

Building a plug-in for Windows

Plug-ins on Windows are DLL files with exported functions. Practically any language or development environment that can create DLL files can be used to create plug-ins. As with Mac OSX, you should declare any C++ functions with C linkage to avoid name mangling issues.

Building a plug-in for Linux

Plug-ins on Linux are .so files with exported functions. These libraries are typically written in C or C++, but any language can be used. As with the other platforms, you should declare any C++ functions with C linkage in order to avoid name mangling issues.

32-bit and 64-bit libraries

The issue of needing 32-bit and/or 64-bit plug-ins is handled differently depending on the platform.

Windows and Linux

On Windows and Linux, plug-ins can be managed manually (e.g, before building a 64-bit player, you copy the 64-bit library into the Assets/Plugins folder, and before building a 32-bit player, you copy the 32-bit library into the Assets/Plugins folder) OR you can place the 32-bit version of the plug-in in Assets/Plugins/x86 and the 64-bit version of the plug-in in Assets/Plugins/x86_64. By default the editor will look in the architecture-specific sub-directory first, and if that directory does not exist, it will copy plug-ins from the root Assets/Plugins folder instead.

Note that for the Universal Linux build, you are required to use the architecture-specific sub-directories (when building a Universal Linux build, the Editor will not copy any plug-ins from the root Assets/Plugins folder).

Mac OS X

For Mac OS X, you should build your plug-in as a universal binary that contains both 32-bit and 64-bit architectures.

Using your plug-in from C#

Once built, the bundle should be placed in the Assets->Plugins folder (or the appropriate architecture-specific sub-directory) in the Unity project. Unity will then find it by name when you define a function like this in the C# script:-

[DllImport ("PluginName")]
private static extern float FooPluginFunction ();

Please note that PluginName should not include the library prefix nor file extension. For example, the actual name of the plug-in file would be PluginName.dll on Windows and libPluginName.so on Linux. Be aware that whenever you change code in the plug-in you will need to recompile 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
in your project or else the plug-in will not have the latest compiled code.

Deployment

For cross platform plug-ins you must include the .bundle (for Mac), .dll (for Windows), and .so (for Linux) files in the Plugins folder. No further work is then required on your side - Unity automatically picks the right plug-in for the target platform and includes it with the player.

Examples

Simplest plug-in

This plug-in project implements only some very basic operations (print a number, print a string, add two floats, add two integers). This example may be helpful if this is your first Unity plug-in. The project can be found here and includes Windows, Mac, and Linux project files.

Rendering from C++ code

An example multiplatform plug-in that works with multithreaded 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
in Unity can be found on the native plug-in interface page.

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Native plug-ins
Low-level native plug-in interface