For the past decade, Unity3D has lacked official GNU/Linux support. Some tenacious users have worked around this with WINE, with varying degrees of success. Fortunately for us GNU/Linux users, Unity3D is now officially available and support is provided in the new Linux forums. To improve the situation further, Arcadia is also compatible with this new GNU/Linux build. I’ll cover here how to get things up and running.

My setup

I’m currently running Arch Linux and using the proprietary nVidia drivers for my two GTX 670MX cards. This should work on just about any distro, but you should be sure to use the latest graphics drivers you can; Unity is undoubtedly heavy.

Installing Unity3D

To get going, hop on over to the release thread and navigate to the last post. If you’re on a Debian-based distribution, you’ll be happy to just find a deb you can install. For the rest of us, there’s an awkwardly unconventional shell script we can run, which also comes with some binary data embedded in it (~2GB in size). Fair warning.

You should pull down the latest; the commands below are what I used and there may be a newer version for you. Note that, if you read the script, root is required for the use of a chromium suid sandbox. Fair warning.

$ installer=unity-editor-installer-5.3.1f1+20160106.sh
$ wget http://download.unity3d.com/download_unity/linux/$installer
$ chmod +x ./$installer
$ su - -c "cd $PWD ; ./$installer"

The dependencies can also be found in the release thread and are left to you to figure out.

Issues on startup

There’s an existing issue where Unity, once installed, requires some directories which it’s apparently unable to create. To be safe, before running Unity, you should run:

$ mkdir -p ~/.local/share/unity3d/Unity

Also, don’t forget to install npm, which crept up on me silently. Unity won’t complain about not having it, the start screen just won’t show anything.

Running Unity

Assuming all went well, you should be able to start up Unity, sign in, and create some new projects.

$ ./unity-editor-5.3.1f1/Editor/Unity

From here, continue on with your normal Unity workflow and report all bugs, crashes, etc to the Unity forums.

What is Arcadia?

Arcadia is a new project which integrates Clojure CLR (Clojure on .NET) with Unity. This allows not only for writing Unity components, logic, etc in Clojure, it also allows for integrating a Clojure REPL into the Unity editor for programmatic manipulation of the scene. We’ll see, briefly, what I mean.

Installing Arcadia

To install Arcadia, just clone it into the Assets directory of your current project.

$ cd ~/projects/my-unity-game/Assets
$ git clone -b develop https://github.com/arcadia-unity/Arcadia.git

If things don’t work out of the box, you can take a look at their provided Getting Started wiki page.

Using the REPL

Once Arcadia is installed, we can spin up a Clojure REPL and try interacting with the Unity editor.

$ cd ~/projects/my-unity-game
$ ruby ./Assets/Arcadia/Editor/repl-client.rb

Once you’re in the REPL, we can verify everything is sane.

user=> (+ 1 41)
42

Now let’s interact with the Unity editor.

user=> (def cube (create-primitive :cube))
#'user/cube

If you look back into the Unity window, you’ll find that the cube you created is now part of the scene. This means you can use Clojure, in a REPL, to programmatically manipulate your scene before even running the game. A possible use for this would be creating procedural content before hand, instead of at run-time.

Perhaps the most useful aspect of the REPL here is how it can automate work for you, which would otherwise involve the mouse in the editor. I can select any object in the scene, with my mouse, and then move over to the REPL can gain access to it.

user=> (import Selection)
user=> (Selection/activeObject)
#<GameObject Plane (UnityEngine.GameObject)>

If I select multiple objects, I can get a sequence of all of them in Clojure.

user=> (Selection/objects)
(#<GameObject Plane (UnityEngine.GameObject)> #<GameObject Water (UnityEngine.GameObject)>)

With this sequence, I could do any number of operations, from renaming, resizing, parenting, destroying, adding or removing components, etc.

Naming Clojure files

One aspect on which I want to touch is just how finicky Arcadia can be with namespacing and file paths. If my project is called ninjakitten and my file is called milk.clj, the path should be Assets/ninjakitten/milk.clj and the corresponding Clojure namespace should be:

(ns ninjakitten.milk
  (:use arcadia.core))

Helpful Arcadia resources

Arcadia has a Gittr channel, a mailing list, and an IRC channel on Freenode #arcadiaunity. Aside from that, there are a couple of great demos on Youtube, here and here.