Unity3D
Unity is a videogame engine and one of the most popular currently in existence. Its free for use although not open source and will cost you after a certain amount of revenue so that's something you may want to take into account.
Installing
To start using Unity3D in Linux you require to download the .deb file from the developer's page. Afterwards you can use a package manager such as gdebi to install the application.
Once installed, you need to register yourself as a member of the Unity community and select the Personal License. After that you'll be shown the following screen in which you can create and manage your projects.
Once installed, you need to register yourself as a member of the Unity community and select the Personal License. After that you'll be shown the following screen in which you can create and manage your projects.