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Announcing UnityXNA – XNA Inside Unity3D

July 7th, 2012 | Posted by mvi in Unity3D | UnityXNA | XNA
Disclaimer:
I’ve received a lot of emails asking if UnityXNA is suitable for porting an existing XNA game to Unity. The short answer is: it is, if you’re prepared to do the leg work yourself. UnityXNA only implements the bare minimum of the XNA API in order to get the Platformer sample working. If your project uses any parts of the XNA API that the Platformer sample does not, you will need to add support for this yourself. Due to personal time constraints and the nature of this project as a tech demo only, I can offer no support for UnityXNA. Source code is provided for the curious and as a nice starting point for more serious emulation of XNA in Unity.

I had a theory that it would be straightforward to get XNA games running in Unity3D so I decided to give it a go.

This is a proof of concept showing the Platformer XNA sample running inside Unity3D. Zero code changes have been made to the original game code. Using a mixture of new code and some code from MonoXNA I’ve implemented XNA emulation by having a game object with a script attached run an XNA game performing updates and drawing.

You can see the game in your browser here and download the source here.

Implemented so far:

  1. Basic game loop and GameTime calculation.
  2. ContentManager loads Texture2Ds, SoundEffects and Songs, each wrapping the relevant Unity3D object.
  3. SpriteBatch Draw implemented using a draw queue, specifically created for the purpose. Currently supports colour tinting, source rectangles, and sprite effect flip modes.
  4. SpriteBatch DrawString has limited support, rendering the text in the correct position and with the correct colour.
  5. Support for playing Songs through MediaPlayer and playing SoundEffects
  6. KeyboardStates emulated for a limited set of keys which are mapped from their XNA values to Unity3D KeyCodes.
  7. Zero code changes to the game needed to run Platformer sample

Known issues, immediate areas for improvement:

  1. SpriteFont is not supported, all DrawStrings render with the default GUI Label font.
  2. Frame rate is currently vsync’d at 60 frames per second. When vsync is disabled GameTime is not calculated correctly.
  3. Windows Media Audio (.wma) is not supported by Unity3D, so I’ve converted the sample audio files to Ogg Vorbis (.ogg).
  4. Keyboard input is currently limited to a small set of keys, more mappings between XNA Keys and Unity3D KeyCodes need creating.
  5. Mouse, gamepad and touch input are not currently implemented.

Proof of concept live in browser            Download source code at GitHub

Edit: This post has had some overwhelming support, so thanks for all the tweets and mentions. I have made the full source code available on GitHub and I think it provides a great starting point if you have a finished 2D XNA game which you want to port to Unity3D and you’re prepared to spend a few weeks (instead of months) on it.  However as a proof of concept it has achieved my original goal, I’m afraid I can offer no support to XNA projects wishing to port to Unity3D.

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