How To Support Gear VR and Google Cardboard In One Unity3D Project

Google Cardboard is a huge success. Cardboard’s userbase currently dwarfs that of Gear VR. Users, investors, and collaborators who don’t have access to Gear VR often ask for Cardboard versions of my games. As part of planning what to do next with Caldera Defense, I decided to create a workflow to port between Gear VR and Cardboard.

Always keep a Cardboard on me at ALL TIMES!

I used my VR Jam entry, Duck Pond VR, as a test bed for my Unity3D SDK switching scripts. It’s much easier to do this on a new project. Here’s how I did it:

Unity 4 vs. Unity 5

Google Cardboard supports Unity 4 and Unity 5. Although Oculus’ mobile SDK will technically work on Unity 5, you can’t ship with it because bugs in the current version of Unity 5 cause memory leaks and other issues on the Gear VR hardware. Unity is working on a fix but I haven’t heard any ETA on Gear VR support in Unity 5.

This is a bummer since the Cardboard SDK for Unity 5 supports skyboxes and other features in addition to the improvements Unity 5 has over 4. Unfortunately you’re stuck with Unity 4 when making a cross-platform Gear VR and Cardboard app.

Dealing With Cardboard’s Lack of Input

Although Gear VR’s simplistic touch controls are a challenge to develop for, the vast majority of Cardboards have no controls at all! Yes, Google Cardboard includes a clever magnetic trigger for a single input event. Yet, the sad fact is most Android devices don’t have the necessary dock connector to use this.

You have a few other control options that are universal to all Android devices: the microphone and Bluetooth controllers. By keeping the microphone open, you can use loud sounds (such as a shout) to trigger an action. You can probably use something like the Pitch Detector plug-in for this. Or, if your cardboard has a head strap for hands-free operation, you can use a Bluetooth gamepad for controls.

Because of this general lack of input, many Cardboard apps use what I call “stare buttons” for GUIs. These are buttons that trigger if you look at them long enough. I’ve implemented my own version. The prefab is here, the code is here. It even hooks into the new Unity UI event system so you can use it with my Oculus world space cursor code.

Gear VR apps must be redesigned to fit within Cardboard’s constraints. Whether it’s for limited controls or the performance constraints of low end devices. Most of my Cardboard ports are slimmed down Gear VR experiences. In the case of Caldera Defense, I’m designing a simplified auto-firing survival mode for the Cardboard port. I’ll merge this mode back into the Gear VR version as an extra game mode in the next update.

Swapping SDKs

This is surprisingly easy. You can install the Cardboard and Gear VR SDKs in a single Unity project with almost no problems. The only conflict is they both overwrite the Android manifest in the plugin folder. I wrote an SDK swapper that lets you switch between the Google Cardboard and Oculus manifests before you do a build. You can get it here. This editor script has you pick where each manifest file is for Cardboard and Gear VR and will simply copy over the appropriate file to the plugin folder. Of course for iOS Cardboard apps this isn’t an issue.

Supporting Both Prefabs

Both Oculus and Cardboard have their own prefabs that represent the player’s head and eye cameras. In Caldera Defense, I originally attached a bunch of game objects to the player’s head to use for traces, GUI positioning, HUDs, and other things that need to use the player’s head position and orientation. In order for these to work on both Cardboard and Oculus’ prefabs, I placed all objects attached to the head on another prefab which is attached to the Cardboard or Oculus’ head model at runtime.

Wrapping Both APIs

Not only do both SDK’s have similar prefabs for the head model, they also have similar APIs. In both Cardboard and Oculus versions, I need to refer to the eye and head positions for various operations. To do this, I created a simple class that detects which prefab is present in the scene, and grabs the respective class to wrap the eye position reference around. The script is in the prefab’s package.

Conclusion

For the final step, I made separate Cardboard versions of all my relevant Gear VR scenes which include the Cardboard prefabs and modified gameplay and interfaces. If no actual Oculus SDK code is in any of the classes used in the Cardboard version, the Oculus SDK should be stripped out of that build and you’ll have no problem running on Cardboard. This probably means I really need to make an Oculus and Cardboard specific versions of that CameraBody script.

The upcoming Unity 5.1 includes native Oculus support which may make this process a bit more complicated. Until then, these steps are the best way I can find to support both Cardboard and Gear VR in one project. I’m a big fan of mobile VR, and I think it’s necessary for any developer at this early stage of the market to get content out to as many users as possible.

Why I’m All In On Mobile VR

Last month I released Caldera Defense, a Virtual Reality tower defense game on Gear VR. This is the second Gear VR title I’ve worked on, and the first I’ve built and published from the ground up. (Not including my Oculus Mobile VR Jam submission) Caldera Defense is a free early access demo–basically a proof of concept of the full game–and the reaction has been great. Thousands of people have downloaded, rated, and given us valuable feedback. We’re busy incorporating it into the first update.

Caldera Defense featured on the Gear VR store

Originally I planned to use this as a demo to fund an expanded PC and Morpheus launch version of the game with greatly improved graphics, hours of gameplay, and additional features such as multiplayer and second-screen options.

However, pitching even a modestly budgeted console and PC VR game experience to publishers, or even the platforms themselves, is a tough sell. I’m sure at E3 next month we will see all sorts of AAA VR announcements. Yet, many traditional funding avenues for games remain skeptical of the opportunity VR presents.

Since the Caldera project began last year, mobile VR has morphed into a unique opportunity. With over a million Google Cardboards in the wild and new versions of the Gear VR headset in retail stores worldwide, there will be millions of mobile VR users before there’s comparable numbers on Oculus desktop, Vive, and Morpheus.

Is it possible that mobile VR will be a viable business before it is on PC and consoles? Most of my colleagues are skeptical. I’m not.

The economics work out. Due to the mobile nature of the experience, games and apps for these platforms tend towards the bite-sized. This greatly reduces the risk of mobile VR since assets optimized for mobile are simpler and casual VR experiences require less content to be built overall.

I can make a dozen mobile VR minimum viable products for the same budget of one modestly scoped Morpheus experience. From these MVPs I can determine what types of content gains the most traction with VR users and move in that direction. I can even use this data to guide development of larger AAA VR experiences later.

By this time next year it will be possible to monetize these users significantly, whether through premium content or advertising. It may be more valuable to collect a lot of eyeballs in mobile VR than breaking even on a multi-million dollar AAA launch tile. As we’ve seen in the past, acquiring a huge audience of mobile players can lead to tremendous revenue streams.

Being on the Oculus desktop, Vive, or Sony’s Morpheus deck at launch is an enormous opportunity. In fact, I’m still searching for ways to produce the console and desktop version of Caldera Defense. However, if you lack the capital to produce at that scale, smaller mobile projects are much easier to bootstrap and the upside is huge.