The Challenge of Building Augmented Reality Games In The Real World

InnAR Wars Splash Image - B

Last week I submitted the prototype build of my latest augmented reality project, InnAR Wars, to Google’s Build a Tango App Contest. It’s an augmented reality multiplayer space RTS built for Google’s Tango tablet that utilizes the environment around you as a game map. The game uses the Tango’s camera and Area Learning capabilities to superimpose an asteroid-strewn space battlefield over your real-world environment. Two players holding Tangos walk around the room hunting for each other’s bases while sending attack fleets at the other player’s structures.

Making InnAR Wars fun is tricky because I essentially have no control over the map. The battlefield has to fit inside the confines of the real-world environment the tablets are in. Using the Tango’s Area Learning capabilities with the positions of players, I know the rough size of the play area. With this information I adjust the density of planetoids and asteroids based on the size of the room. It’s one small way I can make sure the game at least has an interesting number of objects in the playfield regardless of the size of the area. As you can see from the videos in this post, it’s already being played in a variety of environments.

This brings up the biggest challenge of augmented reality games–How do you make a game fun when you have absolutely no control over the environment in which it’s played? One way is to require the user to set up the play space as if she were playing a board game. By using Tango’s depth camera, you could detect the shapes and sizes of objects on a table and use those as the playfield. It’s up to the user to set it up in a way that’s fun–much like playing a tabletop war game.

For the final release, I’m planning on using Tango’s depth camera to figure out where the room’s walls, ceilings, and floors are. Then I can have ships launch from portals that appear to open on the surfaces of the room. Dealing with the limited precision and performance of the Tango depth camera along with the linear algebra involved in plane estimation is a significant challenge. Luckily, there are a few third-party solutions for this I’m evaluating.

Especially when looking at augmented reality startups’ obligatory fake demo videos, the future of AR gaming seems exciting. But the practical reality of designing a game to be played in reality–which is itself rather poorly designed–can prevent even the most amazing technology from enabling great games. It’s probably going to take a few more hardware generations to not only make the technology usable, but also develop the design language to make great games that work in AR.

If you want to try out the game, I’ll have a few Tangos on hand at FLARB’s VRLA Summer Expo table. Stop by and check it out!

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.


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.

My Week With Project Tango

A few weeks back I got into Google’s exclusive Project Tango developers program. I’ve had a Tango tablet for about a week and have been experimenting with the available apps and Unity3D SDK.

Project Tango uses Movidius’ Myriad 1 Vision Processor chip (or “VPU”), paired with a depth camera not too unlike the original Kinect for the XBOX 360. Except instead of being a giant hideous block, it’s small enough to stick in a phone or tablet.

I’m excited about Tango because it’s an important step in solving many of the problems I have with current Augmented Reality technology. What issues can Tango solve?


First, the Tango tablet has the ability to determine the tablet’s pose. Sure, pretty much every mobile device out there can detect its precise orientation by fusing together compass and gyro information. But by using the Tango’s array of sensors, the Myriad 1 processor can detect position and translation. You can walk around with the tablet and it knows how far and where you’ve moved. This makes SLAM algorithms much easier to develop and more precise than strictly optical solutions.

Also, another problem with AR as it exists now is that there’s no way to know whether you or the image target moved. Rendering-wise, there’s no difference. But, this poses a problem with game physics. If you smash your head (while wearing AR glasses) into a virtual box, the box should go flying. If the box is thrown at you, it should bounce off your head–big distinction!

Pose and position tracking has the potential to factor out the user’s movement and determine the motion of both the observer and the objects that are being tracked. This can then be fed into a game engine’s physics system to get accurate physics interactions between the observer and virtual objects.


Anyway, that’s kind of an esoteric problem. The biggest issue with AR is most solutions can only overlay graphics on top of a scene. As you can see in my Ether Drift project, the characters appear on top of specially designed trading cards. However, wave your hand in front of the characters, and they will still draw on top of everything.

Ether Drift uses Vuforia to superimpose virtual characters on top of trading cards.

Ether Drift uses Vuforia to superimpose virtual characters on top of trading cards.

With Tango, it is possible to reconstruct the 3D geometry of your surroundings using point cloud data received from the depth camera. Matterport already has an impressive demo of this running on the Tango. It allows the user to scan an area with the tablet (very slowly) and it will build a textured mesh out of what it sees. When meshing is turned off the tablet can detect precisely where it is in the saved environment mesh.

This geometry can possibly be used in Unity3D as a mesh collider which is also rendered to the depth buffer of the scene’s camera while displaying the tablet camera’s video feed. This means superimposed augmented reality characters can accurately collide with the static environment, as well as be occluded by real world objects. Characters can now not only appear on top of your table, but behind it–obscured by a chair leg.


Finally, this solves the challenge of how to properly light AR objects. Most AR apps assume there’s a light source on the ceiling and place a directional light pointing down. With a mesh built from local point cloud data, you can generate a panoramic render of where the observer is standing in the real world. This image can be used as a cube map for Image-based lighting systems like Marmoset Skyshop. This produces accurate lighting on 3D objects which when combined with environmental occlusion makes this truly a next generation AR experience.


The first thing I did with the Unity SDK is drop the Tango camera in a Camera Birds scene. One of the most common requests for Camera Birds was to be able to walk through the forest instead of just rotating in place. It took no programming at all for me to make this happen with Tango.

This technology still has a long way to go–it has to become faster and more precise. Luckily, Movidius has already produced the Myriad 2, which is reportedly 3-5X faster and 20X more power efficient than the chip currently in the Tango prototypes. Vision Processing technology is a supremely nerdy topic–after all it’s literally rocket science. But it has far reaching implications for wearable platforms.

Samsung Gear VR Development Challenges with Unity3D

As you may know, I’m a huge fan of Oculus and Samsung’s Gear VR headset. The reason isn’t about the opportunity Gear VR presents today. It’s about the future of wearables–specifically of self-contained wearable devices. In this category, Gear VR is really the first of its kind. The lessons you learn developing for Gear VR will carry over into the bright future of compact, self-contained, wearable displays and platforms. Many of which we’ve already started to see.

The Gear VR in the flesh (plastic).

The Gear VR in the flesh (plastic).

Gear VR development can be a challenge. Rendering two cameras and a distortion mesh on a mobile device at a rock solid 60fps requires a lot of optimization and development discipline. Now that Oculus’ mobile SDK is public and having worked on a few launch titles (including my own original title recently covered in Vice), I figured I’d share some Unity3D development challenges I’ve dealt with.


The biggest challenge with making VR performant on a mobile devices is throttling due to heat produced by the chipset. Use too much power and the entire device will slow itself down to cool off and avoid damaging the hardware. Although the Note 4 approaches the XBOX 360 in performance characteristics, you only have a fraction of its power available. This is because the phone must take power and heat considerations in mind when keeping the CPU and GPU running at full speed.

With the Gear VR SDK you can independently tell the device how fast the GPU and CPU should run. This prevents you from eating up battery when you don’t need the extra cycles, as well as tune your game for performance at lower clock speeds. Still, you have to be aware of what types of things eat up GPU cycles or consume GPU resources. Ultimately, you must choose which to allocate more power for.


The obvious optimization is lowering graphical detail. Keep your polycount under 50k triangles. Avoid as much per pixel and per vertex processing as possible. Since you have tons of RAM but relatively little GPU power available–opt for more texture detail over geometry. This includes using lightmaps instead of dynamic lighting. Of course, restrict your usage of alpha channel to a minimum–preferably for quick particle effects, not for things that stay on the screen for a long period of time.

Effects you take for granted on modern mobile platforms, like skyboxes and fog, should be avoided on Gear VR. Find alternatives or design an art style that doesn’t need them. A lot of these restrictions can be made up for with texture detail.

A lot of standard optimizations apply here–for instance, use texture atlasing and batching to reduce draw calls. The target is under 100 draw calls, which is achievable if you plan your assets correctly. Naturally, there are plenty of resources in the Asset Store to get you there. Check out Pro Draw Call Optimizer for a good texture atlasing tool.


There are less obvious optimizations you might not be familiar with until you’ve gone to extreme lengths to optimize a Gear VR application. This includes removing as many Update methods as possible. Most update code spent waiting for stuff to happen (like an AI that waits 5 seconds to pick a new target) can be changed to a coroutine that is scheduled to happen in the future. Converting Update loops to coroutines will take the burden of waiting off the CPU. Even empty Update functions can drain the CPU–death by a thousand cuts. Go through your code base and remove all unnecessary Update methods.

As in any mobile game, you should be pooling prefabs. I use Path-o-Logical’s PoolManager, however it’s not too hard to write your own. Either way, by recycling pre-created instances of prefabs, you save memory and reduce hiccups due to instantiation.


There’s nothing really new here to most mobile developers, but Gear VR is definitely one of the bigger optimization challenges I’ve had in recent years. The fun part about it is we’re kind of at the level of Dreamcast-era poly counts and effects but using modern tools to create content. It’s better than the good old days!

It’s wise to build for the ground up for Gear VR than to port existing applications. This is because making a VR experience that is immersive and performant with these parameters requires all disciplines (programming, art, and design) to build around these restrictions from the start of the project.

My Week with the Ouya

I’ve been skeptical of the Ouya since the beginning. Who would want to play mobile games scaled up on a TV with a box that’s about as powerful as a mid-range Android phone? Last year’s smashing Kickstarter success and resultant investor stampede was a mystery to me. Criticism of Ouya’s launch has been harsh. For a mere $99, I had to see if this microconsole ‘revolution’ is going to take off.

My Ouya

My Ouya

The console itself is a nice piece of industrial design–except for the fact that the vent is on the bottom. There also are shielding issues forcing some users to lay the box on its side or position it away from cabling to prevent interference with Bluetooth and WiFi. Contrasting Ouya’s sleek form factor is a cheap looking controller with no obvious way to put batteries in. At $99, you have to cut corners somewhere.

Setting up the Ouya is easy. It requires the creation of an Ouya account and a credit card link before playing anything. Some are complaining about this, but there’s no point in getting users on the platform if they aren’t going to pay. Making sure every user is billable and ready to buy stuff is a top priority for Ouya.

Despite having to create user accounts, Ouya appears to have no social network based around them. There aren’t any friends lists, achievements, or leaderboards. This is a glaring omission. Ouya’s somewhat unwieldy catalog is organized by curated arrays of games from celebrity editors and lists sorted by genre. At the very least, I’d like to see what some of my friends are playing.

What about the games? Frankly, they are atrocious. With over 100 launch titles, this is to be expected. Ouya’s games include half-baked ports from mobile (some don’t even bother to change the screen to landscape!), suspect exclusives, and tragically hip indie games about abused children.

As I dove deep into the Ouya catalog, I actually began to enjoy the experience. The diversity of games is charming. Plus, I’m a big connoisseur of b-movies and the Ouya feels like the MST3k of consoles. Blowing up games originally built for a 4-inch screen on my 60-inch TV really magnifies polish issues and sub-par graphics. Seeing just how bad some of these games are can be hilarious. However, I’m not quite sure that’s what Ouya had in mind.

Where Ouya shines is playing mobile game ports that originally had virtual buttons and d-pads. Games like Gunslugs and the unusually polished Ice Rage play MUCH better with physical controls. My current obsession is Ravensword: Shadowlands. Despite having bought it on the iPad last year, I purchased the Ouya version and have been ironically enjoying it as a PS2-looking Roger Corman-esque Z-grade Skyrim. It’s hilariously unpolished, absurdly ambitious, and infinitely more playable with a joypad despite the game being somewhat incompetently designed.

Ouya’s biggest flaw is the business model. All games are a hybrid of premium and f2p with a timed demo period. I learned way back in the feature phone era that demos are death for casual games. With an constant stream of content and bite-sized gameplay, users get their fill of your title for free and move on to the next demo. Forcing this model on developers is a major mistake. It’s the hallmark of a team clueless as to how to build a thriving ecosystem. If your mantra is “free the games,” then free the business model too. Straight f2p and video previews for premium titles is a much better option.

A lot of these early problems are to be expected from a company launching its first consumer electronics product so quickly. Also, people seem to have unrealistic expectations for a $99 box. It remains to be seen if the emerging category of microconsoles will be a market of any significance. Perhaps Ouya can break off some of their war chest for quality exclusive titles, or else they are doomed to drown in a sea of similar devices.

Native Code is Dead

Although Android has a larger market share when you count it by pure number of devices and users, iOS still dominates monetization. Research I did earlier this year about apathetic Android users still rings true. However, vast improvements in Android as an OS and Google Play as a way to monetize apps are changing this. Not to mention changes to the new iOS 6 App Store are making app discovery even more difficult on Apple devices. A lot of developers are grumbling about their fortunes on iOS and are looking elsewhere.

Platforms are volatile. Five years ago, Facebook was the ultimate destination for game developers. Now it’s a ghost town. iOS is the hot ticket now, but Android is becoming increasingly competitive. As a developer you need to be prepared to move platforms in an instant. For this reason, native code is dead.

Using a solution such as Unity3D, Flash, or HTML5 allows you to easily move apps from one device to another. Or, from mobile to the Web. Or, from Web to desktop. You get the idea. It’s true that each one of these solutions has tradeoffs in features or performance to accomplish frictionless cross-platform porting. However, most studios can’t afford to double their engineering staff to multiply the amount of platforms they deploy on.

If you’re starting a new project from scratch, you have to consider your cross-platform options:


As one of the (very few) detractors said of my recent GDCO 2012 presentation on Unity3D: “This guy was a bigger Unity fan-boy than the company would have been.” It’s true! I am a self-declared Unity3D zealot. My experience moving between platforms has been incredibly easy. You can check this older post on the process I went through to bring Brick Buddies to Android. Unity3D has issues, but it’s the best solution I’ve found yet.


I’ve not used Corona myself, but did research it a bit when deciding which platform to hang my hat on. I know other developers who have created very successful apps with it. The major drawbacks are it uses Lua as its scripting language and it still doesn’t allow native code extensions. Yeah, I know I said native was dead–but not totally dead. I occasionally have to write native code plug-ins for Unity3D to access parts of a platform’s API that aren’t abstracted in Unity itself. This is a critical feature. Also, Corona can’t be used on the web or desktop platforms.


Flash has a tragic branding problem. The declaration of mobile Flash’s death doesn’t mean Flash is dead on mobile. This means the browser plug-in on Android is defunct. Good riddance. Flash made the mobile browsing experience on Android unusable.

Adobe has stepped their game up with Flash’s iOS and Android exporters. The packager allows Flash projects to be exported as apps on the target device. Flash’s CS5 exporter was atrocious, but I’ve seen some impressive work with the latest version. Flash even supports native code extensions. Adobe’s extortionate demands for revenue share mean Flash is out of the running for me if I intend to use their more advanced features. Otherwise, it is a superior option over Corona.


For game development, HTML5 is insane. If you really want to give it a shot, there are some relatively performant libraries such as impact.js that might help you out. I don’t recommend it. HTML5 isn’t much of a standard, needing a lot of workarounds for various browsers. Not to mention its horrible performance on mobile browsers. You just can’t win.

For non-game GUI-based apps (like Yelp or Evernote) HTML5 makes a lot of sense. PhoneGap/Cordova makes this possible by providing a framework for running HTML5/CSS/JS based applications inside a mobile web view and packaged as a native app. Coming from a native code background, constructing interfaces in HTML5/CSS seems absolutely insane. Friends don’t let friends write HTML/CSS. It should remain purely the output of tools such as Handheld Designer. HTML/CSS is becoming the Assembly Language of the web–it’s good to know, but hopefully you’ll never have to touch it.


There are plenty of other options I haven’t mentioned: Moai, Marmalade, Titanium Studio, UDK, and the list goes on. The important thing is to research your platform independent option and find what’s best for you. For games, I’m biased towards Unity–but other options are just as valid…I guess. Obviously there are applications for which native code will always be the solution. Yet, for the incredible glut of dying console game studios “pivoting to mobile,” this is an increasingly remote option.

Kakao is the new Asian mobile gaming powerhouse

Kakao has leveraged their insanely popular mobile group messaging app, Kakao Talk, to launch a social gaming network called Game Center in Korea. This is similar to Tencent’s strategy of using their Chinese instant messaging network, QQ, to drive traffic to f2p PC games. Yet in the West, Apple’s iMessage seems to have killed off most group messaging startups, and the only one to pursue a gaming strategy released a tower defense game based on Shannon Tweed. No, really.

Kakao has successfully commissioned established game developers to produce high quality games for Game Center. The slickly produced Match-3 game, Anipang, recently rose to the top of the Korean App Store due to its use of Kakao Talk as a viral messaging channel. (It’s also available for Android) Encouraging users to message friends in order to get extra plays, Anipang uses social news update notifications similar to the early days of Facebook games to drive reach. Korean friends of mine have deleted the app from their iPhones to avoid the onslaught of game messages–reminiscent of the bad old days of “Lost Sheep” Farmville spam. Regardless, Kakao has mined a passionate and highly monetizable social network of gamers from Kakao Talk.

With over 55 million users, Kakao may eclipse the size of DeNA’s Mobage platform. It remains to be seen what their plans for the US are. Although Game Center will probably have to be renamed before it launches in the West. I hear Apple can be quite litigious when it comes to their intellectual property.

Come to my session next week at Austin GDC

By the way…On Wednesday, October 10th at 5:35 PM at Austin GDC come see my talk on cross-platform Unity3D mobile games development. Hey, it’s only 25 minutes long. How bad can it be?