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.

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.

The Coming Public Point Cloud

One of the most important elements of Augmented Reality is the ability to seamlessly mesh 3D graphics with the real world.  Current AR technology simply overlays graphics on top of video–even when tracking and recognizing objects like cards and markers. The AR SDK gives the position and orientation of the tracked object to a 3D engine which then renders geometry on top of the video frame coming from the device’s camera.

A 3D scan of myself overlaid on an AR card with Vuforia.

A 3D scan of myself overlaid on an AR card with Vuforia.

New technologies like Google’s Tango Tablet use Kinect-style depth cameras to store not only the color of each pixel, but the depth and position, too. (Well, sort of–the depth camera’s resolution is much lower than that of the color camera). This means that you can build a 3D model out of what the tablet’s camera sees as you move around an environment.

Tango displaying point cloud data of what it currently sees.

Tango displaying point cloud data of what it currently sees.

This feature has huge ramifications. Tango uses this data to do what is called “localization.” This means once an area is scanned, the tablet can compare the internal 3D model of the current environment it has stored with what the camera is currently seeing. When fused with compass and gyro data, the Tango tablet can compute its precise location inside the scanned area. This doesn’t take long either. Tango starts building the model immediately. Walk back to where you started using the tablet, and Tango knows where it is.

Usually this 3D data is stored as a point cloud. This is basically a 3D point for every position the 3D camera records.  Hence, a sufficiently complicated area will look like a cloud of dots–a point cloud. You can see an example of the Tango building a point cloud with the Room Scanner Tango app.

These point clouds are important for not only localization, but AR graphical effects such as occluding rendered 3D objects with the real world.  This is because a 3D mesh can be built out of these points which can be used for occlusion, collision and other features. Having objects in between you and the augmentation occlude the 3D render is essential to nailing the feeling that an AR object is really there.

Point clouds are awesome, but building them can be frustrating. Current point cloud scanners are bulky and slow, not to mention their accuracy issues can lead to jitter and other artifacts. Also, some depth cameras run at a frame rate low enough to make it hard to create point clouds without moving very slowly through an environment. Who wants to play a game where you have to walk around and meticulously scan a room before you can start?

In order for AR games and apps to succeed, devices need to effortlessly be able to sense and detect the 3D geometry of their surroundings. Yet, quick and instant generation of point clouds is far beyond the capabilities of current mobile sensor technology.

That’s where the public point cloud comes in.

A truly great Augmented Reality platform needs to upload point clouds generated by devices to the cloud.  Then, when a user uses some hot new wearable AR glasses, it can pull down a pre-made point cloud for the current location off of a server and use that until the glasses can update it from its own sensors. The device will then upload a fresh point cloud which can be used to refine the version stored online.

You can kind of see this already–Google and Apple Maps’ 3D satellite mode use similar point cloud reconstruction techniques presumably from aerial photos and other sources. Whereas these 3D models often look like something you’d see on the original PlayStation, the public point cloud will have to be much more detailed.  As sensors on mobile devices become more advanced, the crowdsourced point cloud data will become incredibly detailed.

Apple Maps' 3D reconstruction kind of looks like an original PlayStation game. The public point cloud will have to be higher resolution.

This 3D reconstruction kind of looks like an original PlayStation game. The public point cloud will have to be higher resolution. Oh, this is also where you can bet the best pastrami sandwich on the planet.

A massive, publicly accessible point cloud is not just necessary for the next generation of AR wearable devices. But also for self driving cars, drone navigation, and robotics (which is indeed where many of these algorithms came from in the first place). Privacy implications do exist, but perhaps not more so than Google Maps’ street view, or other current technologies that give you very precise information about your location.

In the near future, almost every public place on the planet will be stored in the cloud as 3D reconstructed geometry–passively built up and constantly refined by sensors embedded on countless mobile and wearable devices, perhaps without the user even knowing.

Adult Contemporary Video Games

One of my favorite Combat Jack podcasts of 2014 is when they interviewed legendary hip hop producer, Marley Marl over the Summer.  Marly Marl invented the modern hip-hop sound most take for granted and created the Juice Crew, one of the most important groups of MCs ever.

The Juice Crew

Before producing hit records, Marley had a career as an on-air DJ, starting on Mr. Magic‘s show on KISS-FM in New York.  In the ’90s he went on to host “Future Flavas” with Pete Rock on Hot 97.  Marley Marl was also still producing hit albums for the likes of LL Cool J and Lords of the Underground.

Times change, and Marley Marl isn’t producing music for 20 year olds anymore.  While many DJs desperately hang on to their fading youth, Marley tried another tactic.  He moved over to WBLS which plays old school hip hop for a mature audience.

it just so happens, rap fans in their fourties and beyond have far more disposable income than those in their teens and twenties.  His WBLS show has gone on to be a great success.  It turns out that despite being a youth-powered movement, there’s plenty of advertising dollars in hip-hop appealing to older rap fans.

This got me thinking about video games.

A lot of veteran developers are debating about the decline of AAA games in the face of the disruptive waves of free2play and mobile.  Many gamers in their demographic agree.  If that’s the case, why not appeal to this older audience?

The challenge to monetizing these gamers is that although they have the same taste in games they may have had over a decade ago, their play styles are vastly different due to lifestyle changes.  If you’ve got kids or a demanding job, perhaps you no longer have 120+ hours to spend playing an RPG. However, you might digest the same style of game in shorter episodic bursts on a tablet or smartphone.

Some developers have caught on to this and produce what I call Adult Contemporary Video Games.  A good example is the 1980s pencil and paper RPG, Shadowrun.  Microsoft’s attempt at AAA shooter based on Shadowrun was an abject failure (although I quite liked it).  Five years later, Harebrained Schemes went from a surge of support on Kickstarter for “Shadowrun Returns” to a series of popular mobile and PC downloadable games based on the franchise.

Shadowrun for iPad

This is a smart strategy–delivering content aimed at an older audience on newer devices.  Those of us who grew up not on just the original RPG, but the SNES and Genesis games were ripe for a new entry in the series.  This model has also seen success with Wasteland 2, and surely the upcoming Bard’s Tale sequel will continue the trend.

It remains to be seen if you can develop a new IP targeted at this audience.  A lot of what you hear on Adult Contemporary radio is old artists making new music.  In games it may be the same. So far, the genre seems to bank on nostalgia by resurrecting classic franchises for an older audience on new devices with updated play styles. Especially if you include teh current wave of retro remakes. While some veteran developers excel at creating games for the new mobile f2p masses, others may be more suited for this viable slice of the market.

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?

POSITIONAL TRACKING

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.

OCCLUDING VIRTUAL CHARACTERS WITH THE REAL WORLD

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.

ENVIRONMENTAL LIGHTING

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.

A QUICK TEST

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.

THERMAL ISSUES

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.

GRAPHICAL DETAIL

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.

CPU OPTIMIZATIONS

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.

IN CONCLUSION

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.