The HTC Vive, Oculus Rift and PS VR will be no doubt top of your list in you're on the hunt for a virtual reality headset. But Intel has something even more interesting in the works.
Its Alloy headset is coming later this year and solves many of the issues with the first wave of modern VR headsets, by using a different approach.
It doesn't need cameras on tripods scattered around your living room, doesn't rely on a PC or games console and it's not an augmented reality set like the Microsoft HoloLens either. It's multiplayer VR that incorporates objects in your house or flat into each wearer's experience.
Alloy is based on what Intel calls "merged reality".
Defining merged reality
Merged reality "allows people to digitally capture, then seamlessly interact with and manipulate their physical and virtual interactions and objects in any way imagination allows," says Tim Parker, vice president of Intel's Perceptual Computing Group.
It's effectively VR plus AR, sometimes now known as mixed reality - though that term is used to describe varying degrees of blending virtual and physical environments.
"A good example of how merged reality would work in your lounge was demonstrated at CES where we showcased a living room set up that allows users to experience the untethered capabilities while their room was scanned and incorporated into a video game," says Parker.
This is the VR dream, and it hinges on five tenets, only a couple of which are covered by the virtual reality headsets currently on sale. It's about "being untethered, providing freedom of movement with six degrees of mobility, integrated tracking for a seamless inside-out experience, natural manipulation for more than sight and sounds, and integrated real-world content."
The "six degrees of mobility" part simply means tracking of movement across the X, Y and Z axes plus pitch, yaw and roll. In other words, full tracking of the player's movement in a 3D space.
Intel has also shown off a few different methods of interaction using the headset. In August 2016, the experience was led with your actual hands, letting you wave over objects to 'use' them.
At CES in January 2017 we saw an Intel Alloy controller, although it was an Ximmerse model designed to work with multiple headsets rather than one made just for Intel Alloy. You wouldn't catch HTC doing this, but Intel's project is a little different.
Intel has managed to level-up the VR experience using fewer pieces of hardware than the current crowd. "Project Alloy is an all-in-one device", says Parker. All the processing happens in the headset, with no other device required: no £1500 PC, no games console.
How? It's down to three important pieces of hardware, different from those seen in other headsets: Intel Core 7th generation processors, Intel RealSense cameras and tech by Movidius, a company acquired by Intel in September 2016.
Let's start with RealSense. Most depth-tracking camera rigs use a pair of camera sensors to determine depth in the way our eyes do, using the parallax effect to tell between close and far objects.
Instead of using two cameras, RealSense uses a single one plus an infrared transmitter and receiver. The transmitter projects an infrared signal onto your room, the IR reflects off walls and objects, and the time it takes to reach the receiver lets Alloy know how far away objects are. Xbox Kinect uses similar tech.
This is why the final version of Alloy will only need one camera, even though the current work-in-progress set has two.
Put Alloy on and start playing, your living room clutter becomes part of the terrain
"The current prototype uses two RealSense cameras, but we will evolve the device to use one. The production version camera will have a much higher field of view (FOV) in all directions that allows it to singularly create the depth maps that are currently created by two cameras in our prototype today," Parker tells us.
A quick look at the prototype currently being shown-off tells you why the current hardware uses two 'eyes'. The cameras are actually angled away from each other, used to cover a field of view somewhat comparable with what our eyes see, rather than sitting on a flat plane as the dual '3D' cameras in phones do.
In its current state, Intel Alloy scans the room before you even start 'playing'. It reportedly takes a minute or so, but this is where Movidius' technology comes in.
Now-Intel-owned Movidius designed a VPU, a vision processing unit, called the Myriad 2. It's an ultra-low energy piece of hardware that recognises and tracks objects in a scene in real time, able to tell not just the size and position of them but have a good crack at guessing what they are. With the right software any mobile processor could do this, but this one does so using just half a watt of power.
In theory at least, this could wipe out that initial scanning process, letting you simply put the Intel Alloy on and start playing. Your living room clutter becomes part of the virtual terrain. Intel hasn't said the Myriad 2 will simply be plugged-into the next version of the headset, but Parker did tell us "you will see that technology become integrated into the next iteration." It's exciting stuff.
The main processing brain of the Intel Alloy, though, is a 7th gen Intel Core CPU. We pressed Intel for more information on exactly what type of processor will be used, as that's an entire family of the things. It isn't telling, yet.
It doesn't take too much techy nous to make some sensible predictions, though. One of Intel's Y-series chipsets seems the most likely choice, for several reasons. These are used in super-slim laptops like the Acer Swift 7, because they consume very little power and can get by using just metal heatsinks rather than using noisy CPU-cooling fans. Any standard Core i3, i5 or i7 processor would almost certainly need fans because they create up to three times the heat.
Here's where we hit the one obvious snag of the Alloy.
Don't expect PS4 ports
Intel's processors have great productivity power but, particularly those of the Y-series, do not have super-powered graphics processors. You can see the effects of this in action in some of Intel's demos of the hardware.
Alloy can produce immersive 3D environments, but it is unrealistic to expect the sort of high-res textures and polygon counts you'd see from a HTC Vive or Oculus Rift hooked-up to a £1500 PC. This needn't kill your immersion, though. Some of the most involving VR experiences use fairly simply visuals, like Job Simulator, and getting rid of all the wires involved with current VR setups will be a huge benefit.
This streamlining of processor power means that an Intel Alloy headset can be powered by a battery that sits on the back of the headband, handily also balancing-out the weight of the front part.
What we see today, or even in the 'final' Intel Alloy headset, isn't the endgame.
Alloy won't end up being a single headset, but an open-source platform, with the software APIs and hardware specs available to headset makers (none of which have been announced yet). Of course, Intel is still going to benefit when the building blocks of the system use Intel gear.
More mixed reality picks
"There are many use cases possible with this technology," says Parker. Looking at the tech decisions Intel has made as a whole, it's still too early to see how Alloy will fit in alongside the existing devices and Microsoft's big Windows VR and HoloLens plans.
Whether Alloy ends up in our homes, in architects' offices or those of estate agents depends to an extent on which manufacturers end up signing up with Intel. Intel's own consumer Alloy headset is expected to start shipping out towards the end of 2017.