Head mounted display or HMD
This is probably one of the most common terms you're bound to run into in hearing or reading about virtual reality, especially because for the most part, HMDs are the current form of hardware delivering VR experiences to users. It's typically goggles or a helmet of some type, the kind you strap to your face or put on your head. That's where you're viewing the VR experience. Some have sensors for head tracking, some don't.
Speaking of head tracking, this term refers to the sensors that keep up with the movement of the user's head and move the images being displayed so that they match the position of the head. In short, if you're wearing an Oculus Rift, for example, head tracking is what lets you look to the left, right, up, or down, and see the world that's been built in those directions.
Eyetracking is similar to headtracking, but instead reads the position of the users' eyes versus their head. So for example, there's an HMD (you learned this earlier!) called FOVE that integrates eye tracking into their headset. In their demo, the user can aim a weapon (it looks like a laser) by looking in a different direction. Alternatively, a game like Rocket Toss relies on the user aiming with his or her head to determine the direction of rings.
Field of view (FOV)
Field of view is the angle of degrees in a visual field. Having a higher field of view is important because it contributes to the user having a feeling of immersion in a VR experience. The viewing angle for a healthy human eye is about 200 degrees. So, the bigger that angle is, the more immersive it feels.
If you've ever tried a VR experience and noticed that when you turn your head, the visuals don't quite keep up, that's latency. It's unpleasant, because that's not something that happens in the real world. That lag is an oft-cited complaint about VR experiences that aren't up to par for a variety of reasons.
Simulator sickness is a conflict of sorts between what your brain and body think they're doing. Your eyes say, "We're moving!" And your brain says "Nope! Let's get nauseated!" Science Magazine suggests that this disparity is interpreted as a toxin, and the human body does what it can to get that toxin out, ergo, vomiting. As much as people look at virtual reality and want to do things like fly or jump, for many folks, it's the beginning of a bad idea. But, as everyone has different thresholds, not everyone gets sick, or as sick as someone else might. This is one of the big challenges for developers — figuring out how to move people without making them ill.
Outside of virtual reality, judder is a significant shaking. But as for VR, Oculus' CTO Michael Abrash defined it like this in a blog post from 2013 when he was still at Valve Software: "a combination of smearing and strobing that's especially pronounced on VR/AR HMDs."
If you're looking at a television, or, in this case, a virtual reality experience, you're looking at a series of images. The refresh rate is how fast those images get updated. Higher refresh rates cut down on lag, and cutting down on lag means there's less of a chance of getting sick. It also means more responsive experiences. You definitely want to be north of 60 frames per second.
Here's another word that's not exclusive to virtual reality, but still gets play. It's tactile feedback. In VR, that would mean users feeling like they're touching something that's not really there. In June, Oculus unveiled its Oculus Touch controllers — the Half Moon prototype, and one of the features was haptics.
If virtual reality strives to takes users and immerse them in new environments, presence is what's achieved when that happens. Plain and simple, users feel like they're there, wherever "there" is.
There's not exactly a definitive definition. It's a bit prickly. Broadly, it's a bit of a philosophical underpinning of virtual reality; Forbes defines it as a "collective virtual reality," but there's plenty of debate about what that applies to and really, what exactly that is. A suggestion: check out Snowcrash by Neal Stephenson. It's a 1992 sci-fi that envisions a metaverse.
This term refers to a type of app that aims to create a shared VR space where users can interact with each other and even participate in activities.
For the most part, there are two types of VR you'll run into. There's the kind that's computer-generated graphics, and the kind made of real images. The latter is cinematic VR, and is made using cameras, whether rigs made of mounted GoPros or actual 360 cameras.
There is a difference between virtual reality and 360-degree video. The latter is less immersive and typically keeps the viewer in a fixed point surrounded by roughly 360 degrees of video. This is what you're most likely to see if you're playing around with YouTube 360 or Google Cardboard apps. Purists will say that 360 video is not actually virtual reality.
Stitching is the process of taking footage from different cameras, like GoPro cameras that have been used in a 360 camera mount, and combining that footage into spherical video. The process usually involves reorienting video, placing seams, and generally editing it so that it looks like one continuous view, rather than a patchwork of angles.
The slightly embarrassing, slack-jawed look people get on their face when they wear an HMD.
Oculus started off as a Kickstarter project. Facebook bought the company in 2014 for $2 billion. In the past several years, Oculus released two developer kits and demoed different prototypes. The consumer version of the Rift will start shipping in the spring of 2016. The Rift is considered high-end VR and requires a fairly souped up PC in order to run. Later in the year, Oculus will release its natively-built hand controllers, called Touch. Until then, units will ship with Xbox One wireless controllers.
The buzz has been that the Vive might be the Rift's best competition. The Vive is a partnership between hardware maker HTC, and video game maker Valve, powered by the SteamVR platform. It has two wireless hand controllers, and three sensors called lighthouses, to be placed in the room. What's cool about the Vive is that it provides a full room experience. Users can stand up and move around a set space as they interact with their games and apps. The Vive also requires a powerful PC to run. The Vive will start shipping in April 2016.
Sony's PlayStation VR
Formerly Project Morpheus, PlayStation VR will be compatible with PlayStation 4. PSVR is the only console-based VR system so far. It works with the DualShock PlayStation controllers, but users can also purchase handheld Move controllers. Movement is more limited than with the Vive. PSVR is considered the third of the trio of high-end VR systems (the other two being he Oculus and Vive). It's less immersive than the Oculus or the Vive, but it is cheaper, and has the advantage of a 36-million unit install base of PlayStation 4s already out in the wild. PSVR will ship in November 2016.
Samsung Gear VR
The Gear is powered by Oculus, but differs in that its display is the screen of the Samsung Galaxy phones, as well as the Note 5. There have been three iterations. The newest is compatible with the Samsung Galaxy 7. The Samsung platform features a variety of games, game demos, 360 photos, 360 videos, and other VR experiences, both computer-generated and cinematic.
Google introduced its cardboard holder in 2014 at its I/O conference. A user's smartphone fits into the front, and the user holds the unit up to his or her face. It does not contain sensors, which makes some VR purists dismiss it as too low quality, as it relies on the phone's accelerometer. On the other hand, the two facts that it's cheap and the newer version accommodates phones with screens up to 6 inches can potentially put VR in the hands of a very wide audience. There's also the Cardboard app. Users can find apps on the Google Play store. Cardboard units (as well as its knockoffs) can be customized and branded with company logos, meaning that they're being used as marketing tools. Google is reportedly working on a new headset that is made of plastic and has a few sensors.