Last week at GDC, Norm and I got to try out Valve's SteamVR demo. The technology Valve (along with their hardware partner HTC) demoed simultaneously at the Game Developer Conference in San Francisco and Mobile World Congress in Barcelona is nothing short of revolutionary. That's not hyperbole; with one 18-minute demo, Valve one-upped every other company that's making virtual reality hardware. It wasn’t with an ultra-high resolution display, either--it was with perfect positional tracking.

For the last year or two, Valve's virtual reality demo has been a thing that people discussed in hushed tones in the hallway outside conference sessions and after meetings. "I haven't seen it yet, but so-and-so has and it was amazing" usually followed by disclaimers like "I may have felt presence, but it was still just a prototype."

What we saw at GDC was still "just a prototype," but it's a prototype without the rough edges we've become accustomed to. Positional tracking was fast and glitch free for both the headset and the unconventional controllers. In fact, both the scale and placement of the controllers in the VR environment was good enough that I was able to reach out and grab them with goggles on. The controllers in the virtual environment were perfectly mapped to the location of the physical controllers in the real world. I saw them in the virtual world and was able to grab them in the physical world. This is amazing.

Valve did all this with display hardware that is, on paper at least, nothing special compared to the latest prototypes from Sony and Oculus. The HTC Vive has the same field of view that Oculus's Crescent Bay prototypes we've tried, and it lacks the 120Hz refresh rate we saw on Sony’s latest Project Morpheus prototype. My 18 minutes in the SteamVR room changed how I thought about VR hardware--specs like field of view and display persistence matter far less for VR than the system’s ability to perfectly match your movement in the physical and virtual world.

The only thing that matters is whether you feel presence.

Presence is a notoriously difficult phenomenon to describe. Usually people make a half-hearted attempt at a description, then follow up by saying you just have to experience it for yourself. Presence happens when virtual reality gear tricks the deep reptilian parts of your brain with a convincing enough simulation of reality that your brain treats the virtual space as if you are actually inhabiting it, on both a conscious and subconscious level. That means if you stand on the edge of a cliff and look down, you get vertigo. If an obstacle is in your path, you subconsciously move to avoid it. When an object flies at your face, you respond to it reflexively, dodging or blocking because of impulses that originate from your spine, not your conscious brain. When your brain loses track of the fact that you're just looking at a virtual environment and begins to treat it as real, the result is intoxicating.

Unfortunately though, to really understand presence you do have to experience it for yourself.

If you want to do that, you will need a high-resolution, low-latency display paired with a low-latency motion-tracking mechanism, positional audio, a fast computer, some sort of controller that makes sense inside the virtual reality metaphor, and the software to make it all work together seamlessly. That is all difficult. But the only metric that really matters is binary: Is the hardware good enough to trick your brain? While I've experienced fleeting moments of presence in demos from Oculus and Sony, what Valve showed us at GDC is that they've solved for presence. Moments after the demo started, I lost all track of my real-world surroundings and got lost in the virtual. That feeling of presence sustained for all 18 minutes of that demo.

As is often the case, getting the hardware right is just the beginning. Traditional video games have stolen the language of cinema, but that won’t work for VR. Today, games can take control of the camera to make sure the player focuses on the action without issue. However, that same action--moving the camera independent of the players input breaks presence at best or makes the player sick in the worst case. Instead of taking control of the camera, VR game developers have to invent new cues to direct the player's attention. Even relatively simple storytelling tasks, such as transitioning between scenes, require thought and iterative testing. If VR excels at 1:1 movement inside a 15-foot square, how does the player’s avatar traverse a two-mile maze that doesn’t fit inside those boundaries? If wipes and fades don't make sense inside the context of VR, how do you indicate the passage of time or a flashback sequence? Developers building games for virtual reality need to reinvent the building blocks of visual storytelling that have evolved over the last 100 years in order to take advantage of the new medium.

This week was a huge leap forward for virtual reality. Valve showed us VR hardware and software that went beyond the simple experiences and short vignettes we've seen in the past. They showed us a tool for artists, a cooking simulator, and a game scene that showed multiple ways to tell stories in VR. They demonstrated presence in virtual reality.

Ironically, Valve gave developers a ship date for the first wave of VR games. Yes, the HTC Vive will be available by the end of this year. There will be games. Normal people will be able to experience virtual reality and presence at home. Virtual reality is indeed real, and it will be here in time for Christmas.