I started regretting uploading my “Embedding 2D Desktops into VR” video, and the post describing it, pretty much right after I did it, because there was such an obvious thing to do, and I didn’t think of it.
There has been a lot of discussion about VR movies in the blogosphere and forosphere (just to pick two random examples), and even on Wired, recently, with the tenor being that VR movies will be the killer application for VR. There are even downloadable prototypes and start-up companies.
But will VR movies actually ever work?
This is a tricky question, and we have to be precise. So let’s first define some terms.
When talking about “VR movies,” people are generally referring to live-action movies, i.e., the kind that is captured with physical cameras and shows real people (well, actors, anyway) and environments. But for the sake of this discussion, live-action and pre-rendered computer-generated movies are identical.
We’ll also have to define what we mean by “work.” There are several things that people might expect from “VR movies,” but not everybody might expect the same things. The first big component, probably expected by all, is panoramic view, meaning that a VR movie does not only show a small section of the viewer’s field of view, but the entire sphere surrounding the viewer — primarily so that viewers wearing a head-mounted display can freely look around. Most people refer to this as “360° movies,” but since we’re all thinking 3D now instead of 2D, let’s use the proper 3D term and call them “4π sr movies” (sr: steradian), or “full solid angle movies” if that’s easier.
The second component, at least as important, is “3D,” which is of course a very fuzzy term itself. What “normal” people mean by 3D is that there is some depth to the movie, in other words, that different objects in the movie appear at different distances from the viewer, just like in reality. And here is where expectations will vary widely. Today’s “3D” movies (let’s call them “stereo movies” to be precise) treat depth as an independent dimension from width and height, due to the realities of stereo filming and projection. To present filmed objects at true depth and with undistorted proportions, every single viewer would have to have the same interpupillary distance, all movie screens would have to be the exact same size, and all viewers would have to sit in the same position relative the the screen. This previous post and video talks in great detail about what happens when that’s not the case (it is about head-mounted displays, but the principle and effects are the same). As a result, most viewers today would probably not complain about the depth in a VR movie being off and objects being distorted, but — and it’s a big but — as VR becomes mainstream, and more people experience proper VR, where objects are at 1:1 scale and undistorted, expectations will rise. Let me posit that in the long term, audiences will not accept VR movies with distorted depth.
Now this is why I run a blog. In my video and post on the Oculus Rift’s internals, I talked about distortions in 3D perception when the programmed-in camera positions for the left and right stereo views don’t match the current left and right pupil positions, and how a “perfect” HMD would therefore need a built-in eye tracker. That’s still correct, but it turns out that I could have done a much better job approximating proper 3D rendering when there is no eye tracking.
This improvement was pointed out by a commenter on the previous post. TiagoTiago asked if it wouldn’t be better if the virtual camera were located at the centers of the viewer’s eyeballs instead of at the pupils, because then light rays entering the eye straight on would be represented correctly, independently of eye vergence angle. Spoiler alert: he was right. But I was skeptical at first, because, after all, that’s just plain wrong. All light rays entering the eye converge at the pupil, and therefore that’s the only correct position for the virtual camera.
Well, that’s true, but if the current pupil position is unknown due to lack of eye tracking, then the only correct thing turns into just another approximation, and who’s to say which approximation is better. My hunch was that the distortion effects from having the camera in the center of the eyeballs would be worse, but given that projection in an HMD involving a lens is counter-intuitive, I still had to test it. Fortunately, adding an interactive foveating mechanism to my lens simulation application was simple.
Turns out that I was wrong, and that in the presence of a collimating lens, i.e., a lens that is positioned such that the HMD display screen is in the lens’ focal plane, distortion from placing the camera in the center of the eyeball is significantly less pronounced than in my approach. Just don’t ask me to explain it for now — it’s due to the “special properties of the collimated light.” 🙂
I have to make a confession: I’ve been playing with the Oculus Rift HMD for almost a year now, and have been supporting it in Vrui for a long time as well, but I haven’t really spent much time using it in earnest. I’m keenly aware of the importance of calibrating head-mounted displays, of course, and noticed right away that the scale of virtual objects seen through the Rift was way off for me, but I never got around to doing anything about it. Until now, that is.
Update: Please tear your eyes away from the blue lady and also read this follow-up post. It turns out things are worse than I thought. Now back to your regularly scheduled entertainment.
I somehow missed this when it was hot a few weeks or so ago, but I just found out about an interesting Kickstarter project: HOLOVISION — A Life Size Hologram. Don’t bother clicking the link, the project page has been taken down following a DMCA complaint and might not ever be up again.
Why do I think it’s worth talking about? Because, while there is an actual design for something called Holovision, and that design is theoretically feasible, and possibly even practical, the public’s impression of the product advertised on Kickstarter is decidedly not. The concept imagery associated with the Kickstarter project presents this feasible technology in a way that (intentionally?) taps into people’s misconceptions about holograms (and I’m talking about the “real” kind of holograms, those involving lasers and mirrors and beam splitters). In other words, it might not be a scam per se, and it might even be unintentional, but it is definitely creating a false impression that might lead to very disappointed backers.
I was just reminded of an article in The New Yorker that I read a long time ago, in June 2006. The article, written by eminent neurologist Oliver Sacks, describes the experience of an adult woman, Susan R. Barry, a professor of neurobiology herself, who had been stereoblind her entire life, and suddenly regained stereoscopic vision after intensive visual training at the age of 48. While the full original article, titled “Stereo Sue,” is behind the New Yorker’s pay wall, I just found an awesome YouTube video of a joint interview with Drs. Barry and Sacks:
I wrote about my first impressions of the Oculus Rift developer kit back in April, and since then I’ve been working (on and off) on getting it fully and natively supported in Vrui (see Figure 1 for proof that it works). Given that Vrui’s somewhat insane flexibility is a major point of pride for me, what was it that I actually had to create to support the Rift? Turns out, not all that much: a driver for the Rift’s built-in inertial tracking unit and a post-processing filter to correct for the Rift’s lens distortion were all it took (more on that later). So why did it take me this long? For one, I was mostly working on other things and only spent a few hours here and there, but more importantly, the Rift is not just a new head-mounted display (HMD), but a major shift in how HMDs are (or will be) used.
I went to zCon 2013, the zSpace developers conference, held in the Computer History Museum in Mountain View yesterday and today. As I mentioned in my previous post about the zSpace holographic display, my interest in it is as an alternative to our current line of low-cost holographic displays, which require assembly and careful calibration by the end user before they can be used. The zSpace, on the other hand, is completely plug&play: its optical trackers (more on them below) are integrated into the display screen itself, so they can be calibrated at the factory and work out-of-the-box.
So I drove around the bay to get a close look at the zSpace, to determine its viability for my purpose. Bottom line, it will work (with some issues, more on that below). My primary concerns were threefold: head tracking precision and latency, stylus tracking precision and latency, and stereo quality (i.e., amount of crosstalk between the eyes).
My friend Serban got his Oculus Rift dev kit in the mail today, and he called me over to check it out. I will hold back a thorough evaluation until I get the Rift supported natively in my own VR software, so that I can run a direct head-to-head comparison with my other HMDs, and also my screen-based holographic display systems (the head-tracked 3D TVs, and of course the CAVE), using the same applications. Specifically, I will use the Quake ||| Arena viewer to test the level of “presence” provided by the Rift; as I mentioned in my previous post, there are some very specific physiological effects brought out by that old chestnut, and my other HMDs are severely lacking in that department, and I hope that the Rift will push it close to the level of the CAVE. But here are some early impressions.
So it appears the Oculus Rift is really happening. A buddy of mine went in early on the kickstarter, and his will supposedly be in the mail some time this week. In a way the Oculus Rift, or, more precisely, the most recent foray of VR into the mainstream that it embodies, was the reason why I started this blog in the first place. I’m very much looking forward to it (more on that below), but I’m also somewhat worried that the huge level of pre-release excitement in the gaming world might turn into a backlash against VR in general. So I made a video laying out my opinions (see Figure 1, or the embedded video below).