Why does everything in my VR headset look so pixelated? It’s supposed to be using a 2160×1200 screen, but my 1080p desktop monitor looks so much sharper!
This is yet another fundamental question about VR that pops up over and over again, and like the others I have addressed previously, it leads to interesting deeper observations. So, why do current-generation head-mounted displays appear so low-resolution?
Here’s the short answer: In VR headsets, the screen is blown up to cover a much larger area of the user’s field of vision than in desktop settings. What counts is not the total number of pixels, and especially not the display’s resolution in pixels per inch, but the resolution of the projected virtual image in pixels per degree, as measured from the viewer’s eyes. A 20″ desktop screen, when viewed from a typical distance of 30″, covers 37° of the viewer’s field of vision, diagonally. The screen (or screens) inside a modern VR headset cover a much larger area. For example, I measured the per-eye field of view of the HTC Vive as around 110°x113° under ideal conditions, or around 130° diagonally (it’s complicated), or three and a half times as much as that of the 20″ desktop monitor. Because a smaller number of pixels (1080×1200 per eye) is spread out over a much larger area, each pixel appears much bigger to the viewer.
Now that Vrui is working on the HTC Vive (at least until the next SteamVR update breaks ABI again), I can finally go back and give Vrui-based applications some tender loving care. First up is 3D Visualizer, an application to visualize and, more importantly, visually analyze three-dimensional volumetric data sets (see Figure 1).
Figure 1: Analyzing a CAT scan with 3D Visualizer on the HTC Vive. Cat included.
I found out today that HTC now ships a tool to measure users’ inter-pupillary distances with new Vive VR headsets. When I say “tool,” I mean a booklet with instructions in many languages, and a ruler printed along one edge of each page:
Figure 1: IPD measurement chart shipped by HTC with new Vives. Image courtesy of reddit user DanielDC88, image source.
I thought this was great on multiple levels. For one, measuring the user’s IPD and entering it into the VR software, either manually or through a sensor on a physical IPD adjustment knob or slider on the headset, as in both Vive and Oculus Rift, is an important component of creating convincing VR displays. The more people get used to that, the better.
On the second level, I was proud. On April 9, 2014, I wrote an article on this here blog titled “How to Measure Your IPD,” which describes this exact method of using a mirror and a ruler. It even became one of my more popular articles (the fifth most popular article, actually, with 33,952 views as of today). I was a little less proud when I looked at my own article again just now, and realized that my diagrams were absolutely hideous compared to those in HTC’s booklet. Oh well. Continue reading →
It has been way too long that I have publicly released a new version of the Vrui VR toolkit. The main issue was that I had been chasing evolving hardware, from the Oculus Rift DK1 to the Oculus Rift DK2, and now to HTC’s Vive. During that long stretch of time, I was never happy with the state of support of any of these devices.
That’s finally changed. I have been working on full native support for HTC’s Vive head-mounted display over the last few months (with the first major break-through in May), and I think it’s working really well. There are still a lot of improvements to make and sharp edges to sand off, but I feel it is worthwhile releasing the software as it is now to get some early testing done. So without much further ado, here is Vrui-4.2-004.
Figure 1: Vrui’s ClusterJello toy application running on an HTC Vive head-mounted display. Recorded using a second-generation Microsoft Kinect camera (Kinect-for-Xbox-One). Continue reading →
To my surprise and delight, I recently found out that Valve has been releasing Linux versions of most of their SteamVR/OpenVR run-time/SDK for a while now (OpenVR just hit version 1.0.0, go get it while it’s fresh). This is great news: it will allow me to port Vrui and all Vrui applications to the Vive headset and its tracked controllers in one fell swoop.
But before diving into developing a Lighthouse tracking driver plug-in for Vrui’s input device abstraction layer, I decided to cobble together a small testing utility to get a feel for OpenVR’s internal driver interface, and for the Lighthouse tracking system’s overall tracking quality.
Figure 1: The Lighthouse 6-DOF tracking system, disassembled (source).
With the first commercial version of the Oculus Rift (Rift CV1) now trickling out of warehouses, and Rift DK2, HTC Vive DK1, and Vive Pre already being in developers’ hands, it’s time for a more detailed comparison between these head-mounted displays (HMDs). In this article, I will look at these HMDs’ lenses and optics in the most objective way I can, using a calibrated fish-eye camera (see Figures 1, 2, and 3).
Figure 1: Picture from a fisheye camera, showing a checkerboard calibration target displayed on a 30″ LCD monitor.
Figure 2: Same picture as Figure 1, after rectification. The purple lines were drawn into the picture by hand to show the picture’s linearity after rectification.
Figure 3: Rectified picture from Figure 2, re-projected into stereographic projection to simplify measuring angles. Concentric purple circles indicate 5-degree increments away from the projection center point.
Last Friday I made a trek down to the San Francisco peninsula, to visit and chat with a couple of other VR folks: Cyberith, SVVR, and AltspaceVR. In the process, I also had the chance to try a couple of VR devices I hadn’t seen before.
Virtual locomotion, and its nasty side effect, simulator sickness, are a pretty persistent problem and timely topic with the arrival of consumer VR just around the corner. Many enthusiasts want to use VR to explore large virtual worlds, as in taking a stroll through the frozen tundra of Skyrim or the irradiated wasteland of Fallout, but as it turns out, that’s one of the hardest things to do right in VR.
Figure 1: Cyberith Virtualizer, driven by an experienced user (Tuncay Cakmak). Yes, you can jump and run, with some practice.