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.
Figure 1: Screenshot from video showing VR ProtoShop run simultaneously in a 3D environment created by an Oculus Rift and a Razer Hydra, and in a 2D environment using mouse and keyboard, brought into the 3D environment via the VNC remote desktop protocol.
There have been several discussions on the Oculus subreddit recently about how to integrate 2D desktops or 2D applications with 3D VR environments; for example, how to check your Facebook status while playing a game in the Oculus Rift without having to take off the headset.
This is just one aspect of the larger issue of integrating 2D and 3D applications, and it reminded me that it was about time to revive the old VR VNC client that Ed Puckett, an external contractor, had developed for the CAVE a long time ago. There have been several important changes in Vrui since the VNC client was written, especially in how Vrui handles text input, which means that a completely rewritten client could use the new Vrui APIs instead of having to implement everything ad-hoc.
Here is a video showing the new VNC client in action, embedded into LiDAR Viewer and displayed in a desktop VR environment using an Oculus Rift HMD, mouse and keyboard, and a Razer Hydra 6-DOF input device:
In a previous post, I looked at the Oculus Rift’s internal projection in detail, and did some analysis of how stereo rendering setup is explained in the Rift SDK’s documentation. Looking at that again, I noticed something strange.
In the other post, I simplified the Rift’s projection matrix as presented in the SDK documentation to
which, to those in the know, doesn’t look like a regular OpenGL projection matrix, such as created by glFrustum(…). More precisely, the third row of P is off. The third-column entry should be 
What’s the difference? It’s subtle. Changing the third row of the projection matrix doesn’t change where pixels end up on the screen (that’s the good news). It only changes the z, or depth, value assigned to those pixels. In a standard OpenGL frustum matrix, 3D points on the near plane get a depth value of 1.0, and those on the far plane get a depth value of -1.0. The 3D clipping operation that’s applied to any triangle after projection uses those depth values to cut off geometry outside the view frustum, and the viewport projection after that will map the [-1.0, 1.0] depth range to [0, 1] for z-buffer hidden surface removal.
Using a projection matrix as presented in the previous post, or in the SDK documentation, will still assign a depth value of -1.0 to points on the far plane, but a depth value of 0.0 to points on the (nominal) near plane. Meaning that the near plane distance given as parameter to the matrix is not the actual near plane distance used by clipping and z buffering, which might lead to some geometry appearing in the view that shouldn’t, and a loss of resolution in the z buffer because only half the value range is used.
I’m assuming that this is just a typo in the Oculus SDK documentation, and that the library code does the right thing (I haven’t looked).
Oh, right, so the fixed projection matrix, for those working along, is
A cluster of earthquakes always gets the news media interested in geology, at least for a short time, and Monday’s 4.4 in southern California, following last week’s series of north coast quakes up to 6.9, was no different. Our local media’s go-to guy for earthquakes and other natural hazards is Dr. Gerald Bawden of the USGS Sacramento. Gerald also happens to be one of the main users of the KeckCAVES visualization facility and KeckCAVES software, and so he took an interview with our local Fox-affiliate in the CAVE, “to get out of the wind,” as he put it.
Here’s the video. Caution: ads after the jump.
Oculus recently presented the “Crystal Cove,” a version of the Rift head-mounted display with built-in optical tracking, which is combined with the existing inertial tracker to provide a full 6-DOF (position and orientation) tracking solution at low latency, and it is rumored that the Crystal Cove will be released as development kit mark 2 after this year’s Game Developers Conference.
This is great news. I’ve been saying for a long time that Oculus cannot afford to drop positional head tracking on developers at the last minute, because it will break several assumptions built into game engines and other VR software (but let’s talk about game engines here). I’m also happy because the Crystal Cove uses precisely the tracking technology that I predicted: active markers (LEDs) on the headset, and an external camera placed at a fixed position in the environment. I am also sad because I didn’t manage to finish my own after-market optical tracking add-on before Oculus demonstrated their new integrated technology, but that’s life.
So why does positional head tracking break existing games? Because for the first time, the virtual camera used to render a game world is no longer under sufficient control of the software. Let’s take a step back. In a standard, desktop, 3D game, the camera is entirely controlled by the software. The software sets it to some position and orientation determined by the game logic, the 3D engine renders the virtual world for that camera setup, and the result is the displayed image.
Serial entrepreneur Elon Musk posted this double whammy of cryptic messages to his Twitter account on August 23rd:
@elonmusk: We figured out how to design rocket parts just w hand movements through the air (seriously). Now need a high frame rate holograph generator.
@elonmusk: Will post video next week of designing a rocket part with hand gestures & then immediately printing it in titanium
As there are no further details, and the video is now slightly delayed (per Twitter as of September 2nd: @elonmusk: Video was done last week, but needs more work. Aiming to publish link in 3 to 4 days.), it’s time to speculate! I was hoping to have seen the video by now, but oh well. Deadline is deadline.
First of all: what’s he talking about? My best guess is a free-hand, direct-manipulation, 6-DOF user interface for a 3D computer-aided design (CAD) program. In other words, something roughly like this (just take away the hand-held devices and substitute NURBS surfaces and rocket parts for atoms and molecules, but leave the interaction method and everything else the same):
In my detailed how-to guide on installing and configuring Vrui for Oculus Rift and Razer Hydra, I did not talk about installing any actual applications (because I hadn’t released Vrui-3.0-compatible packages yet). Those are out now, so here we go.
If you happen to own a Kinect for Xbox (Kinect for Windows won’t work), you might want to install the Kinect 3D Video package early on. It can capture 3D (holographic, not stereoscopic) video from one or more Kinects, and either play it back as freely-manipulable virtual holograms, or it can, after calibration, produce in-system overlays of the real world (or both). If you already have Vrui up and running, installation is trivial.
As promised, here is a detailed guide to get Vrui version 3 running with an Oculus Rift (and optionally a Razer Hydra, since that seems to be the 6-DOF input device du jour).
If you are already running Linux, good for you. Skip the next paragraph.
If you don’t have Linux yet, go and grab it. I personally prefer Fedora, but it’s generally agreed[citation needed] that Ubuntu is the easiest to install for new Linux users, so let’s go with that. The Ubuntu installer makes it quite easy to install alongside an existing Windows OS on your system. Don’t bother installing Linux inside a virtual machine, though: that way Vrui won’t get access to your high-powered graphics cards, and performance will be abysmal. It won’t be able to talk to your Rift, either.
One of the first things to do after a fresh Linux install is to install the vendor-supplied drivers for your graphics card (if you don’t have a discrete Nvidia or ATI/AMD graphics card, go buy a GeForce!). Installing binary drivers is much easier these days. Here are instructions for Nvidia and ATI/AMD cards. If you happen to be on Fedora, enable the rpmfusion repositories and get the appropriate driver packages from there.
I just released version 3.0 of the Vrui VR toolkit. One of the major new features is native support for the Oculus Rift head-mounted display, including its low-latency inertial 3-DOF (orientation-only) tracker, and post-rendering lens distortion correction. So I thought it’s time for the first (really?) Vrui post in this venue.
Glad you’re asking. In a nutshell, Vrui (pronounced to start with vroom, and rhyme with gooey) is a high-level toolkit to develop highly interactive applications aimed at holographic (or fully-immersive, or VR, or whatever you want to call them) display environments. A large selection of videos showing many Vrui applications running in a wide variety of environments can be found on my YouTube channel. To you as a developer, this means you write your application once, and users can run it in any kind of environment without you having to worry about it. If new input or output hardware comes along, it’s Vrui’s responsibility to support it, not yours.
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.
Figure 1: The trademark “double-barrel” Oculus Rift screenshot, this time generated by a Vrui application.
