Ceci n’est pas une pipe bombe


This is the picture of the homemade clock Ahmed Mohamed brought to his Irving, Texas high school. Apparently no one ever mistook it for a bomb, but they did suspect that it was made to look like a bomb and so they dragged the hapless boy off in handcuffs and suspended him for three days.

This is a strange case of perception versus reality in which the virtual bomb was never mistaken for a real bomb. Instead, what was identified was the fact that it was, in fact, only a bomb virtually and, as with all things virtual, therefore required some sort of explanation.

The common sympathetic explanation is that this isn’t a picture of a virtual bomb at all but rather a picture of a homemade clock. Ahmed recounts that he made the clock, in maker fashion, in order to show an engineering teacher because he had done robotics in middle school and wanted to get into a similar program in high school. Homemade clocks, of course, don’t require an explanation since they aren’t virtually anything other than themselves.


It turns out, however, that the picture at the top does not show a homemade maker clock. Various engineering types have examined the images and determined that it is in fact a disassembled clock from the 80’s.

The telling aspect is the DC power cord which doesn’t actually get used in homemade projects. Instead, anyone working with arduino projects typically (pretty much always) uses AA batteries. The clock components have also been tracked back to their original source, however, so the evidence seems pretty solid.


The photo at the top shows not a virtual bomb nor a homemade clock but, in fact, a virtual homemade clock. That is, it was made to look like a homemade clock but was mistakenly believed to be something made to look like a homemade bomb.

[As a disclaimer about intentions, which is necessary because getting on the wrong side of this gets people in trouble, I don’t know Ahmed’s intentions and while I’m a fan of free speech I can’t say I actually believe in free speech having worked in marketing and I think Ahmed Mohammed looks absolutely adorable in his NASA t-shirt and I have no desire to be placed in company with those other assholes who have shown that this is not a real homemade clock but rather a reassembled 80’s clock and therefore question Ahmed’s motives whereas I refuse to try to get into a high schooler’s head, having two of my own and knowing what a scary place that can be … something, something, something … and while I can’t wholeheartedly support every tweet made by Richard Dawkins and have at times even felt in mild disagreement with things he and others have tweeted on twitter I will say that I find his book The Selfish Gene a really good read … etc, etc, … and for good measure fuck you FoxNews.]



The salient thing for me is that we all implicitly know that a real bomb isn’t supposed to look like a bomb. The authorities at Ahmed’s high school knew that immediately. Bombs are supposed to look like shoes or harmless tourist knickknacks. If you think it looks like a bomb, it obviously isn’t. So what does it mean to look like a bomb (to be virtually a bomb) but not be an actual bomb?


I covered similar territory once before in a virtual exhibit called les fruits dangereux and at the time concluded that virtual objects, like post-modern novels, involve bricolage and the combining of disparate elements in unexpected ways. For instance combining phones, electrical tape and fruit or combining clock parts and pencil cases. Disrupting categorical thinking at a very basic level makes people – especially authority people – suspicious and unhappy.

Which gets us back to racism which is apparently what has happened to Ahmed Mohammed who was led out of school in handcuffs in front of his peers – and we’re talking high school! and he wasn’t asking to be called “McLovin.” It’s pretty cruel stuff. The fear of racial mixing (socially or biologically) always raises it’s head and comes from the same desire to categorize people and things into bento box compartments. The great fear is that we start to acknowledge that we live in a continuum of types rather than distinct categories of people, races and objects. In the modern age, mass production makes all consumer objects uniform in a way that artisanal objects never were while census forms do the same for people.

Virtual reality will start by copying real world objects in a safe way. As with digital design, it will start with isomorphism to make people feel safe and comfortable. As people become comfortable, bricolage will take hold simply because, in a digital world rather than a commoditized/commodified world, mashups are easy. Irony and a bit of subversiveness will lead to bricolage with purpose as we find people’s fantasies lead them to combine digital elements in new and unexpected ways.

We can all predict augmented and virtual ways to press a digital button or flick through a digital menu projected in front of us in order to get a virtual weather forecast. Those are the sorts of experiences that just make people bored with augmented reality vision statements.


The true promise of virtual reality and augmented reality is that they will break down our racial, social and commodity thinking. Mixed-reality has the potential to drastically change our social reality. How do social experiences change when the color of a person’s avatar tells you nothing real about them, when our social affordances no longer provide clues or shortcuts to understanding other people? In a virtual world, accents and the shoes people wear no longer tell us anything about their educational background or social status. Instead of a hierarchical system of discrete social values, we’ll live in a digital continuum.

That’s the sort of augmented reality future I’m looking forward to.

The important point in the Ahmed Mohammed case, of course, is that you shouldn’t arrest a teenager for not making a bomb.

The Problem with Comparing Depth Camera Resolutions

We all want to have an easy way to compare different depth cameras to one another. Where we often stumble in comparing depth cameras, however, is in making the mistake of thinking of them in the same way we think of color cameras or color displays.

When we go to buy a color television or computer monitor, for instance, we look to the pixel density in order to determine the best value. A display that supports 1920 by 1080 has roughly 2.5 times the pixel density of a 1280 by 720 display. The first is considered high definition resolution while the second is commonly thought of as standard definition. From this, we have a rule of thumb that HD is 2.5 times denser than SD. With digital cameras, we similarly look to pixel density in order to compare value. A 4 megapixel camera is roughly twice as good as a 2 megapixel camera, while an 8 MP camera is four times as good. There are always other factors involved, but for quick evaluations the pixel density trick seems to work. My phone happens to have a 41 MP camera and I don’t know what to do with all those extra megapixels – all I know is that it is over 20 times as good as that 2 megapixel camera I used to have and that makes me happy.

When Microsoft’s Kinect 2 sensor came out, it was tempting to compare it against the Kinect v1 in a similar way: by using pixel density. The Kinect v1 depth camera had a resolution of 320 by 240 depth pixels. The Kinect 2 depth camera, on the other hand, had an increased resolution of 512 b 424 depth pixels. Comparing the total depth pixels provided by the Kinect v1 to the total provided by the Kinect 2: 76,800 vs 2, 217,088, many people arrived at the conclusion that the Kinect 2’s depth cameras was roughly three times better than the Kinect v1’s.

Another feature of the Kinect 2 is a greater field of view for the depth camera. Where the Kinect v1 has a field of view of 57 degrees by 43 degrees, the Kinect 2 has a 70 by 60 degree field of view. The new Intel RealSense 3D F200 camera, in turn, advertises an improved depth resolution of 480 by 360 degrees with an increased field of view of roughly 90 degrees by 72 degrees.

What often gets lost in these feature comparisons is that our two different depth camera attributes, resolution and field of view, can actually affect each other. Increased pixel resolution is only really meaningful if the field of view stays the same between different cameras. If we increase the field of view, however, we are in effect diluting the resolution of each pixel by trying to stuff more of the real world into the pixels we already have.

It turns out that 3D math works slightly differently from regular 2D math. To understand this better, imagine a sheet of cardboard held a meter out in front of each of our two Kinect sensors. How much of each sheet is actually caught by the Kinect v1 and the Kinect 2?


To derive the area of the inner rectangle captured by the Kinect v1 in the diagram above, we will use a bit of trigonometry. The field of view of the Kinect v1 is 58.5 degrees horizontal by 46.6 vertical. To get good angles to work with, however, we will need to bisect these angles. For instance, half of 46.6 is 23.3. The tangent of 21.5 degrees times the 1 meter hypotenuse (since the cardboard sheet is 1 M away) gives us an opposite side of .39 meters. Since this is only half of that rectangle’s side (because we bisected the angle) we multiply by two to get the full vertical side which is .78 meters. Using the same technique for the horizontal field of view, we capture a horizontal side of 1.09 meters.

Using the same method for the sheet of cardboard in front of the Kinect 2, we discover that the Kinect 2 captures a rectangular surface that is 1.4 meters by 1.14 meters. If we now calculate the area on the cardboard sheets in front of each camera and divide by each camera’s resolution, we discover that far from being three times better than the Kinect v1, each pixel caught by the Kinect 2 depth camera holds 1.5 times as much of the real world as each pixel of the Kinect v1. It is still a better camera, but not what one would think by comparing resolutions alone.

This was actually a lot of math in order to make a simple and mundane point: it all depends. Depth pixel resolutions do not tell us everything we need to know when comparing different depth cameras. I invite the reader to compare the true density of the RealSense 3D camera to the Kinect 2 or Xtion Pro Live camera if she would like.

On the other hand, it might be worth considering the range of these different cameras. The RealSense F200 cuts off at about a meter whereas the Kinect cameras only start performing really well at about that distance. Another factor is, of course, the accuracy of the depth information each camera provides. A third factor is whether one can improve the performance of a camera by throwing on more hardware. Because the Kinect 2 is GPU bound, it will actually work better if you simply add a better graphics card.

For me, personally, the most important question will always be how good the SDK is and how strong the community around the device is. With good language and community support, even a low quality depth camera can be made to do amazing things. An extremely high resolution depth camera with a weak SDK, alternatively, might in turn make a better paperweight than a feature forward technology solution.

[I’d like to express my gratitude to Kinect for Windows MVPs Matteo Valoriani and Vincent Guigui for introducing me to this geometric bagatelle.]

HoloLens Fashionista


While Google Glass certainly had its problems as an augmented reality device – among other things not really being an augmented reality device as GA Tech professor Blair MacIntyre pointed out – it did demonstrate two remarkable things. First, that people are willing to shell out $1500 for new technology. In the debates over the next year concerning the correct price point for VR and AR head mounted displays, this number will play a large role. Second, it demonstrated the importance of a sense of style when designing technology. Google glass, for many reasons, was a brilliant fashion accessory.

If a lesson can be drawn from these two data points, it might be that new — even Project Glass-level iffy — technology can charge a lot if it manages to be fashionable as well as functional.

When you look at the actual HoloLens device, you may, like me, be thinking “I don’t know if I’d wear that out in public.” In that regard, I’d like to nudge your intuitions a bit.

Obviously there is time to do some tweaking with the HL design. I recently found some nostalgic pictures online that made me start to think that with modifications, I could rock this look.

It all revolves around one of the first animes imported to the United States in the 70s called Battle of the Planets. It sounded like this:

Battle of the Planets! G-Force! Princess! Tiny! Keyop! Mark! Jason! And watching over them from Center Neptune, their computerized coordinator, 7-Zark-7! Watching, warning against surprise attacks by alien galaxies beyond space. G-Force! Fearless young orphans, protecting Earth’s entire galaxy. Always five, acting as one. Dedicated! Inseparable! Invincible!


And it looked AMAZING. I think this look could work for HoloLens. I think I could pull it off. The capes and tights, of course, are purely optional.







Microsoft Windows 10







Why Augmented Reality is harder than Virtual Reality


At first blush, it seems like augmented reality should be easier than virtual reality. Whereas virtual reality involves the generation of full stereoscopic digital environments as well as interactive objects to place in those environments, augmented reality is simply adding digital content to our view of the real world. Virtual reality would seem to be doing more heavy lifting.


In actual fact, both technologies are creating illusions to fool the human eye and the human brain. In this effort, virtual reality has an easier task because it can shut out points of reference that would otherwise belie the illusion. Augmented reality experiences, by contrast, must contend with real world visual cues that draw attention to the false nature of the mixed reality content being added to a user’s field of view.

In this post, I will cover some of the additional challenges that make augmented reality much more difficult to get right. In the process, I hope to also provide clues as to why augmented reality HMDs like HoloLens and Magic Leap are taking much longer to bring to market than AR devices like the Oculus Rift, HTC Vive and Sony Project Morpheus.

terminator vision

But first, it is necessary to distinguish between two different kinds of augmented reality experience. One is informatics based and is supported by most smart phones with cameras. The ideal example of this type of AR is the Terminator-vision from James Cameron’s 1984 film “The Terminator.” It is relatively easy to to do and is the most common kind of AR people encounter today.

star wars chess

The second, and more interesting, kind of AR requires inserting illusory 3D digital objects (rather than informatics) into the world. The battle chess game from 1977’s “Star Wars” epitomizes this second category of augmented reality experience. This is extremely difficult to do.

The Microsoft HoloLens and Magic Leap (as well as any possible HMDs Apple and others might be working on) are attempts to bring both the easy type and the hard type of AR experience to consumers.

Here are a few things that make this difficult to get right. We’ll put aside stereoscopy which has already been solved effectively in all the VR devices we will see coming out in early 2016.

cloaked predator

1. Occlusion The human brain is constantly picking up clues from the world in order to determine the relative positions of objects such as shading, relative size and perspective. Occlusion is one that is somewhat tricky to solve. Occlusion is an effect that is so obvious that it’s hard to realize it is a visual cue. When one body is in our line of sight and is positioned in front of another body, that other body is partially hidden from our view.

In the case where a real world object is in front of a digital object, we can clip the digital object with an outline of the object in front to prevent bleed through. When we try to create the illusion that a digital object is positioned in front of a real world object, however, we encounter a problem inherent to AR.

In a typical AR HMD we see the real world through a transparent screen upon which digital content is either projected or, alternatively, illuminated as with LED displays. An obvious characteristic of this is that digital objects on a transparent display are themselves semi-transparent. Getting around this issue would seem to require being able to make certain portions of the transparent display more opaque than others as needed in order to make sure our AR objects look substantial and not ghostly.

 citizen kane

2. Accommodation It turns out that stereoscopy is not the only way our eyes recognize distance. The image above is from a scene in Orson Welles’s “Citizen Kane” in which a technique called “deep focus” is used extensively. Deep focus maintains clarity in the frame whether the actors and props are in the foreground, background or middle ground. Nothing is out of focus. The technique is startling both because it is counter to the way movies are generally shot but also because it is counter to how our eyes work.

If you cover one eye and use the other to look at one of your fingers, then move the finger toward and away from you, you should notice yourself refocusing on the finger as it moves while other objects around the finger become blurry. The shape of the cornea actually becomes more rounded when objects are close in order to cause light to refract more in order to reach the retina. For further away objects, the cornea flattens out because less refraction is needed. As we become older, the ability to bow the cornea lessens and we lose some of our ability to focus on near objects – for instance when we read. In AR, we are attempting to make a digital object that is really only centimeters from our eyes appear to be much further away.

Depending on how the light from the display passes through the eye, we may end up with the digital object appearing clear while the real world objects supposedly next to it and at the same distance appear blurred.


3. Vergence-Accommodation Mismatch The accommodation problem is one aspect of yet another VR/AR difficulty. The term vergence describes the convergence and divergence of the two eyes from one another as objects move closer or further away. An interesting aspect of stereoscopy – which is used both for virtual reality as well as augmented reality to create the illusion of depth – is that the distance at which the two eyes coordinate to see an object is generally different from the focal distance from the eyes to the display screen(s). This consequently sends two mismatched signals to the brain concerning how far away the digital object is supposed to be. Is it the focal length or the vergence length? Among other causes, vergence-accommodation mismatch is believed to be a contributing factor to VR sickness. Should the accommodation problem above be resolved for a given AR device, it is safe to assume that the vergence-accommodation mismatch will also be solved.

 4. Tetherless Battery Life Smart phones have changed our lives among other reasons because they are tetherless devices. While the current slate of VR devices all leverage powerful computers to which they are attached, since VR experiences are all currently somewhat stationary (the HTC Vive being the odd bird), AR needs to be portable. This naturally puts a strain on the battery, which needs to be relatively light since it will be attached to the head-mounted-display, but also long-lived as it will be powering occasionally intensive graphics, especially for games.

5. Tetherless GPU Another strain on the system is the capability of the GPU. Virtual reality devices can be fairly intense since they require the user to purchase a reasonably powerful and somewhat expensive graphics card. AR devices can be expected to have similar graphics requirements as VR with much less to work with since the GPU needs to be onboard. We can probably expect a streamlined graphics pipeline dedicated to and optimized for AR experiences will help offset lower GPU capabilities.

6. Applications Not even talking about killer apps, here. Just apps. Microsoft has released videos of several impressive demos including Minecraft for HoloLens. Magic Leap up to this point has only shown post-prod, heavily produced illustrative videos. The truth is that everyone is still trying to get their heads around designing for AR. There aren’t really any guidelines for how to do it or even what interactions will work. Other than the most trivial experiences (e.g. weather and clock widgets projected on a wall) this will take a while as we develop best practices while also learning from our mistakes.


With the exception of V-AM, these are all problems that VR does not have to deal with. Is it any wonder, then, that while we are being led to believe that consumer models of the Oculus Rift, HTC Vive and Sony Project Morpheus will come to market in the first quarter of 2016, news about HoloLens and Magic Leap has been much more muted. There is simply much more to get right before a general rollout. One can hope, however, that dev units will start going out soon from the major AR players in order to mitigate challenge #6 while further tuning continues, if needed, on challenges #1-#5.

Come hear me speak about Mixed Reality at Dragon Con 2015


I’ve been invited by the Robotics and Maker Track to speak about near future technologies at Dragon Con this year. While the title of the talk is “Microsoft Kinect and HoloLens,” I’ll actually be talking more broadly about 3D sensors like Kinect and the Orbbec Astra, Virtual Reality with the Oculus Rift and HTC Vive as well as Augmented Reality with HoloLens and Magic Leap. I will cover how these technologies will shape our lives and potentially change our world over the next five years.

I am honored to have been asked to be a panelist at Dragon Con on technology I am passionate about and that has been a large part of my life and work over the past several years.

I should add that being a panelist at Dragon Con is a nerd and fan’s freakin’ dream come true for me. Insanely so. Hopefully I’ll be able to stay cool enough to get through all the material I have on our collective sci fi future.


I will cover each technology and the devices coming out in the areas of 3D sensors, virtual reality and augmented reality. I’ll discuss their potential impact as well as some of their history. I’ll delve into some of the underlying technical and commercial challenges that face each. I’ll bring lots of Kinect and Oculus demos (not allowed to show HoloLens for now, unfortunately) and will also provide practical advice on how to experience these technologies as a consumer as well as a developer in 2016.


My panel is on Sunday, Sept 6 at 2:30 in Savannah rooms 1, 2 and 3 in the Sheraton. Please come say hi!