Beyond Pokémon GO: The Secret to a Better Augmented Reality Experience

Software that can analyze tiny motions in video allows real objects to be dynamically simulated in augmented reality

3 min read
Pokemon Go creature frolics in bushes
Gif: Abe Davis/IEEE Spectrum

imgWith interactive dynamic video, Pokémon characters can be made to appear to interact with the real world instead of merely overlaying it.Gif: Abe Davis/IEEE Spectrum

Whether or not you understand the recent drive to fill the world around you with obnoxious animated characters that you can only see as long as you hold your phone up in front of your face at all times, augmented reality does have the potential to enhance our world in ways that are occasionally useful. However, the AR experience is currently a sterile one, with augmentations overlaid on top of, but not really a part of, the underlying reality.

Abe Davis is a graduate student at MIT who we've written about before in the context of using a candy wrapper and a camera as a microphone. You should absolutely click here for a more intimate introduction to Abe Davis, but if you're not a fan of incredibly nerdy rap music, we'll just move on to Abe's thesis dissertation, which describes interactive dynamic video (IDV). Rather than using 3D graphics to model the motion characteristics of objects, IDV extracts motion information from a small amount of 2D video, and then generates simulations of objects in that video, allowing the augmented part of AR to interact directly with the reality part, turning static objects into objects that you (or your virtual characters) can play with.

To understand how this works, imagine a simple moving object, like bedsheet hanging on a clothesline in a gentle breeze. As the wind blows, the sheet will ripple, and those ripples will consist of a horizontal component (movement across the sheet) as well as a vertical component (movement up or down the sheet). Once you've figured out these motion components, called resonant or vibration modes, you can simulate them individually or combine them together in ways that can mimic a breeze blowing in a different direction or at a different strength. The fundamental knowledge that you gain about how the real sheet moves on a very basic level allows you (and a real-time video editor) to make the sheet in the video move in a realistic way as well, without being constrained by reality itself.

This method can be applied to much more complicated objects than bedsheets, although it gets trickier to pick out all of the vibration modes. For it to work properly, you need a stable, baseline video of the scene, you need to move the object that you're interested in simulating, and you need to watch it move for long enough that you can accurately extract the vibration modes that you care about, which may take a minute or two. Unfortunately, this means that using it for Pokemon GO is probably not realistic unless you have a lot more patience and restraint than the typical Pokemon GO player seems to have, because you can't just wander around and point your phone at physical objects that can be instantly animated (yet):

As curmudgeonly as we are about whatever silly games kids (and some adults) are playing these days, the underlying technology here is very cool, and there's potential for many different applications. Generally, modeling a real world object for any purpose, from civil engineering analysis to making animated movies, requires first making a detailed 3D model of that object and applying a physics engine to get it to move. With interactive dynamic video, you can skip the complicated and time-consuming 3D modeling step to create a virtual model with reality-based physics. Such a model may not offer the same movement space as a full 3D model, but that's a reasonable trade-off for only having to spend a minute or two with video camera and a tripod to create it. 

While Davis has no immediate plans to commercialize any of this (he's heading to Stanford for his postdoc in the fall), MIT has a patent on the technique, and it's not difficult for Davis to speculate about where we might see IDV in the near future.

“[W]hen you look at VR companies like Oculus, they are often simulating virtual objects in real spaces," he says. "This sort of work turns that on its head, allowing us to see how far we can go in terms of capturing and manipulating real objects in virtual space.”

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The Inner Beauty of Basic Electronics

Open Circuits showcases the surprising complexity of passive components

5 min read
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A photo of a high-stability film resistor with the letters "MIS" in yellow.
All photos by Eric Schlaepfer & Windell H. Oskay
Blue

Eric Schlaepfer was trying to fix a broken piece of test equipment when he came across the cause of the problem—a troubled tantalum capacitor. The component had somehow shorted out, and he wanted to know why. So he polished it down for a look inside. He never found the source of the short, but he and his collaborator, Windell H. Oskay, discovered something even better: a breathtaking hidden world inside electronics. What followed were hours and hours of polishing, cleaning, and photography that resulted in Open Circuits: The Inner Beauty of Electronic Components (No Starch Press, 2022), an excerpt of which follows. As the authors write, everything about these components is deliberately designed to meet specific technical needs, but that design leads to “accidental beauty: the emergent aesthetics of things you were never expected to see.”

From a book that spans the wide world of electronics, what we at IEEE Spectrum found surprisingly compelling were the insides of things we don’t spend much time thinking about, passive components. Transistors, LEDs, and other semiconductors may be where the action is, but the simple physics of resistors, capacitors, and inductors have their own sort of splendor.

High-Stability Film Resistor

A photo of a high-stability film resistor with the letters "MIS" in yellow.

All photos by Eric Schlaepfer & Windell H. Oskay

This high-stability film resistor, about 4 millimeters in diameter, is made in much the same way as its inexpensive carbon-film cousin, but with exacting precision. A ceramic rod is coated with a fine layer of resistive film (thin metal, metal oxide, or carbon) and then a perfectly uniform helical groove is machined into the film.

Instead of coating the resistor with an epoxy, it’s hermetically sealed in a lustrous little glass envelope. This makes the resistor more robust, ideal for specialized cases such as precision reference instrumentation, where long-term stability of the resistor is critical. The glass envelope provides better isolation against moisture and other environmental changes than standard coatings like epoxy.

15-Turn Trimmer Potentiometer

A photo of a blue chip
A photo of a blue chip on a circuit board.

It takes 15 rotations of an adjustment screw to move a 15-turn trimmer potentiometer from one end of its resistive range to the other. Circuits that need to be adjusted with fine resolution control use this type of trimmer pot instead of the single-turn variety.

The resistive element in this trimmer is a strip of cermet—a composite of ceramic and metal—silk-screened on a white ceramic substrate. Screen-printed metal links each end of the strip to the connecting wires. It’s a flattened, linear version of the horseshoe-shaped resistive element in single-turn trimmers.

Turning the adjustment screw moves a plastic slider along a track. The wiper is a spring finger, a spring-loaded metal contact, attached to the slider. It makes contact between a metal strip and the selected point on the strip of resistive film.

Ceramic Disc Capacitor

A cutaway of a Ceramic Disc Capacitor
A photo of a Ceramic Disc Capacitor

Capacitors are fundamental electronic components that store energy in the form of static electricity. They’re used in countless ways, including for bulk energy storage, to smooth out electronic signals, and as computer memory cells. The simplest capacitor consists of two parallel metal plates with a gap between them, but capacitors can take many forms so long as there are two conductive surfaces, called electrodes, separated by an insulator.

A ceramic disc capacitor is a low-cost capacitor that is frequently found in appliances and toys. Its insulator is a ceramic disc, and its two parallel plates are extremely thin metal coatings that are evaporated or sputtered onto the disc’s outer surfaces. Connecting wires are attached using solder, and the whole assembly is dipped into a porous coating material that dries hard and protects the capacitor from damage.

Film Capacitor

An image of a cut away of a capacitor
A photo of a green capacitor.

Film capacitors are frequently found in high-quality audio equipment, such as headphone amplifiers, record players, graphic equalizers, and radio tuners. Their key feature is that the dielectric material is a plastic film, such as polyester or polypropylene.

The metal electrodes of this film capacitor are vacuum-deposited on the surfaces of long strips of plastic film. After the leads are attached, the films are rolled up and dipped into an epoxy that binds the assembly together. Then the completed assembly is dipped in a tough outer coating and marked with its value.

Other types of film capacitors are made by stacking flat layers of metallized plastic film, rather than rolling up layers of film.

Dipped Tantalum Capacitor

A photo of a cutaway of a Dipped Tantalum Capacitor

At the core of this capacitor is a porous pellet of tantalum metal. The pellet is made from tantalum powder and sintered, or compressed at a high temperature, into a dense, spongelike solid.

Just like a kitchen sponge, the resulting pellet has a high surface area per unit volume. The pellet is then anodized, creating an insulating oxide layer with an equally high surface area. This process packs a lot of capacitance into a compact device, using spongelike geometry rather than the stacked or rolled layers that most other capacitors use.

The device’s positive terminal, or anode, is connected directly to the tantalum metal. The negative terminal, or cathode, is formed by a thin layer of conductive manganese dioxide coating the pellet.

Axial Inductor

An image of a cutaway of a Axial Inductor
A photo of a collection of cut wires

Inductors are fundamental electronic components that store energy in the form of a magnetic field. They’re used, for example, in some types of power supplies to convert between voltages by alternately storing and releasing energy. This energy-efficient design helps maximize the battery life of cellphones and other portable electronics.

Inductors typically consist of a coil of insulated wire wrapped around a core of magnetic material like iron or ferrite, a ceramic filled with iron oxide. Current flowing around the core produces a magnetic field that acts as a sort of flywheel for current, smoothing out changes in the current as it flows through the inductor.

This axial inductor has a number of turns of varnished copper wire wrapped around a ferrite form and soldered to copper leads on its two ends. It has several layers of protection: a clear varnish over the windings, a light-green coating around the solder joints, and a striking green outer coating to protect the whole component and provide a surface for the colorful stripes that indicate its inductance value.

Power Supply Transformer

A photo of a collection of cut wires
A photo of a yellow element on a circuit board.

This transformer has multiple sets of windings and is used in a power supply to create multiple output AC voltages from a single AC input such as a wall outlet.

The small wires nearer the center are “high impedance” turns of magnet wire. These windings carry a higher voltage but a lower current. They’re protected by several layers of tape, a copper-foil electrostatic shield, and more tape.

The outer “low impedance” windings are made with thicker insulated wire and fewer turns. They handle a lower voltage but a higher current.

All of the windings are wrapped around a black plastic bobbin. Two pieces of ferrite ceramic are bonded together to form the magnetic core at the heart of the transformer.

This article appears in the February 2023 print issue.

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