Avegant Glyph Review

Two years ago I made a post about a device called Avegant Glyph. I ended up investing in the Kickstarter. The estimated delivery during the Kickstarter campaign was December 2014. I finally got the Glyph two days ago.

It is a very cool device, but fell short of my expectations. Initially I spent a lot of time trying to get the position of the display calibrated for my eyes. It was very difficult to calibrate - I couldn't get a clear view of the entire rectangular display. The nose pieces that came with the device keep the display too far from my eyes. I found that removing the nose piece helps me get closer to the display, getting a clearer picture. However, I still can't get a completely clear view of the corners of the display even with my eyelashes touching the lens. The device is also a bit uncomfortable without a nose piece.

Ignoring the calibration issues, the quality of the display is amazing. Colors are very pure and reading text is easy. The display quality looks much better than the Oculus Rift developer versions. However, the resolution of the display is not very high.

Originally I was hoping this could be used as a complete replacement for my desktop monitor. The calibration issues really prevent this from working well. It is annoying to not be able to see text in the corner of the display clearly with both eyes. I tried watching a movie with the device while lying down. This worked well. The weight of the device was supported by the bed, so it was not uncomfortable. The corner calibration issues were hardly noticeable while watching the movie (probably because focusing on the edges wasn't necessary).

Raspberry Pi Thermostat Instructions

Here are some details on how I put together my Raspberry Pi thermostat.



My apartment's thermostat uses a very simple mechanism to control the heater:



Connecting the red wire to the white wire turns on the heater. Near the center of the thermostat is a glass vial containing some mercury. If the vial tilts to the right the mercury creates a connection between the wires. I attached the two black wires on the bottom and use the Raspberry Pi to control the connection between the wires. The original thermostat remains fully functional: the heater will turn on if either the Raspberry Pi or the original thermostat signal it to turn on.



Materials used:

• Raspberry Pi 2 Model B
• USB Wifi
• Pi Cobbler Plus
• Power supply
• SD card
• Songle SRD-05VDC-SL-C Relay
• Breadboard
• Wires

The relay module controls the connection between the two heater wires. GPIO output from the Raspberry Pi can turn the connection on/off. The connection is off by default - even when the Raspberry Pi is powered off. I SSH into the Raspberry Pi to control the GPIO pin over the Internet.

Raspberry Pi Thermostat

I connected a Raspberry Pi up to the heater in my apartment. Now I can control the heater over the Internet.

Update: more details posted here.

An Update on Baka

[previous post]

Although Baka Analytics has stopped updating, Baka is still alive. The occasional gaps in the data were due to Baka chewing through the wire which connects the magnetic sensor to the Raspberry Pi (which I had to fix several times). The outage since September 12 is a more serious issue: all of the USB ports on the Raspberry Pi stopped working. I think Baka caused this by urinating on the Raspberry Pi (which was stored next to his cage). I have ordered a replacement Raspberry Pi to use on another project, so it is unlikely I will restart Baka Analytics.

Baka's record was running 17.31 kilometers in a single night. In total Baka was recorded running 682.29 kilometers.

Metaball Go

Today I worked on a small HTML5 project: http://www.byronknoll.com/go.html

This is the board game Go rendered using metaballs.

Battle Map Explorer

Unfortunately the Kickstarter project I created did not get funded. Here is what the funding graph looked like: Today I released an open source project based on the idea used in the Kickstarter project: https://github.com/byronknoll/battle-map-explorer

cmix v8

I have released a new version of cmix. I have also migrated the code from a private Bitbucket repository to a public GitHub repository: https://github.com/byronknoll/cmix.

Kickstarter Project

I just launched my first Kickstarter project! https://www.kickstarter.com/projects/411355421/battle-map-explorer

Baka Analytics

I have a pet hamster named Baka. Baka spends most of his free time running on a hamster wheel. I put together a device to track the hamster wheel's rotation. It uses a Raspberry Pi 2, a magnetic sensor, and Google Analytics. Here is a webpage with live coverage of Baka's running: https://sites.google.com/site/bakaanalytics/. He tends to run about 6 kilometers per day (13,000 rotations) and sticks to a strict schedule of running between 10pm and 6am.

Picavet

I have been attempting to do aerial photography with a GoPro. My first attempt was using a quadcopter (Parrot AR.Drone):



Unfortunately the GoPro was too heavy for the quadcopter and it kept crashing. I tried two types of mounts for the camera: one on top (pictured above) and one suspended underneath the quadcopter using string. Mounting on top was more stable, but the quadcopter still occasionally crashed so it was too risky to attempt flying high altitudes.

One of my coworkers told me about a way to mount a camera to a kite using a device called a Picavet. I constructed my own Picavet using two wooden rulers and some carabiners:



It works great!

cmix v7

I just released cmix v7. I spent a long time fixing a bug which caused cmix v6 to crash in Windows. For v7 I focused on improving image compression.

Geometric Median

During a meeting with some coworkers we started debating if it was possible to find a better meeting location. Given the starting location of all the meeting participants, could we find a point which minimizes the total travel distance?

It turns out that it is not trivial to solve. The average of the participant locations is not necessarily the optimal point. The actual optimal point is called the geometric median.

I made a HTML5 page which visualizes the geometric median, along with the convex cost function: http://www.byronknoll.com/median.html

Cardboard

I finally own a VR device: Google Cardboard. It works surprisingly well! I am using it with a Nexus 5, which has a nice display. Cardboard doesn't work quite as well as the first developer edition of the Oculus Rift (see my review here), but it is pretty close. The demo apps for Cardboard are currently quite limited, so there isn't really much to do on it after the first 10 minutes. I am still waiting for my kickstarter edition of the Avegant Glyph: they have delayed the delivery date until next year :(

Wargames

I recently started a fun activity called wargaming. Wargames are a set of computer science related challenges/puzzles. So far I have completed three of the wargames on overthewire.org: Bandit, Krypton, and Leviathan. I track my progress on wechall.net. wechall.net tracks scores across dozens of wargaming sites and has user rankings/leaderboards. The wargames I have seen touch many different areas of computer science: cryptography, network security, linux tools, C++ debugging, etc. Very educational.

Dwarf Fortress

I recently beat GTA V, so I was looking for a new game to play. GTA V is the most expensive video game ever made and has amazing production value. I eventually decided on Slaves to Armok: God of Blood Chapter II: Dwarf Fortress as the next game I would try. It is on the opposite-end of the game spectrum compared to GTA V: it is free, made by a single developer, and has a text-based interface. I am a fan of NetHack and it looked like DF might have some similarities.

I have been playing DF for three days and so far it is incredible. The first day was tough since there is such a steep learning curve. My first fortress was a mess because I didn't understand how stairs/slopes worked - all my dwarves got trapped underground in a pit. I ended up watching a youtube tutorial to figure out the basics. After the tutorial I started up a second fortress and for the last two days I have managed to survive in this.

I had one near disaster when my fortress ran out of food. My dwarves were so hungry that they started ignoring my orders so I couldn't get them to work on actually finding new food sources. Some of my dwarves started dying and one went crazy and started attacking everyone. I thought I was doomed until suddenly a group of immigrants arrived. I immediately put the healthy immigrants to work on making/collecting food. Success!

Today I worked on creating a reliable water source for my fortress. I looked up how wells work on the DF wiki and starting building one. It ended up taking me two hours to finish the well. My fortress is underground and the most convenient water source was from a river on the surface. Channeling water around is dangerous because it could end up flooding my fortress or drowning the workers mining the tunnels. I built a tunnel from the river to a reservoir below my fortress. The well is connected to the reservoir. To control the flow of water I created two floodgates and connected them to levers in my fortress. I could then use the levers to control the flow of water from a safe distance, once the dwarves had finished digging and evacuating the reservoir. In the screenshot above you can see one level of my fortress and a party my dwarves organized in celebration of the new well.

visibility_polygon.js Version 1.5

I have released a new version of my visibility polygon library. One of the constraints in the old version was that none of the input line segments could intersect. In this new version, I added a function which breaks apart any intersecting line segments into non-intersecting components.

Demo: http://www.byronknoll.com/visibility.html

cmix v3

I have released cmix version 3. This version is over twice as fast, uses less memory, and gets better compression ratio.

Backpropagation

Today I derived backpropagation for a logistic activation function and a cross entropy loss function. This has been done before, but I couldn't find the full set of formulas for it online. I am using the variable notation from here: http://neuralnetworksanddeeplearning.com/chap2.html

cmix version 2

I have released cmix version 2. It is now first place on the Large Text Compression Benchmark.

cmix version 1

I have released cmix version 1. It is now ranked first place on the Silesia Benchmark and second place on the Large Text Compression Benchmark.