Kevin Reid's blog

As vaguely promised before, another update on what I've been working on for the past couple of years:

ShinySDR (why yes, I am terrible at naming things) is a software-defined radio receiver application.

Specifically, it is in the same space as Gqrx, SDR#, HDSDR, etc.: a program which runs on your computer (as opposed to embedded in a standalone radio) and uses a peripheral device (rtl-sdr, HackRF, USRP, etc.) for the RF interface. Given such a device, it can be used to listen to or otherwise decode a variety of radio transmissions (including the AM and FM broadcast bands everyone knows, but also shortwave, amateur radio, two-way radios, certain kinds of telemetry including aircraft positions, and more as I get around to it).

ShinySDR is basically my “I want my own one of these” project (the UI still shows signs of “I’ll just do what Gqrx did for now”), but it does have some unique features. I'll just quote myself from the README:

I (Kevin Reid) created ShinySDR out of dissatisfaction with the user interface of other SDR applications that were available to me. The overall goal is to make, not necessarily the most capable or efficient SDR application, but rather one which is, shall we say, not clunky.

Here’s some reasons for you to use ShinySDR:

• Remote operation via browser-based UI: The receiver can be listened to and remotely controlled over a LAN or the Internet, as well as from the same machine the actual hardware is connected to. Required network bandwidth: 3 Mb/s to 8 Mb/s, depending on settings.

  Phone/tablet compatible (though not pretty yet). Internet access is not required for local or LAN operation.

• Persistent waterfall display: You can zoom, pan, and retune without losing any of the displayed history, whereas many other programs will discard anything which is temporarily offscreen, or the whole thing if the window is resized. If you zoom in to get a look at one signal, you can zoom out again.

• Frequency database: Jump to favorite stations; catalog signals you hear; import published tables of band, channel, and station info; take notes. (Note: Saving changes to disk is not yet well-tested.)

• Map: Plot station locations from the frequency database, position data from APRS and ADS-B, and mark your own location on the map. (Caveat: No basemap, i.e. streets and borders, is currently present.)

Supported modes:

• Audio: AM, FM, WFM, SSB, CW.
• Other: APRS, Mode S/ADS-B, VOR.

If you’re a developer, here’s why you should consider working on ShinySDR (or: here’s why I wrote my own rather than contributing to another application):

• All server code is Python, and has no mandatory build or install step.

• Plugin system allows adding support for new modes (types of modulation) and hardware devices.

• Demodulators prototyped in GNU Radio Companion can be turned into plugins with very little additional code. Control UI can be automatically generated or customized and is based on a generic networking layer.

On the other hand, you may find that the shiny thing is lacking substance: if you’re looking for functional features, we do not have the most modes, the best filters, or the lowest CPU usage. Many features are half-implemented (though I try not to have things that blatantly don’t work). There’s probably lots of code that will make a real DSP expert cringe.

Now that I've finally written this introduction post, I hope to get around to further posts related to the project.

At the moment, I'm working on adding the ability to transmit (given appropriate hardware), and secondarily improving the frequency database subsystem (particularly to have a useful collection of built-in databases and allow you to pick which ones you want to see).

Side note: ShinySDR may hold the current record for most popular program I've written by myself; at least, it's got 106 stars on GitHub. (Speaking of which: ShinySDR doesn't have a page anywhere on my own web site. Need to fix that — probably starting with a general topics/radio. Eventually I hope to have a publicly accessible demo instance, but there’s a few things I want to do to make it more multiuser and robust first.)

My GLToyJS project now has a live instance so you can play with it without setting up your own server. Caveats: • I don't promise it will remain at this URL or that the parameter format won't change. • There is an automatic 5-minute-interval change to a new random effect which cannot be disabled (but you can undo it by going back). • It doesn't tell you if your browser doesn't have WebGL, it just stops (gray screen).

Some new features in Cubes:

• An automated test suite. It’s hardly complete coverage, but at least it exists and so can grow. (I ended up going with Jasmine for in-browser testing. I’m not a big fan of the Englishy syntax, but it does the job reasonably well and has niceties like rerunning individual tests and adequate support for asynchronous tests.)
• Precise collision against rotated blocks: you can now walk up the slope of those funky pyramid blocks, and so on. Stairs, anyone?
• Performance monitoring widget with fancy graphs. (If you click the “[-]” to hide it, then it won’t waste CPU time updating itself, either.)

[I was asked about Cubes “Where do you think you might take the game play next?” and it turned into this.]

My original motivation for creating Cubes was a combination of the “blocks out of blocks” idea — which itself came from immersion in the graphics of Minecraft — and also dissatisfaction with certain bugs, limitations, and design choices in Minecraft. As a result, I’m not just building a voxel game; I’m building a game that shares what I like about Minecraft.

(What I like about Minecraft, broadly, is survival and engineering — I like building structures and machines to make my virtual life easier.)

Now, creating a Minecraft clone would be unoriginal — not just compared to Minecraft but because Minecraft clones are an entire genre. But I don’t have experience with what little exists of a genre of voxel building games to synthesize my own thing, and I myself am looking for something like Minecraft. What can I do? Here’s what I’ve been trying:

• Be different.

  Whenever I see an opportunity to do something specifically unlike Minecraft, that doesn’t compromise what I’m trying to do, I take it and see what happens. However, most of these experiments have failed; for example, Cubes originally had a larger-scaled player character, but this turned out bad because it means tunneling and building is 8× more tedious, and it reduces the apparent size of the world. Also, it leads to thinking “OK, add this feature Minecraft has — but (superficially) differently!”

• Be generic.

  This is my long-term goal, and it is one that ties neatly into the “blocks made of blocks” theme. The characteristics of blocks can be defined by building circuits (programs) inside them. What I’m aiming for is that by creating a blockset (collection of block designs which the player can build with), one is defining the game that can be played, by giving those blocks specific behaviors.

  In this way, I am working towards having a game which can be programmed to emulate Minecraft.

  (I have a working prototype of an importer for Minecraft worlds as well as for Minecraft blocks — that is, turning the terrain.png from a Minecraft texture pack into Cubes' 3D blocks — but I am not going to release that code until and unless I determine that Mojang doesn’t mind my doing so. I still love Minecraft and they deserve my not stepping on their toes that far.)

  However, this means both that Cubes itself needs to be very generic, and that the built-in example uses of such features should feel different from Minecraft.

So, returning to the original topic of “where am I going next”, I need to add the following functionality to the game world:

• Extend the circuits feature so that there can be blocks that are active and interactive (e.g. opening and closing doors, “physics” like Minecraft falling sand and growing plants).

• Add moving objects (for vehicles and mobs). I intend to generalize these so that they are worlds in themselves — this will allow large or unique vehicles, and mean that they can be designed using the same game tools.

• Add some form of resource constraints/conservation laws (as in Minecraft survival mode) — that is, you have to gather stuff to make it into other stuff. I haven’t figured out specifically how I want to do this yet, and this seems particularly tricky to make programmable. One idea that keeps coming to mind is that when you break a block, specific subcubes are “resource cubes” (according to their type in the block world) which you collect, and in order to place a block you need to have the corresponding resources for its type. However, I’m not sure I like the “raw material counter” feel of this.

• Add player attributes that can be modified (e.g. health) so that e.g. death, or other effects-by-the-world can be supported.

Less grandly, I plan to work on one of these specific technical features soon:

• Allowing circuit blocks to be rotated to change their connectivity. (Right now, circuit blocks have specific faces — e.g. on a certain one the +X direction is always the output.)
• Figure out what more circuit primitives I want to add. (Right now, the circuits are definitely not Turing-complete, and not capable of all the effects on the world they should be, but there are also already a lot of different primitives; I may have to invent new block-picking UI just to make them practical.)
• Add moving objects (bodies) — things which can collide with the terrain as the player does. The current code is entangled with player behavior, and the player does not persist in a world.
• Add subworld/multiple-world handling — the ability for more than one world (grid of blocks) to be present in the same space. Right now, there are hardwired assumptions that the player is in the single world’s coordinate system.

Another core feature which is currently missing is the ability to design a blockset and then reuse it for multiple worlds. The problem right now is that we're using a simple object-graph serializer, so each world has its own blockset which is modified independently. To fix this, it needs to be possible to save a blockset under a user-visible name, and have individual worlds which reference that blockset; also, the world generator needs to decouple blockset generation from terrain generation. The “persistence” framework which added support for multiple worlds is a step towards this; the main thing I am pondering is what the semantics of these separate-named-persistent objects are and what the user interface for editing them is.

I upgraded to Mac OS X 10.7 Lion this month, and ever since then Cubes has crashed or otherwise misbehaved on my machine. However, I have only the one to test on, so I would like your help in figuring out what the extent of the incompatibility is — whether this is a GPU driver bug or something Cubes is doing wrong.

If you have a WebGL-capable browser (such as Chrome or Firefox) and GPU, and especially if you're running Lion or are otherwise similar to my configuration, please run Cubes (no installation is required) and tell me whether it works and what your system configuration is, including these properties:

(For some MacBook Pro models such as mine, the GPU used (9600M or 9600M GT) depends on the “Graphics” setting in Energy Saver preferences.)

The problems I observe are:

• All blocks (terrain) being flat white except for lighting; the sky and particle effects still have color. (For the interested, this appears to be a mis-execution of the over-unity-to-white code introduced in commit 48674f….)
• After some amount of usage, a crash (in Firefox, the browser exits; in Chrome, the display goes gray and the Web Inspector console says “WARNING: WebGL content on the page might have caused the graphics card to reset” while the in-page text says “Previous GL errors: INVALID_OPERATION”).

I will appreciate any help as this is making it quite impractical to work on Cubes.

In September, I wrote of my new project Cubes that “unfortunately, it wasn't an idea for either of my course projects this semester.” Since I have completely failed to find motivation for the course-related project I had planned to do, þreader (a thread-emphasizing feed reader; you can read the project introduction), I have decided to make the best of it and somehow make Cubes into the needed project.

I will therefore be using Cubes as my project for the course CS459 Human-Computer Interaction; the main consequence of this is that I need to actually study the potential users of my system.

So. To recap, Cubes is a block game (like Minecraft) where the blocks are made out of blocks; in principle, you should be able to build a complete custom block game from scratch simply by building the appropriate block-set, out of blocks. If you're a potential user of a game like this, and interested in giving me data (surveys, interviews, etc.), let me know. I will have something for you within the next few days.

Also, the live version of Cubes now supports load/save (either to Local Storage or by cut-and-paste of text (!)), so you can save your work! (I don't promise not to change the world format incompatibly, though.)

For a project I'm considering, I took a few hours to see if I could write a working garbage collector.

This is a very bare-bones copying GC, written without any reference to How To Do It Properly (just my knowledge of how a copying GC works, but I believe it is mostly cleanly written other than (a) the hardcoded pointer comparisons for object layouts, and (b) support for exactly one GC root, which happens to be the object at the lowest address. (It also calls a “heap” that which I believe is conventionally called a “space”. And I suppose someone could take issue with my placements of casts and void *s.)

The test program simply allocates a structure containing the strings “Hello” and “world”, allocates a bunch of junk, and then prints the strings to show that they are still intact.

Varychase is a graphics toy I just published. Runs in the browser; wave your mouse around and it makes curly patterns.

I originally wrote the option-less version May 29, 2010; yesterday I finally got around to adding a bunch of stuff, polishing the presentation, and publishing it.

It uses <canvas> for the optional line-drawing (I should compare the performance to using SVG instead, as well as also putting the dots in the canvas), and a few miscellaneous HTML5/CSS3 features for optional refinements. I've tested in Safari, Chrome, and Firefox on Mac.

I forget why I wrote this Haskell program, but it's cluttering up my do-something-with-this folder, so I’ll just publish it.

-- This program calculates all the ways to combine [1,2,3,4] using + - * / and ^
-- to produce *rational* numbers (i.e. no fractional exponents). (It could be so
-- extended given a data type for algebraic numbers (or by using floats instead
-- of exact rationals, but that would be boring).)
--
-- Written September 7, 2009.
-- Revised August 25, 2010 to show the expressions which produce the numbers.
-- Revised August 26, 2010 to use Data.List.permutations and a fold in combine.
-- 
-- In the unlikely event you actually wants to reuse this code, here's a license
-- statement:
-- Copyright 2009-2010 Kevin Reid, under the terms of the MIT X license
-- found at http://www.opensource.org/licenses/mit-license.html

I'd include the output here, but that would spam several aggregators, so I'll just show some highlights. The results are listed in increasing numerical order, and only one of the expressions giving each distinct result is shown.

(1 - (2 ^ (3 ^ 4))) = -2417851639229258349412351
(1 - (2 ^ (4 ^ 3))) = -18446744073709551615
(1 - (3 ^ (2 ^ 4))) = -43046720
(1 - (4 ^ (3 ^ 2))) = -262143
(1 - (4 ^ (2 ^ 3))) = -65535
...all integers...
((1 - (2 ^ 4)) * 3) = -45
(((1 / 2) - 4) ^ 3) = -343/8
((1 - (3 ^ 4)) / 2) = -40
(1 - ((3 ^ 4) / 2)) = -79/2
(1 - ((3 ^ 2) * 4)) = -35
...various short fractions...
(1 / (2 - (3 ^ 4))) = -1/79
(((1 + 2) - 3) * 4) = 0
(1 / (2 ^ (3 ^ 4))) = 1/2417851639229258349412352
(2 ^ (1 - (3 ^ 4))) = 1/1208925819614629174706176
(1 / (2 ^ (4 ^ 3))) = 1/18446744073709551616
(2 ^ (1 - (4 ^ 3))) = 1/9223372036854775808
(2 ^ ((1 - 4) ^ 3)) = 1/134217728
...various short fractions...
(((3 ^ 2) + 1) ^ 4) = 10000      (the longest string of zeros produced)
...all integers...
(2 ^ (3 ^ (1 + 4))) = 14134776518227074636666380005943348126619871175004951664972849610340958208
(2 ^ ((1 + 3) ^ 4)) = 115792089237316195423570985008687907853269984665640564039457584007913129639936
Tried 23090 formulas, got 554 unique results.

(If anyone has already used this title, that wasn't my intent.)

“Fire Worms From Outer Space!” was a game I wrote in spring 2009 as my final project for PH115 Science of Multimedia at MVCC.

It was written in Macromedia Adobe Director, and designed as “with the structure of a shoot-em-up and the mechanics of a physics game”; you must defeat the enemies in each of a series of levels — by smashing apart their chains-of-spheresical bodies with your wrecking ball of an inexplicably orbiting asteroid.

Most of the development time was focused on getting the physics right; the graphics, sounds, and level design were all secondary.

(I'm not particularly a fan of Director; it's just what was used in the class. If I ever get around to it, I'll rewrite it in JavaScript.)

Play Fire Worms

• Play on web (requires Shockwave plugin)

  (Please let me know if this doesn't work; I don't have the Shockwave plugin so I can't test it.)

• Mac OS X app (standalone)
• Windows app (standalone?)

Source

The Director file, plain-text copies of the scripts, and all of my saved development history (reconstructed; it was originally a bunch of directory copies) are available in a Git repository at git://switchb.org/fire-worms/. (No web view yet; need to do that.)

Other than the background image, credited in game and in “Title Page” to NASA, all elements of the game are Copyright 2009 Kevin Reid. I haven't gotten around to sticking a license on it; contact me and I'll get around to labeling it MIT or CC — let me know what license would be useful for what you'd like to do with it.