Jun 9, 2024
Here's the most recent bugfix I had to make, along with a fairly lengthy but still incomplete post-mortem in the commit description.

Still several things left to investigate.

  • Really small windows probably crash.
  • Really wide and short windows probably crash.
  • Pressing and releasing mouse really quickly within a single frame will probably crash.

I want to delete some data structures and just recompute them all the time.

permalink

* *
Jun 7, 2024
All the bugs in my software that others run into have the following story template:

  • t = n: my program was responsible for x and y
  • t = nn: my program became responsible for x, y and z
  • t = nnnnnn: bug in z (interacting with x/y)

Adding z required rethinking the entire program. I tried to patch it in. Implications were not fully worked out.

permalink

* *
Jun 5, 2024
Trying to build software for others is extremely disheartening. I can be eating my own dogfood on a daily basis for years and still newcomers hit bugs in their first 10 minutes.

I wonder if this is the major reason to huddle together on top of jenga stacks with tons of dependencies, terrified of fragmentation: You always need more testing than you think, and there's no way to compete with something that's been through that much testing.

I come stare at this abyss every year or two.

Doesn't do me any good, though.

(This post spawned a sprawling, constructive conversation.)

permalink

* *
May 4, 2024
Visualizing the digits of π

The following program lets you scrub the mouse downward to find more and more precise approximations of π within the red optical sight in the center of the screen.

permalink

* *
Apr 24, 2024
I've been idly looking at the space of possible rules for 1-D cellular automata.

To recap, you basically have a line of cells that can be in one of two states ('alive' or 'dead') and rules that decide how a cell's state evolves based on the state of its immediate neighbors to the left and right. The images below show a snapshot of time in a row of pixels, and time advancing from the top row of pixels to the bottom.

Starting from a single live cell, of the 256 rules 16 immediately wink out (empty grids in the picture below), 16 don't change (vertical lines), 48 move the cell (24 each to the left and right), 30 grow into triangles over time (6 each to the left and right and 18 on both), 18 form Sierpinski patterns and 22 are more chaotic. Here's a detail in Lua Carousel where you can see many of these types.

Detail of Lua Carousel browsing the space of possible rules for 1-D cellular automata, with each rule starting from a single live cell and rows further down showing its evolution over time.

However, things look different if you start from a random configuration of live and dead cells. Seemingly well-behaved rules hide subtleties, and seeming patterns vanish.

The same rules as above, but now we're starting from the same random configuration in each rule.

For a given rule, different random initial configurations largely look the same from a distance, which suggests random selection yields more realistic pictures for a rule.

Eye-balling the surface, I think 47/256 rules are chaotic.

Rule 30 is the famous one, but my favorites are rule 150 and 165.

Detail of Lua Carousel focusing on the Rule 150 1-D cellular automaton.

(I've also been skimming Stephen Wolfram's "A New Kind of Science" as I do this. Wolfram separates "nested" from "random" patterns, but that seems to be an artifact of starting with a single live cell. "Nested" patterns (like Sierpinski triangles) are just a milder kind of chaos our visual cortex can get a grip on.)

Starting with a single live cell is 'simple' but grossly incomplete, exercising only scenarios 0, 1, 2, and 4 in the first step.

A couple of generations under high-magnification, showing that a single live cell exercises only 4 rules (each highlighted in a different color).

And if we truly care about simple, why not just start with all dead cells? Rules don't care.

Anyways, I see two fairly simple initial states that exercise every possible scenario in time step 1: the mirror images 10111 and 11101 when surrounded by runs of dead cells.

Now I see only the one real stable rule: rule 204. 204 is binary 11001100, each bit of which is exactly the middle bit of numbers 7-0. In other words, every scenario maps to the central square.

Detail of Lua Carousel showing rule 204. Clear vertical lines down the center show that each generation is identical to the last. You can also see rule 236 poking out near the bottom. It too stabilizes to identical generations, but if you squint the first generation isn't identical.

Even here, though, the long runs of dead cells keep the "true nature" of a rule from coming out. I think random initial conditions do that much better.

Perhaps what would be best is to keep our simple pattern in the center exercising all scenarios, and then pad it with a random initial state. We do have to remember to pad it out with 3 dead cells. Let's do that on both sides for symmetry.

Ah, here's a nice screenshot of a central portion of the ruleset, ideal density for chaos to emerge.

A detail of Lua Carousel running a browser of the 1-D cellular automata. We're zoomed out enough to see 20 rules at once, with others partially visible on the fringes. Fully visible is the rectangular subset centered on rule 151. We're laying out the rules in a 16x16 grid, so the visible rules are 133-137, 149-153, 165-169, 181-185. Even at this zoomed-out scale, rules 135, 137, 149, 150, 151, 153, 165, 169, 182 and 183 are visibly chaotic.

Links

permalink

* *
Apr 19, 2024
The kids got a choose-your-adventure Oregon Trail book from the library, and I got nerdsniped into making a map for it.

(It's easy to get me to do something if it involves opening snap.love)

A tree summarizing a choose-your-adventure book. Each box has a page number, and you can visualize how the choices each page offers.

After finishing the map, I've been paying attention to the "meta game" of manually adjusting box positions and widths (height depends on amount of text) to make the arrangement pleasing to the eye. Constraints I've grown conscious of during this process:

  • Lining up child nodes vertically
  • Lining up nearby nodes. (imperfectly)
  • Avoiding long edges.
  • Keeping nearby edges approximately the same length.

I'd appreciate if anything seems jarring in this image, or if you have new OCD rules to infect me with :)

One frustration: I spent a while adjusting widths of boxes to not wrap lines within words, only to find that adjusting zoom messes things up again. This is an old problem: I can have precise scaling or crisp text, but not both. All my apps choose the latter.

permalink

* *
Apr 15, 2024
I'm reading a paper on my phone in bed and see this problem:

Convolving a list with itself. Given a list [x1, x2, ..., xn−1, xn], where n is unknown, construct [(x1, xn), (x2, xn−1), ..., (xn−1, x2), (xn, x1)] in n recursive calls.

And I am able to switch apps and solve it right on my phone, without needing to get out of bed.

I do have to put up with some klunky (Lua) syntax, though.

permalink

* *
Apr 13, 2024
New convivial platform just dropped

Looks like it's a fork of emscripten augmented to compile a whole OS kernel and userland. Includes raylib for graphics, and Lua bindings to it so I feel at home. Seems easy to build so I'm comfortable depending on the hosted version.

There's an app store anyone can publish apps to. Your changes remain in your browser's local storage until you publish them. All apps in the app store are mounted on the file system under /usr/store so it's easy to look at their source code.

Here's a port of one of my early LÖVE apps, for geometric constructions. It's on the app store so anyone should be able to run it just by clicking on this link.

Disclaimers. It's slow. Still lots of bugs. I had to reboot the VM several times while recording this video. Commands often hang or crash, then completely stop working until I reload. It's never lost my data, though. (Data is stored in local storage.)

permalink

* *
Apr 2, 2024
Drawing histograms

screenshot of Lua Carousel drawing some histograms

From the Lua Carousel devlog.

permalink

* *
Mar 29, 2024
The simplest possible dither

"Add noise then quantize."

From the Lua Carousel devlog.

permalink

* *
archive
projects
writings
videos
subscribe
Mastodon
RSS (?)
twtxt (?)
Station (?)