Background

I’m working on a browser-based game engine that uses Three.JS for rendering and a WebAssembly port of the Bullet physics engine called ammo.js for its physics engine and character controller.

Bullet is a very old physics engine and Ammo.JS is more or less a direct copy of it with a few changes to support usage in the browser. There are a lot of rough edges and things you have to figure out yourself in order to use it.

I recently finished some work involving constrained bezier curves for use in my browser-based digital audio workstation. Specifically, I used them in its envelope generator, which looks like this:

The circles are draggable handles that allow the user to create whatever shape they desire for the envelope. The green handles define the start and end point of each curve segment and the blue circles control its shape/steepness.

The Problem

In my project built with Rust compiled to WebAssembly, I started seeing errors like this that caused a crash - but only when it was compiled in debug mode:

wavetable.wasm-011dbbd6:0x17b89 Uncaught RuntimeError: memory access out of bounds
    at wavetable.wasm._ZN9wavetable2fm7effects14EffectInstance10from_parts17h321e4433e1216e56E (wavetable.wasm-011dbbd6:0x17b89)
    at wavetable.wasm._ZN9wavetable2fm7effects11EffectChain10set_effect17h969349e414104e9eE (wavetable.wasm-011dbbd6:0x1ba60)
    at wavetable.wasm.fm_synth_set_effect (wavetable.wasm-011dbbd6:0x314d3)
    at FMSynthAWP.port.onmessage (FMSynthAWP.js:171:37)

When compiling in release mode, the code ran just fine.

The decompiled debug-mode Wasm at the point of the crash looked like this:

I have some very basic Cypress tests set up for one of my personal projects - a single-page application created with React. I have some simple Github Actions configured to automatically run those tests every time I push to the repository.

At some point somewhat randomly, those tests started failing in CI. It was probably due to some dependency getting upgraded or a change in the environment in which Github Actions runs. The tests still ran fine locally when using the same commands and configuration, though, and I struggled to figure out why.

I’ve recently set up a Bluesky Personal Data Server (PDS) to store the data for my Bluesky account. I wanted to host it on my server alongside the many other web apps, databases, and many other services. I additionally wanted to use my top-level domain as my handle.

I started out following the install guide on the official PDS repo and it initially started out pretty well. However, I pretty quickly ran into some issues where the default config didn’t work for me.

The Problem

I was working on a screen-space reflection shader. This involves reading pixels out of the main scene’s framebuffer/texture to be reflected.

I was seeing strange grainy-looking artifacts showing up in my reflections that I couldn’t trace to anything in my shader code. Here’s what they looked like:

Triplanar Mapping is a method I make use of all the time in my 3D projects. Over time, I’ve experimented with tweaks and alterations to it with the goal of making it look better, run more performantly, and be useful in more situations.

The main change I present here is switching from using a linear mix of texture weights from each axis to a non-linear mix.

To explain what I mean by this, I’ll just show some code.

I regularly use Graphviz to generate… graph visualizations. Since my website and blog are all dark-themed, I usually want to set it up so that the generated SVG is dark-themed as well.

Here’s the basic config I use to make graphviz produce outputs with dark backgrounds and light content:

digraph G {
  bgcolor="#181818";

  node [
    fontcolor = "#e6e6e6",
    style = filled,
    color = "#e6e6e6",
    fillcolor = "#333333"
  ]

  edge [
    color = "#e6e6e6",
    fontcolor = "#e6e6e6"
  ]

  # The rest of your code goes here...
  A -> B;
  B -> C;
  C -> A;
}

That results in an output that looks like this:

Recently when working with the regl WebGL wrapper library, I encountered a weird error that I didn’t understand the cause of:

(regl) invalid dynamic attribute "position" in command

I checked my code, and I was indeed passing a position attribute and the data array I was using to construct the buffer looked correct. The error also happened intermittently, happening after my application hot-reloaded.

The Cause

It turns out that I had accidentally created two regl instances and was trying to use buffers allocated on one with commands created on a different one.

I was working on a new SvelteKit project with Svelte 5 recently, and I kept getting an error that prevented anything from loading in the browser:

[vite] Pre-transform error: Failed to load url __SERVER__/internal.js (resolved id: /Users/casey/osu-embeddings/frontend/.svelte-kit/generated/server/internal.js) in /Users/casey/osu-embeddings/frontend/node_modules/@sveltejs/kit/src/runtime/server/index.js. Does the file exist?
[vite] Error when evaluating SSR module /node_modules/@sveltejs/kit/src/runtime/server/index.js: failed to import "__SERVER__/internal.js"
|- Error: Cannot find module '__SERVER__/internal.js' imported from '/Users/casey/osu-embeddings/frontend/node_modules/@sveltejs/kit/src/runtime/server/index.js'
    at nodeImport (file:///Users/casey/osu-embeddings/frontend/node_modules/vite/dist/node/chunks/dep-DkOS1hkm.js:55067:25)
    at ssrImport (file:///Users/casey/osu-embeddings/frontend/node_modules/vite/dist/node/chunks/dep-DkOS1hkm.js:54976:30)
    at eval (/Users/casey/osu-embeddings/frontend/node_modules/@sveltejs/kit/src/runtime/server/index.js:5:37)
    at async instantiateModule (file:///Users/casey/osu-embeddings/frontend/node_modules/vite/dist/node/chunks/dep-DkOS1hkm.js:55036:9)

The Cause

It turns out that I had a broken symlink in my static/ directory. I had cloned the project down to a new computer, and the file only existed on the old one.