Tuesday, November 23, 2021

Stability and versioning: Lock yourself in at your own peril.

I usually write about Rust, but today I want to discuss something broader; flexibility in software, particularly in design and architecture. To begin, let's focus briefly on versioning.


Prior to semantic versioning, version numbering conventions used in software releases were nearly as numerous as the releases themselves. Some had implied meaning for releases with odd vs even numbers, some would skip numbers arbitrarily, some would use letters and other non-numeric characters, and some would have unique counting strategies. Semantic versioning provided some much-needed consistency.

Consistency, however, is not the ultimate goal. You might imagine some issues with consistency itself; is it better to have some inconsistencies (mix the good with the bad), or just be consistently bad? One of the most important goals for a software maintainer is to provide repeatability; in other words, consistency within your build process and testing infrastructure. Same word, just scoped differently. Versioning, when used appropriately, can help increase the repeatability of your builds and tests.

So then, let's defined "appropriate versioning". If we follow SemVer closely, then it should not be possible to introduce breaking changes in our software that will negatively impact downstream dependents. If a mistake is made and a breaking change goes out in a version that is not a semantically breaking version, then we have to do the right thing and unpublish/yank the semantically incorrect version. That's all there really is to it. I'll leave you to read the SemVer spec for the precise rules to follow, but this is all that one needs to appropriately version their software.


This term, "stability", is ironically such a fragile concept. For something to be stable, it must be unchanging. For something to be unchangeable, it must be perfect. Very few things are universally perfect. I like to use science to illustrate this point: the sciences are ever-evolving; knowledge is not static but accumulates and is refined over time precisely because it didn't start out perfect. It is fitting that computer science is one of these fluidly changing organizations of knowledge.

When software engineers think of stability, they are usually looking at it in the context of any of the following layers of abstraction:

  • API stability. This is what SemVer addresses directly.
  • ABI stability. The idea that binaries compiled long ago (or by different toolchains) should work transparently with binaries compiled today.
  • Resilience. Resistance to changing behavior or breaking compatibility, but also resistance to logic bugs and the like.

Resilience in service-oriented software is a very interesting topic of ongoing research, but we can frame resilience in the terms described above. Namely resistance to logic bugs, since changes in behavior or interface are better addressed through tools like SemVer.

So, what do we know about logic bugs in stable interfaces? The first thing that comes to my mind is in the C standard library. It's our old friend, the null-terminated string and its wild band of merry havoc-wreaking unsafe functions! There is good reason this has been dubbed the most expensive one-byte mistake. Now just because C has null-terminated strings and its standard library supports them doesn't mean you have to use these abominations even if you write code purely in C. But the sheer support for them in the wider ecosystem sure does make it harder to integrate various libraries when you are using any of the safe alternatives. Not to mention the fragmentation that each of those contributes to.

We are left with a stable interface whose intractable design makes it almost useless in practice. It may as well not exist at all! We'd be better off without null-terminated strings, de facto. But in some sense, we are stuck with them for all time, and there is nothing that I, you, or anyone else can do about it. This is clearly a highly important lesson of stabilization.

There is another term for stability, often used with critical connotation:


No doubt, many will first encounter this term when trying to understand the QUIC protocol. It has been used in various circles for far longer, though.

If you read between the lines a little, ossification sounds like an objectively bad thing. It is outside of your control, and you cannot fix it. What could be worse than that? In my opinion, being the decisionmaker in that case would be worse. I wouldn't want to be held accountable for saying "this is our call; it's set in stone and it can never be changed."

Stability comes packaged with this gremlin called ossification, and they are inseparable. What sounds like a good idea right now may turn out to be a bad idea later. It happened with null-terminated strings and nullable pointers, it happened with PHP and Python, and it will happen again. Maybe the next library or application you stabilize will turn out to be totally wrong/broken/inadequate.

You can't tell the future, but you will definitely be stuck with the past.

Outside of standard libraries that ship with programming languages and compilers, it is a pretty safe bet that being totally wrong/broken/inadequate is a reasonable situation to be in; you just patch your library or application when things need to be fixed and all is right, right? I think this actually depends on a few aspects:

  1. The software maintainer needs to be on top of maintenance. If they fall behind on making patches or merging PRs, then you're left with the maintenance burden yourself, often on software that you are not an expert in. It just happens that you depend on its functionality and you get stuck with the bill when the maintainer moves on to other projects.
  2. Other dependents need to maintain their software, too! That means all transient dependencies in the entire tree need the same treatment and amount of prioritization to receive patches in a timely manner.

To echo the sentiment of the Fastly article, as long as everyone keeps up their end of the bargain with maintenance, there isn't a whole lot that can go wrong. It's just an impractical task to herd all of those cats; that's the reality.

What, then, is there to do about standard libraries? Hopefully as little as possible! Considering the likelihood of getting a design or public interface wrong, and the resistance to change with strong stability guarantees, it is in everyone's best interest that standards libraries be as small and self-contained as reasonably possible. Even some primitive types that are useful in general may be better off in a library that can freely be updated (in breaking fasion) by end users. Yes, I'm thinking of strings in C, again; but I'm also thinking about mutex poisoning in Rust; I'm thinking about Python's multiple XML interfaces and its asyncio module that is arguably poorly designed compared to curio and trio; I'm thinking about Go officially supporting largely irrelevant and insecure ciphers like RC4, DES, and MD5 (honorable mention to both pseudorandom number packages, because that's never going to confuse anyone).

Maybe it's better to not include everything in the standard library. We just end up hearing recommendations over an over about how you shouldn't use this feature or that function because it's unsafe/insecure/deprecated/there's a better alternative. Starting with a very small surface area seems like the right way to go. This is not a proposal to start small and grow gradually, though! I don't think a standard library should grow much, if at all.

Think about it this way: Something like JSON might seem like an obvious choice for inclusion now, but in 40 years, is anyone honestly still going to use JSON? I mean, ok, fine. People are still using COBOL. But my point is that 80% of all developers are not COBOL devs. In four decades, sure there will be some JSON stragglers just like there are some COBOL stragglers today, but I can't believe that it will remain popular considering how bad it is for so many reasons. (Let's face it! The only reason protobuf or something else hasn't entirely supplanted JSON is because web browsers have ossified their serialization format.) JSON will very probably end up like null-terminate strings; the bane of some seasoned developer's existence. They both seem just so innocent, don't they?

Be very cautious about what you choose to ossify.


I'm not much of a words-person, but when I research things that I write about, I usually go to the thesaurus often to find a good synonym for whatever concept I'm trying to convey. One of the top synonyms given for "flexibility" was "resilience"! And this was a fascinating discovery itself, worthy of a paragraph or two. Flexibility implies resilience because flexible things bend rather than break. When something is rigid and enough pressure is applied, it has to break at some point. And breaking is not very resilient, is it?

This definition of "bend rather than break" applies in a number of relevant ways for software design. A service provider strives for resilience to downtime and outages. A programming language designer and compiler implementer strives for resilience to breaking user code. Interface designers strive for resilience to footguns and obvious logic bugs. In each case, the person wants the software (or user) to bend rather than break.

I like it. In fact, I'm willing to boldly claim that resilience is objectively desired. If that is the case, then its synonym, flexibility, should also be just as desired, objectively. Among the definitions of this particular word, you'll find "bend rather than break", "ease of adaptation or offering many options", and (my person favorite) "the willingness to adjust one's thinking or behavior." Doesn't that last definition sound suspiciously like science and knowledge? It's no coincidence, and I'm not just playing word games. I'm pointing out the underlying truth that things must change. It's the third law of thermodynamics.

Any resilient system will necessarily resist ossification.

What are these quotes, by the way? Don't worry about it! I just made them up. If I used twitter, these are the kind of one-liners I would tweet. But I don't, so I don't. You have to read the longform, instead.

I have argued so far that the concept of "stability" has something of a duality. There's the notion that something is stable because it resists external change, and the notion that something is stable because it resists bugs; it resists stagnation. An example of the former is a strong interface stability guarantee from a library. An example of the latter is keeping your browser and OS up-to-date to fix bugs, known security vulnerabilities, and just to acquire new features. Or stated another way, the "it's not a bug, it's a feature" line of thinking is the bug.

Lock yourself in

Having set the stage for stability as a means to lock-in a design or set it in stone, let's dive in to that concept a bit more. There are some examples in package managers where "locking in" your dependency list is a normal best-practice. npm has a package-lock file and a ci command to install packages from it. Cargo has a Cargo.lock file and installs packages from it by default (top-level only). go.mod files have the same basic use.

I bring this up because versioning dependencies has been converging on this concept of locking the precise version number of every package in the tree within many major package managers. And it's no surprise, because this is one of the best tools for providing repeatable builds and testing. Semantic versioning plays right into that, as I covered earlier.

There's just one problem. This is not the kind of "locking in" that I allude to in the title. I'm talking about locking yourself into a specific design that is hard to change later. I'm talking about being that decisionmaker that owns the responsibility for putting a crappy middlebox on the Internet without ever updating it to support newer protocol revisions (or newer protocols, period). I'm talking about tying your hands by offering a stable API that just plain sucks. No, I take that back. I'm talking about tying your users' hands. Because it's not the author that is locking themselves into a contract. They are locking their users into a contract.

You may lock yourself in at your own peril, but you lock everyone else in with you at their peril.

This is something I take personal grievance with. Development philosophies like "worse is better" means that everything I use on a daily basis is worse than it could be otherwise. The Internet is held together with bubblegum and string. Wirth's law is real, and it threatens our very existence. I'll admit, using Wirth's law to criticize Bitcoin is a bit cheeky. But sometimes you just have to be cheeky.

I've rambled on enough, and linked to about a dozen articles that you should read. I'll just leave you with one last thought: Change or die.

Tuesday, July 27, 2021

Mutable statics have scary superpowers! Do not use them

In Rust, it is well-known that static mut is dangerous. The docs for the static keyword have this to say about mutable statics:

If a static item is declared with the mut keyword, then it is allowed to be modified by the program. However, accessing mutable statics can cause undefined behavior in a number of ways, for example due to data races in a multithreaded context. As such, all accesses to mutable statics require an unsafe block.

This makes perfect sense, so far. But my program is single threaded. I know it is single threaded because it runs on bare metal with no_std. I also know that I will need global state to manage access to memory-mapped I/O, and the global state needs to be mutable so that I can replace it at runtime. I can do this with static mut because I do not have to worry about data races with multiple threads right?

Well, that's the thought I initially had, anyway. And I believe I am not alone. But there is a lot of subtlety with static mut references that are problematic, even in a guaranteed single-threaded context. At first I believed it all has to do with the special 'static lifetime, but that is not the case. Rust By Example describes this lifetime as follows:

As a reference lifetime 'static indicates that the data pointed to by the reference lives for the entire lifetime of the running program. It can still be coerced to a shorter lifetime.

That also makes sense, and it's exactly what I want. In my case, the memory-mapped I/O that I wanted to control was a serial port. The primary goal was to reproduce something akin to standard I/O with println! and dbg! macros like those provided by the Rust standard library. A secondary goal was to make the sink configurable at runtime. This would allow the software to run on hardware with different serial interfaces, for example, without recompiling it for each distinct device.

The platform I was targeting is the Nintendo 64. Which, as you might guess, does not have your good old RS-232 serial port. It has a slot for game cartridges, and an expansion bus on the bottom which is basically just another cartridge port. It also has some controller ports on the front. Nothing really stands out as a plug-and-play means to get a serial console interface. As luck would have it, there are development cartridges that have an FTDI chip and USB port on them for exactly this purpose! The bad news is that each dev cart has its very own custom MMIO interface, and none of them are compatible.

Going back in time a bit, there are also debug interfaces on the original development hardware used in the 90's (and for a few years in the early 2000's) which use either parallel or SCSI ports. Some emulators support these interfaces because games (especially prototypes) actually print interesting things to them.

So we're in a situation where we want to write software for a platform (N64) that has a number of different serial interfaces available, but we don't want to build 3 or 4 different executables and put the burden on the user to figure out which one they need. And so here we are; we make the serial I/O implementation configurable at runtime. It can detect which interface is available, and that's what it uses. No sweat!

The core:fmt::Write trait

We want to use core::fmt::Write to make the implementation generic. This trait provides some useful methods for implementing the macros, and the core formatting machinery takes care of the details I don't want to think about. There are far better designs than what I came up with, but the initial implementation of my runtime-configurable I/O API would store a trait object (implementing fmt::Write) in a lazy_static. And the macros just needed a way to get a mutable reference to it. That's &'static mut dyn fmt::Write, mind you. But, I thought to myself, if I just hide all that inside the macro, nothing bad can happen!

What I didn't realize is that static mut has superpowers. I'll try my best to explain what these superpowers are, but please bear with me! I do not fully understand why these superpowers exist or what they are fully capable of. What I do know is that you never, ever, under any circumstance, want to anger them.

The 'static lifetime means that it lives forever (as far as the program is concerned) and making a static mutable means that you can only touch it in unsafe code, because threads and data races, right? Wrong! You need unsafe because the superpowers of static mut allow you to introduce instant Undefined Behavior. To explain, let's revisit what &mut means in the first place.

It's true that &mut allows you to change the contents of the thing behind it, but that's really just a side effect of the real purpose of &mut; it's an exclusive (unique) borrow. There can be only one.

All jokes aside, this is an invariant that you cannot break. Creating mutable aliases is instantly Undefined Behavior. Invoking Undefined Behavior gives the compiler license to do anything to your code. We really only want the compiler to do what we want it to do with our code, so let's just agree to avoid UB at all costs. To really nail this one down, consider what the Nomicon has to say about transmute:

  • Transmuting an & to &mut is UB.
    • Transmuting an & to &mut is always UB.
    • No you can't do it.
    • No you're not special.

There is some subtlety here that I won't go into, but the core of the issue is that this creates mutable aliases. Don't do it!

A starting point

There are some things that you will naturally begin to intuit while writing Rust after you have been using it for a while. It's helpful to recognize things that will cause the borrow checker to reject your code, for example. A quick internal borrow check in your brain can save a few seconds (or minutes, in extreme cases) of compile time just to be provided with an error message.

Let's begin with this bare minimum State struct:

#[derive(Copy, Clone, Debug)]
struct State {
    x: i32,

impl State {
    const fn new() -> Self {
        Self { x: 0 }

    fn get_mut(&mut self) -> &mut i32 {
        &mut self.x

There is nothing really special here, so far. You can gain a mutable reference to the x field if you have mutable access to the struct. Standard stuff, so far. If you attempted to write code like the following, it might make you pause as your internal borrow checker raises a red flag:

fn main() {
    let mut state = State::new();

    let a = state.get_mut();
    let b = state.get_mut();

    *a = 42;

    println!("I have two i32s: {}, {}", a, b);

Importantly, it isn't the explicit dereference (*a = 42;) that trips the borrow checker, here. It's the println! macro. And the error message illustrates this perfectly:

error[E0499]: cannot borrow `state` as mutable more than once at a time
  --> src/main.rs:22:13
21 |     let a = state.get_mut();
   |             ----- first mutable borrow occurs here
22 |     let b = state.get_mut();
   |             ^^^^^ second mutable borrow occurs here
23 | 
24 |     println!("I have two i32s: {}, {}", a, b);
   |                                         - first borrow later used here

This mutable aliasing issue is something I've become more aware of over time, so it's kind of silly for me to write examples like this. The demonstration does help prove my point about superpowers though.

Let's make it static

Using the same State struct from above, let's make some minor adjustments to the program that uses it, so that State becomes static:

static STATE: State = State::new();

fn main() {
    let a = STATE.get_mut();

    *a = 42;
    println!("I have one i32: {}", a);

Your internal borrow checker should raise another red flag, here. We made the state static, but not mutable, so we cannot compile this code:

error[E0596]: cannot borrow immutable static item `STATE` as mutable
  --> src/main.rs:20:17
20 |         let a = STATE.get_mut();
   |                 ^^^^^ cannot borrow as mutable

Everything is as expected so far. We need to make the static state mutable so that we can borrow it mutably (exclusively, remember). And that also means we need to use the unsafe keyword. We're about to find out why it's actually unsafe. :)

static mut STATE: State = State::new();

fn main() {
    unsafe {
        let a = STATE.get_mut();

        *a = 42;
        println!("I have one i32: {}", a);

Well, that's not so bad! My internal borrow checker can't spot anything wrong with that. And neither can the compiler's (much better) borrow checker:

I have one i32: 42

But now I want to get spicy! 🔥 I want two exclusive references to the same memory. Or maybe I don't, but it accidentally happens anyway.

static mut STATE: State = State::new();

fn main() {
    unsafe {
        let a = STATE.get_mut();
        let b = STATE.get_mut();

        *a = 42;
        println!("I have two i32s: {}, {}", a, b);

My internal borrow checker says this cannot work, just like it didn't work before. And the Rust borrow checker is way better than mine, so surely it won't allow this!

I have two i32s: 42, 42


(╯°□°)╯︵ ┻━┻

To be fair, trying to run this code in miri does detect the Undefined Behavior. This is a very powerful tool, along with the sanitizers. Always use these when you are writing unsafe code! No exceptions. This is a huge relief, or at the very least it's better than nothing. Here's what miri finds:

error: Undefined Behavior: no item granting write access to tag <2843> at alloc1 found in borrow stack.
  --> src/main.rs:23:9
23 |         *a = 42;
   |         ^^^^^^^ no item granting write access to tag <2843> at alloc1 found in borrow stack.

Still, you may be caught off guard by this. Don't worry, it's a perfectly normal reaction. We didn't fundamentally change the State implementation, and yet putting it into a static mut changes its semantics. We might be given a hint about why this is if we desugar the get_mut method's function signature:

fn get_mut(&'static mut self) -> &'static mut i32

Go ahead, try it out! It compiles just the same. The static lifetime was simply elided. But wait, what if we keep this 'static lifetime and go back to the safe program code that puts State on the stack?

error[E0597]: `state` does not live long enough
  --> src/main.rs:21:13
21 |     let a = state.get_mut();
   |             ^^^^^----------
   |             |
   |             borrowed value does not live long enough
   |             argument requires that `state` is borrowed for `'static`
31 | }
   | - `state` dropped here while still borrowed

So it is true that the 'static lifetime is special. We cannot borrow State for 'static because State lives on the stack. We would have to move it to the heap and leak the reference to make it live for 'static if we wanted to call the method with this lifetime bound. However, we cannot create mutable aliases in safe code with leaked boxes because they are not static.

In the case of static mut, we're allowed to borrow with a 'static lifetime, but we're also allowed to exclusively borrow multiple times. If you could only exclusively borrow a static mut once, it would make the feature useless for many valid cases. And this is the tricky part that, at least in my mind, makes static mut such a nightmare. You don't have a choice but to ensure the invariant that mutable aliasing does not occur, but the compiler won't prevent you from doing so. It is particularly insidious when your safe interface allows reentrancy, and that's how I hit this problem. Nested dbg! macro calls are pretty common.

This is the superpower of static mut.

How did I fix this in my configurable serial I/O?

Well, I'm not entirely sure that I did, to be honest! But I did find a way to get my macros to receive an exclusive borrow with a lifetime shorter than 'static. And I did that by not borrowing a static mut. Instead I have statics with interior mutability (STDOUT and STDERR). I opted to use spin::Mutex<RefCell<T>> to keep my uses of the unsafe keyword to a minimum, but it's also possible to store state with interior mutability in a static UnsafeCell. This is the recommended replacement according to Consider deprecation of UB-happy `static mut` · Issue #53639 · rust-lang/rust (github.com)

I also had to jump through hoops to get trait objects working without Box, but that was another rabbit hole entirely. In the end, I learned a valuable lesson about static mut and how bad it is for your health (and mine!) There are ways to make it work that are trivially safe, but reading through that GitHub ticket ought to ruffle your feathers, even if I haven't already convinced you that static mut probably should not be used.

Saturday, June 13, 2020

The Rust compiler isn't slow; we are.

This might be a bit of an unpopular opinion, so the clickbait title should be appropriate!

I've been learning and using Rust for nearly four and a half years, since version 1.6. That's a good amount of time to become familiar with some of the troubles of the language, the tooling, and the ecosystem. But this is a slightly different story, this is a dissent to a common criticism that the compiler is slow. In this discussion, I will argue that these claims are misleading at best.

Screenshot of Activity Monitor showing rustc using 100% CPU
rustc compiling a non-trivial application.

There is plenty of evidence that suggests rustc is slow relative to compilers for other languages; Go can compile applications with similar complexity in 1/5 the time, and clang or gcc can do the same for applications written in C. It might be acceptable to justify that the Rust macro and type systems are significantly more complex than what is usually written in either Go or C, and that it warrants much heavier lifting by the Rust compiler. While there is some truth in that sentiment, I believe there is more to it than that. I believe it's more of a human problem than an algorithmic one.

Friday, November 3, 2017

Tiny MCU 3D Renderer Part 10: Benchmarking, profiling, and optimizations

The reason I have been so quiet recently is because I've been working on a very dry subject; testing. Unit tests are probably the most uninteresting thing I do on a daily basis as a software architect. Create some fixtures, write some assertions, run the test suite, fix any issues, repeat. It makes me cringe, just thinking about it.

But here I am, blogging about how I've been writing tests in my fun personal project, too! I am taking this project very seriously, so tests are a necessary evil. I haven't checked coverage yet (because I hit this bug with tarpaulin vs serde_derive), but it's probably somewhere around 70~80%.

Update 2017-11-05: serde_derive is only used in the app. The lib doesn't have this dependency, so I can run coverage on the lib separately. The result is even better than I imagined: 85.14% coverage, 573/673 lines covered

Surprise! There are only 26 tests (ignoring the 4 benchmark tests), how can coverage to be so high? This is one of the most interesting things about 3D rasterization; it doesn't require a whole lot of code! To be honest, though, I'm only exposing the bare minimum set of APIs; for example there's no support in the fixed function pipeline for stencil/scissor, alpha blending, etc.

Saturday, October 14, 2017

Tiny MCU 3D Renderer Part 9: Bug fixes, and first shader tests

It's shader time! I finished the simple sunbeam, which I think looks quite nice in motion.

It could use a little work on the gradient, and some extra geometry wouldn't hurt. There are four sunbeams in this test scene. Each is just a plane (two triangles). I'm thinking of splitting the plane into thirds (vertically) so I can shape it more into a semi-circle, instead of just laying flat in the background. That might give it some depth, and help combat the problem with the right-most sunbeam looking so thin.

Monday, October 9, 2017

Tiny MCU 3D Renderer Part 8: Programmable Pipeline and Asset Pipeline

Oh hey, look at that! I changed the CSS on my blog a smidge. It's worth mentioning, anyway. Say hello to the Blipjoy Invader! You can just make it out on the left side, there. (Depending on your screen resolution, it might be behind the post content, whoops!)

I also finalized the programmable pipeline on the 3D renderer, thanks to @vitalyd over at the Rust user's forum for the hint I needed to push me in the right direction. The API isn't exactly what I had in mind, but it's certainly reasonable.

This is what I built yesterday. The model on the left is drawn with our very familiar Gouraud shader with interleave dithering on a four-color gradient. This is what we've seen exclusively in screenshots to this point. On the right is something new! A much simplified shader that renders something like a cartoon, aka cel shading minus edge detection. Each model rotates in opposite directions for funsies.

Code from the last article will be referenced below.

Wednesday, October 4, 2017

Tiny MCU 3D Renderer Part 7: Generics and Traits, oh my!

If you've been following my blog, you'll know that I've been writing a 3D renderer in Rust. This is my first real experience using the language. I dabbled a bit in Rust on a project in January 2016, where I was challenged by lifetime annotations, and gave up. This time around, I've managed to write a complete software renderer with all the bells and whistles of a modern shader model, without the need for a single lifetime annotation. And until just recently, without defining a single Trait or Generic.

Earlier articles in this blog series have focused exclusively on the renderer from an end user's point of view. In other words, trying to make it attractive to the everyday gamer. In this episode, I want to describe in detail one of the issues that I have been struggling with in the code design, and how I've been approaching a solution. This is by no means the "right way" to handle this, or even similar situations. I just want to provide some info for anyone who happens upon the right magical incantation in The Googlies, and ends up reading this.

(Edit 2017-10-04: The illustration below was originally flipped vertically. It now shows the correct scanning direction.)

Triangle rasterization scans pixels in the target buffer from left-to-right and bottom-to-top

So let's start from the middle, and work our way out. Above is a simplified representation of the rasterization step of the renderer. The details prior to, and those that follow rasterization can be ignored for the time being.

This image represents a zoomed-in detail of a frame buffer (or any render target) as a 2D triangle is being rasterized. This occurs after the perspective division, so the Z coordinate can simply be dropped for rasterization; the Z component is used later for depth testing.

Sunday, September 24, 2017

Tiny MCU 3D Renderer Part 6: Camera animation and display scaling

Yesterday I finally got around to adding some simple animations. The app was always rendering at 60 fps, but the image was static because there was no animation. That's why I've only been posting PNG images of progress so far. But now I can do this:

This was my first ever foray into quaternions! And I must admit, learning about quaternions suuuuuuucks. Surprisingly, this is one area where I would actually recommend developers keep quaternions as a mysterious black box, though an essential part of their repertoire. Every academic writing you will find about quaternions is deep in imaginary number territory (which we all know is impossible to represent on a computer). The important point is that the imaginary numbers can be optimized out, so having them in the first place is completely stupid, but I digress. Ok, ok, imaginary numbers help make sense of the derivatives... So what? It still sucks. And it's still pointless in the context of 3D graphics.

Sunday, September 17, 2017

Tiny MCU 3D Renderer Part 5: Aspect Ratio and Field of View

I had a long week on vacation, and was able to do a little bit of coding almost every night. There was a lot of time spent doing touristy things, so my coding opportunities were limited. I had a good solid 4 hours of nothing but coding time on the plane, though! Both ways.

On my departure flight, I managed to finally fix the aspect ratio (as far as I can tell). This was just a matter of adjusting the projection matrix to use the correct aspect ratio for non-square pixels. On my return flight, I finished almost all of the refactoring for the new Shader API, and finally completed it from the comfort of my own couch.
It shouldn't look too much different from the previous screenshot. There are a few obvious differences if you look closer, though.

Monday, September 4, 2017

Quick update, progress report, current plans

This weekend I was distracted by a well-intentioned good friend of mine who suggested solving a chess puzzle described as "deceptively simple". Unfortunately, the article is criminally misleading. Therein it is claimed that computers cannot "solve the conundrum quickly and efficiently". The article is misleading because it is in fact trivial to solve the puzzle in linear time with constant space complexity.

Solving the puzzle is not the challenge alluded to. The challenge is that given any starting position with queens already placed, find a valid solution by adding more queens. A notable related problem is enumerating and counting all valid solutions. To date, it has been shown by brute force that a 27x27 chessboard has over 243 quadrillion solutions; removing all symmetrical solutions results in about 29 quadrillion. The brute force work took about 7 years with a massively parallel array of custom hardware (written to FPGAs).

To provide some context to the size of the numbers involved, it would take a modern CPU (single-core at 4.5 GHz) about 4 years just to increment a counter as fast as possible from 0 to 29 quadrillion. That is the time estimate just for the work involving the counter; nothing more. It's also hopelessly optimistic, since that assumes you already have a list of all 29 quadrillion solutions, or that there are zero false positives or any instances of wasted effort.

Sunday, August 20, 2017

Tiny MCU 3D Renderer Part 4: Gouraud Shading

Today, it's interpolating normals to render smooth lighting. That's right; Gouraud Shading in full effect. Two screenshots to start with; first is a view with diffuse disabled, to show the full effect of the shading. Followed by fully textured.
Surprising that the texture is so dark. But it is what it is. I think this test model has just about reached the end of its usefulness for the project. There's just one duty left for it to serve. Remember those gradients at the bottom of the image that were added in Part 2? It's time to put our friend here through some post-processing!

Saturday, August 12, 2017

Tiny MCU 3D Renderer Part 3: Textures and Perspective

I was surprised by how easy it was to interpolate over the texture coordinates, given the barycentric coordinate space. I have more boilerplate code to convert the mesh vertices into cgmath vectors than there is code to interpolate the triangles! I'll refactor it all away after the renderer's features begin to stabilize. With a little gamma and luminance love, I now have nearest-neighbor texture mapping:
The gamma correction was crucial, since this texture went through two separate processing passes; first, I dropped all chrominance information from the RGB leaving just the relative brightness; and second the global illumination was applied to the texture mapped geometry as you might imagine. To get it working right, the RGB components are transformed from Gamma Space to Linear Space prior to the luminance transformation. Then the texture stays in Linear Space until after the final illumination pass. The pixels are transformed back to Gamma Space as they are written to the frame buffer.

Friday, August 11, 2017

Tiny MCU 3D Renderer Part 2: Dithering

Dithering is an important post processing technique for color quantization, and is especially useful for smoothing gradients with a low precision color space. I got ahead of myself a little bit on the 3D renderer development, and decided to research and experiment with various dithering algorithms. The most popular algorithm is arguably Floyd-Steinberg, which is based upon error diffusion. I used this algorithm back in 2009 for an image processing side-project.

It's safe to say I've learned a bit more about dithering in the last 8 years. Most obviously that Floyd-Steinberg is not ideal for animations because error diffusion will cause an avalanche of artifacts over the temporal domain. A noisy animation could be nice - even artistic - if the noise was evenly distributed. Avoiding the grainy look may be a better option, however. To that end, Bayer's ordered dithering algorithm is commonly used. Unfortunately, the apparent pattern may be too distracting. Various deterministic noise functions are also useful (e.g. pink noise or blue noise ... definitely not white noise).

My first dithering attempt was simple: I would draw a smooth gradient from black to white, using only 2 stops: black at 0.0 and white at 1.0. It was immediately clear that I needed some gamma correction, because my gradient was far too bright overall (when compared to a linear gradient without dithering). Everything I know about gamma, I learned from this article; highly recommended read. This was the first decent dithered gradient I created, using 2 stops:
You'll have to stand pretty far away from the image, and maybe squint a bit to see how the gradient tones line up (note that gamma correction was performed with γ = 1.8, which looks correct on macOS and Windows 10). Not bad for two shades! Close up though, the pattern is a little too strong. It will look better when applied to an image with lower frequency components; the linear gradient is the same pattern of pixels repeated vertically. If applied to the head model, the dithering would probably look rather nice (TBD). But we can always do better!

Tuesday, August 8, 2017

Tiny MCU 3D Renderer Part 1

It's hard to believe that it has been two years since my last blog update. A lot has happened since then, but nothing to write about. I have done surprisingly little in the way of game development or hobby programming since js13k-2015. I experimented with Rust a bit, kept up on some minor maintenance work for my nodeJS Capstone bindings, and I've played a whole lot of Rocket League.

But today I want to share some progress on something that I have been working on periodically for a very long time, because I've been getting more serious about it recently. In the tradition of keeping up my personal motivation, it's time to start sharing what I've been doing. It's not much to look at, but here it is:

3D Renderer in Rust (100% Software)

This is rendered entirely in software using Rust. And, well, that's about all there is to it! Flat-shaded triangles rendered with orthographic projection. I have other screenshots from earlier stages of development, including a wireframe raster, and polygonal (as above) without depth correction. In this screenshot, I had just added a depth buffer which completes all of the geometry rendering work. Next steps are adding diffuse texture mapping and perspective projection. I'll get to that later.

Sunday, September 13, 2015

It's a Lovely Day for a Postmortem

After Liberated Pixel Cup, I promised myself I would never again enter a month-long game jam competition. It was just too exhausting. And then I discovered js13k. I guess I can't refuse a challenge. I also noticed the numerology around the number 13. I dig it! That's my number. To make matters even better, the competition deadline fell on my birthday (today).

What Is It?

The theme word announced for js13k this year was "reversed". That provoked many immediate ideas, the most enticing of which was a driving game where ... you guessed it! You drive in reverse. I envisioned a game like Outrun, Rad Racer, or Road Rash. A road vanishing in the distance, and all you can do is drive away from it. Absurd.

Soon enough, the Scope Creep Monster came knocking. I suddenly had a fully 3D rendered world, with trees, and rocks, and billboards, and mountains. Other cars on the road to avoid, and cops that chase you with sirens blaring (because hey, you're causing moral outrage through reckless driving).

The cutback finally came just a few days into the project. I decided to take inspiration from Desert Bus, known for 8 hours of driving on a perfectly straight road in an empty desert with literally nothing exciting happening ever. That's the game I wanted! The worst game ever made could only be made worse by driving backwards. This is its story.

First Steps

My first task was to find a way to get a full 3D game crammed into 13KB. This is no easy challenge, mind you. The most popular 3D framework is probably Three.js, and it clocks in at over 400KB minified! Another popular framework, Babylon.js, is over 800KB... You know what that means. Roll-your-own 3D engine? Pretty much! I had to use straight-up WebGL without all the fancy doodads provided by a framework. (Note: There are probably minimal 3D frameworks out there, I just don't know of any.)

With my framework chosen (lol), I set out to research some of the tricks used by js1k alumni. This is the same idea, except they get a meager 1,024 bytes to work with. Obviously they have some pretty good tech to do much in a little over a thousand bytes! (The first three paragraphs in this blog post are about 1KB.) I was able to find some good tips on The Googlie. Many of the tips were obvious, but then there were a lot of truly innovative ones, too! I definitely recommend checking out some of the previous js1k entries, even if just for inspiration!

My first commit had a blue triangle rotating and scaling on a white background. Super exciting! Important note: this is my first attempt at making a 3D game. I know the theory, let's put it to the test.

Art, Music, and Maps

When I said many of the tips were "obvious", I was really referring to procedural content generation. You're not going to squeeze a large map into such a tiny space, but you can randomly generate a map that goes on for infinity with just a small piece of code! And you can go deeper; generate all of your art, music, and sound effects procedurally, too!

So, a few lines of code can generate textures and music, huh? An excellent paper from 2006 explains in detail: Procedural Content Generation by Bjarki Guðlaugsson. This is the original source of my own personal connection with PCG; a paper which I read back then eagerly seeking information after the release of the 96KB FPS, .kkreiger.

The true first step, then, is to choose a PCG algorithm. For simplicity, I decided I would only use one, with a generator pattern if I needed it to create different kinds of content. There are numerous algorithms to pick from. The first that came to mind was Perlin Noise, of which I am familiar. The thing is, everyone's using Perlin Noise, since Minecraft exploded its popularity. (Nothing wrong with that, and the noise function is fully capable of doing a lot more than create Minecraft clones.)

I wanted to try something new. What I found was the diamond-square algorithm. What convinced me about this was the happy "starry sky and mountain" image about 1/3 down the page. Followed up by a cloud. Perfect, it's exactly what I needed!

After a few false starts, I had the diamond-square working in JavaScript. Right away, I had a solid-colored mountain rendered from a single row of my 2D height map. Then I added all of the rows as individual layers, each with a slightly darker color. For added "coolness", I used the same height map to render clouds.

From there, a few adjustments were made to the layer positioning and interpolation within the cloud. Crucially, the 2D height map also grew from 128x128 to 512x512 (which was deemed capable of reasonable quality, but incapable of reasonable speed). This is what I ended up with, still just rendering directly to a single texture (e.g. not usable for animations).

Important note: I've never used procedural content generation in a game. I know the theory, let's put it to the test.


Porting that texture renderer to WebGL was a pain. Ideally, I would have generated 3D geometry and used the fragment shader to add haze at runtime. But I wanted an old-school look. Remember, Rad Racer, not Need For Speed! So I settled on 8 layers, each drawn with 16 rows of the height map.

It also didn't help that I had a bug in my vertex shader. It took two days to determine the cause of the unusual rendering of my 3D geometry. It was simple: place a textured quad in 3D space at "some appropriate scale", then place another quad in front of it, scaled less, etc. Until all layers where in place. The issue I had was finding out what "the proper scale" was for each layer. From testing, it appeared to be on a logarithmic scale; for each unit of distance back, the layer size had to double to get decent results. It was truly mind boggling.

After fighting with the geometry and triple-checking my perspective matrix, I broke down and compared my code against a perspective demo provided by Gregg Tavares. Perspective matrix computation was spot-on. Then it hit me; vertex shader! Comparing the two, I noticed the only real difference is that I was multiplying the position vector by the matrix. You're doing it wrong.

With the geometry fixed, I went on to add colors to my vertex attributes (for linear gradients). The gradients evolved into a sunset, which demanded a new color scheme.

This was my first attempt at picking the right color scheme. It's pretty close to the final choice. After that, I added four layers of clouds, each with their own random color level with distinct spectrums; orange, blue, purple, peach. This is what gives it that "Arizona sunset" look. Seeing it in motion is strikingly realistic.

w00t! Background is done. All that's left is something to drive on...

The Road Ahead

As a dumb test, I created three triangles and laid them out in my 3D coordinate space. Looks like a perspective road to me!

The trouble here is the vanishing point goes into infinity. To simulate this with a rectangular road would have been infeasible; the road is always going to hit the back of my perspective frustum before it gets to 1px wide. Not to mention the road needs to curve, and will make it too wonky to fake or force the perspective. The solution then is to fade the road into the mountain background using those linear gradients that I love so much.

Shown in this screenshot is bad premultiplied alpha blending, which was fixed afterward. :) It still demonstrates the technique well enough. The perspective looks quite different as well, because the road is now made with a rectangle laying down on the surface, instead of a triangle.

Also notice the difference in the clouds. No code changes. Just regenerated with different random values. Pretty striking!

Now about that dull road ...

The Road Behind

I had to mull over the challenge of constructing curved roads for a few days. After all, at this point I only had a single, gray rectangle. I would have to chop it into smaller rectangles, and then somehow squeeze and stretch them in the right way to get a realistic winding road.

Back to the fractals! I already had a pluggable noise generator, since my diamond-square implementation was built with it in mind. I did some research on pink noise and experimented with the algorithm presented on that site. I found that it looked too much like white noise for my tastes. By limiting the range of motion for a random walk of white noise, I could generate much more suitable pink-ish noise with the diamond-square.

I plugged in a visualization of the fractal data (red), and drew a "road" (black) by rotating line segments by a fraction of the fractal data on every step.

And another one for comparison.

Not bad! However, I did find out later that the algorithm which drew these "roads" was not pivoting along the line segment as it was supposed to, but pivoting at its origin in the upper center of the image. That's why the roads seem very smooth at first, and then get more chaotic toward the end, where the small rotations have a greater effect on the more distant segments.

Now I have a road paving algorithm, this is going to be awesome!

Extending the 1D Road to 2D

My road is so far still single-dimensional; it's just a line. I have to extend it to 2D by giving it arbitrary width. Doing this required a plan. For every segment, I would extend perpendicular (to the paving direction) by half of the width in each direction. These two points would be recorded. Then the segment would be rotated, and walk one unit to pave the segment. This process would be repeated, each time creating a rectangle (quad) from the two new points and the two last points, building a road around my simple 1D curvy line.

This is what I saw in my head as I designed the road 2D paving algorithm. In step 1, the red dot is the current location, and the two blue dots are the "next points" to compute. This is a straight segment.

In step 2, the current location is rotated, walked one unit, and then it's just a straight shot out to the sides to hit the blue points, which are what I want to capture.

The 3rd step shows the current location (red dot) advanced, and the extraneous geometry removed, leaving two triangles (a single quad).

The algorithm repeats like this forever, building an infinite road that is anti-dull. With this idea in place, I updated my visualization to draw 2D roads.


Extending the 2D Road to 3D

This was so easy, it almost doesn't deserve an entire section of this postmortem. But I'm gonna, because I have another screenshot to show!

The whole process of the 3D extension was to use the X-Z plane. Ta da! While hills were definitely a part of my original Scope Creep Monster plan, there was no way that would have been a realistic goal. So the road never diverges from -1 on the Y axis (which is below the camera at Y:0).

Here is the first 3D road that I was able to render. Notice the black-and-white pattern, clearly showing the individual quad segments, and a small piece of the 2D visualization of which it represents in 3D.

I still didn't have a texture for it, but even dull gray would be better than a piano road.

Very nice! I can now generate a road infinitely. My fractal is 128x128, so if I compute segment angles for each point in the fractal, that gives me 16,384 segments of road before it cycles. Each segment is 1 unit deep, or about 1 meter in human length. 16 km of random road for free!

To keep memory usage sane for the road, only 28 segments are kept at a time. (28 happens to be evenly divisible by 4; the number of segments of depth for my asphalt texture, and also happens to be the depth at which the first layer of mountains appears.) When a new segment needs to be created, all segments are shifted up (into the distance) and the farthest segment gets pushed off into the void. Because the road is cyclical, the texture coordinates from the dropped segment are reused by the new segment. (This will become important later on.)

Of course, I'm still very far from being done, by this point. I'm already 3 weeks into the competition, and I don't even have any interactive elements. So far it's all been hand-wavy "realistic graphics are so important!" stuff. That was my biggest mistake of this project. (Don't get me wrong, it's a great tech demo.) Time to work on game play elements, right?


Gouraud shaded roads do not belong with that sunset! We need an asphalt texture. Yes, Leo, yes.

I looked at a lot of photos of asphalt on The Googlie Images. (Try telling that to your girlfriend...) Seems like it should be pretty easy to generate a texture... Just a bunch of white noise made really dark! But white noise doesn't actually look like asphalt, it looks like TV static. And darkening TV static just looks like dark TV static. No, we need a method. Something more natural. Something that looks bumpy, instead of noisy.

In my search, I came across this Gimp tutorial: http://gimpchat.com/viewtopic.php?f=23&t=9760 It isn't super great, but it would do. I have the directions, now I need to codify it. I already have clouds, and white noise is a good replacement for HSV noise. The steps I'm missing are "sparkle", "emboss", and "gaussian blur". (I skipped making any cracks.) Blur is an easy one; just a matter of duplicating neighboring pixels with some falloff. I was able to combine sparkle and emboss into a single approximation by applying another "neighboring pixel" algorithm after the blur step; if the neighboring pixels are too dark, make this pixel bright. Throw in some desaturation and...

That'll do! Bonus: this texture wraps appropriately, which is important for realism (there I go again!)

Now it looks [a little bit] like freshly paved asphalt. It's missing something, though. Oh yeah, lines for the driving lanes. This was a fun bit! I created something like a paint roller simulation to make sure the deep crevasses in the asphalt left air bubbles that would pop before the paint dries.

I kid, I kid. The intension, of course, was for the texture to look like the paint had imperfections. That's what makes the game's unique style so "realistic"; I relished in the imperfections! The algorithm is simple; if the color is too dark, leave it dark. If its brightness is above a certain threshold, replace it with a yellow or white pixel. Plus some white noise for added roughness.

Two interesting points: First, the vertical lines do not have a perfectly flat edge (again, by design). There is an extra condition along with the brightness test; on the edges of the lines, the brightness threshold is raised, meaning fewer pixels will be colored. Second, the texture shown here is what appears in the final build, even though two other line patterns are generated (double solid, and broken left). This one creates the broken right line.

My intention was to randomly choose one of the three textures for a random run of highway. It's complicated a bit by my road paving algorithm, which is inherently iterative. The idea was to take the value in the first column of the fractal on the current row, and derive two numbers: which line pattern to use [0..2] and how long to let it run. That would have been deterministic.

The harder part, IMHO, would be putting the proper texture coordinates into the geometry buffer as it shifts. Remember when I said that the texture coordinate reuse would be important? This is where it bites us. With additional textures on the road, my buffer is no longer cyclical, making the shift operation hard. Not impossible, just "I don't have time to do this right now."

A selection of screenshots showing the different line patterns. Now I have a road that is drawn correctly. 2 days left in the competition, and I still need to make the camera move along the road, and add some kind of interactivity. Jeez!


Linear interpolation (LERP, aka tween) is a glorious thing. You've seen it before. You've probably even used it. It creates smooth (linear) transitions between two states over time. To create the driving animation between plays, I run a LERP between each road segment, along the midline. It interpolates the camera position and rotation in one step. Finally, the camera is translated to the right side of the road, about where a driver would be sitting (if you're in the US).

The LERP was a bit of a problem to get right. Mostly because camera matrices are awful. I ended up with a decent matrix inversion function based on maths from an awesome website I found. It's slightly cheaper (and easier to understand) than the popular method.

Anyway, I finally got something to work "good enough", and that's what you see in the final build. It's a little bit bouncy when the camera jumps to the next segment. I haven't looked into any way to make that better.

1.5 days remain, and I still don't have any interactive elements to the game! My pacing on this was atrocious.

Input Output

Scope Creep Monster was getting a little unruly, to be quite honest. I still wanted it all; desktop support, mobile support, keyboard input, gamepad input, motion controls, ... I must be insane.

Sure! Why not? It's not like it's a whole lot of code! In an evening, I had a full featured input module that covered keyboard, gamepad, and motion controls. Each input sets normalized state in an input object, which is used later by the game.

I plugged my new input object into the camera code, which required a lot of refactoring, actually. But it worked! With a little bit of physics code, I was able to drive in reverse! Of course, the first iteration was horribly broken. The auto-driving camera was responsible for shifting the road segments, but with a human in control, I cannot use the same LERP! Humans don't drive linearly.

What I needed was collision detection; determine when the camera crossed the "current location" of the road generator, and generate the next segment! The road would be generated as it was driven on. (You can see the effect of this in the final build by making a really sharp turn... There's nothing but the void behind you!) I needed collision detection anyway to keep the player on the road. Any off-roading could not be allowed.

I could have used any number of collision algorithms, like SAT. But I felt that was unnecessary overkill, there had to be a cheaper way! In a quick flash of inspiration, I decided to try a triangulation between the camera and the two points on either side of the road. (Remember the image earlier with the red dot and two blue dots? Yes those blue dots.) This turned out to be really easy! Not even a triangulation, really. Just two dot-products.

I have no idea what a dot-product is (it's a 1D projection of one vector onto another), but if you take the dot product of a vector against itself, you get the square of the vector's length! It's basically the pythagorean theorem, so yeah, I guess it is triangulation, of sorts! Anyway, the camera's position minus the point's position is the vector whose length I want. The variables are as follows:

  • The road is 6 units wide
  • The camera is somewhere within the area covered by the last [generated] segment of the road.
  • The camera can only move backwards

Given these constraints, it's easy to compute when the player passes between the two points: take the square root of each vector, and add them. If the sum is near 6 (the width of the road) then the line between the two points is being crossed. Try it out on a sheet of graph paper! It's simple geometry. For simplicity, I consider "near 6" to be < 6.1. That gives a 10% margin of error, more than enough to account for weird floating point precision and rounding errors.

That takes care of generating more road. Determining whether the player left the road was equally easy! The road is 6 units across, so logically, if either point is ever more than 6 units away from the camera, the player has left the road. This can be simplified a bit because you don't need a square root of the dot-product; just compare the dot-product directly to 6².

Magic! I have a complete game, with a full day to spare. What could possibly go wrong?

Sound Makes It FUN

This is a tip I learned long, long ago; music and sound effects are the real key to creating an enjoyable experience. This is part of the "juicing" philosophy to game development. You can have the craziest screen shake, most intense particle effects, and super colorful warpy shader things... But without sound effects to go with it, it's kind of dead. While my game has none of those juicy things, I certainly didn't go crazy on sounds, either!

I woke up on "launch day", with a full 16-and-something hours until deadline. The first thing on my TODO list was music. Earlier I had played with the idea of fully procedural music generation, so I did some studying, and now have a cursory understanding of the math behind music theory. There's not much to it, but I don't have enough practical knowledge to make use of any of that. My attempt with the WebAudio API was the ultimate disaster. Thankfully, that never made it into a single commit.

I was then informed on The Twitters by a fellow js13k developer, "Sonant-x to the rescue!" Holy crap, Ryan, you saved the day! Within an hour or two, I had my sound track. It turned out well. So well in fact, that I've had the music playing on repeat almost constantly since I wrapped it up. How in the hell? I'm no musician. Did that really come from my brain? Props to Nicolas Vanhoren, Marcus Geelnard, and Jake Taylor for their work which culminated into a tool that allows a tool like me to create a melody so peaceful and serene.

You're gonna need it, because this game ... Oh, this game.

The music really brought the project to fruition, IMO. But with over half a day remaining, there was plenty of time to juice it up and make the experience a little more coherent. I added a title screen by reusing the LERP animation (auto-driving) and putting "cursive" font-family text (a div element) over the canvas. I re-reused the animation for the loss screen, and made the loss text as happy as I could. Because let's face it, the game is truly brutal and unforgiving. Every little bit of happiness that can be impressed upon my unfortunate audience will be well-deserved.

Oh yeah, and iOS is a constant source of grief! I had to add a "Tap to continue" message after the loader for iOS, because SCREW YOU APPLE. That's why. iOS silences all audio until audio is played in response to a user interaction. I don't know why. I pinched a small function from howler.js to enable audio on iOS in response to a tap. The tap only enables audio about 10% of the time on the iOS simulator. It seems a bit better on real hardware. Oh well, I give up. Chrome for Android works flawlessly without this terrible hack.

Sound effects! I was still missing sound effects. There's only one sound effect that a driving game truly needs. A motor! I knew from my previous music research that synthesis was the way to go. But I stopped short of understanding Fourier Transforms, so I couldn't really get into it that much. Instead, The Googlie showed me the light! A tiny javascript library that generates motor sounds! With a bit of tuning, it would be perfect.

First, the library as-is only generated audio for the left channel in a stereo audio buffer. Easy enough to duplicate the wave into both channels. And second, it only generated purely random (white noise) sounds. I wanted more control over it, so I added a simple deterministic generator that produced a fine motor sound. It just had to be hooked up to my physics (completed earlier in the day, following input). Velocity affects both motor volume and frequency, which is pretty darned convincing.

Strangely, the motor sound is kind of awful on Chrome for Android. I haven't looked into why that is.

Final Touches

There isn't much more to say about the development process. I added a score counter which tracks the distance driven, and saves the high score to localStorage. Nothing special there! Another fix added late was support for 3:1 screen ratios (crazy), because the cloud layers are capable of scrolling all the way until a gap appears at the right side on wider display ratios. This was fixed by stretching the clouds horizontally a little bit.

And crucially, a game breaking bug was fixed just before submission; it only occurred in the minified/compressed build, due to overaggressive compression techniques! At just under 9KB (with 4KB to spare, that's about 30%) I could really afford to loosen up on the compression. I removed the breaking code, which cost 70 bytes (lol) but increased compatibility. All good!

What Went Wrong

iOS was painful almost the entire way. First, I was surprised an early build worked at all on my ancient iPhone 4S. Little did I know that adding an awesome hack would completely break it on iOS. I demand iOS compatibility! So I removed the hack very late to get it working acceptably again. And the final punch to my gut from iOS is the terrible motion controls. I didn't bother adding a manual calibration step (which was honestly a mistake). The gyro is not the most accurate thing in the world. It kind of sucks, actually.

The other thing I'm disappointed with is spending 90% of my time on graphics. A fatal rookie mistake if ever there was one. I don't know if I'll ever learn to mitigate this issue properly.

What Went Right

Uh, well, yeah. It's safe to say that pretty much everything (except iOS) went very well! There were normal development hiccups and bugs along the way (par for the course), but looking back, I don't think I've ever had a project that I've been more proud of.

There were a lot of personal firsts, here! First 3D game, first game using Procedural Content Generation, first to use WebAudio, WebGL, Gamepad, and DeviceOrientation APIs... To say that I did poorly with any of these things is missing the point! You gotta start somewhere, and for a game like Lovely Drive to set the bar high for myself right off the bat, in so many areas... Well, that's really quite humbling. (To myself, anyway.)

I feel like I also hit my Desert Bus homage goal (after cutting out the Scope Creep Monster). You can drive forever in this game, backwards of course. Importantly, you can take your time, or blaze a trail recklessly. There's no time limit, there are no obstacles to overcomplicate the already-cramped highway. The presentation is one of serenity and tranquility. I've had the music on loop almost non-stop, not out of hubris or ego. But because it truly instills an emotional reaction when I listen to it. Especially with a beautiful, inviting (ceremonial, even) font overlaid on a never ending desert sunset. It's probably the most gorgeous thing I will ever make.

I didn't have any trouble with the file size. The only reason I almost hit 9KB before release was because I had to add a bunch of one-off code (the devil, to any size-restricted project). I can thank math for that.

Closing Thoughts

The game is not the most fun to play. It is challenging, and perhaps could have an audience in the party game crowd (see who can get the farthest distance in the shortest time?) But really it is not a casual game by any stretch. It is Desert Bus in reverse. That sums it up nicely.

The font is different between Desktop and Mobile. I didn't do that; browser vendors did.