Sunday, January 31, 2016

Hot Reloadable JavaScript, Batman!

JavaScript is my new favorite prototyping language. Not because the language itself is fantastic. I mean, it's not too bad. It actually has a lot of similarity to Lua, but it's hidden under a heavy layer of WAT!?, like:

  • Browser incompatibilities!?
  • Semi-colons are optional, but you "should" put them there anyway!?
  • Propagation of null, undefined and NaN until they cause an error very far from where they originated!?
  • Weird type conversions!? "0" == false!?
  • Every function is also an object constructor!? x = new add(5,7)!?
  • Every function is also a method!?
  • You must check everything with hasOwnProperty() when iterating over objects!?

But since Lua is a work of genius and beauty, being a half-assed version of Lua is still pretty good. You could do worse, as languages go.

And JavaScript is actually getting better. Browser compatibility is improving, automatic updates is a big factor in this. And if your goal is just to prototype and play, as opposed to building robust web applications, you can just pick your favorite browser, go with that and don't worry about compatibility. The ES6 standard also adds a lot of nice little improvements, like let, const, class, lexically scoped this (for arrow functions), etc.

But more than the language, the nice thing about JavaScript is that comes with a lot of the things you need to do interesting stuff -- a user interface, 2D and 3D drawing, a debugger, a console REPL, etc. And it's ubiquitous -- everybody has a web browser. If you do something interesting and want to show it to someone else, it is as easy as sending a link.

OK, so it doesn't have file system access (unless you run it through node.js), but who cares? What's so fun about reading and writing files anyway? The 60's called, they want their programming textbooks back!

I mean in JavaScript I can quickly whip up a little demo scene, add some UI controls and then share it with a friend. That's more exciting. I'm sure someone will tell me that I can do that in Ruby too. I'm sure I could, if I found the right gems to install, picked what UI library I wanted to use and learned how to use that, found some suitable bundling tools that could package it up in an executable, preferably cross-platform. But I would probably run into some annoying and confusing error along the way and just give up.

With increasing age I have less and less patience for the sysadmin part of programming. Installing libraries. Making sure that the versions work together. Converting a script to something that works with our build system. Solving PATH conflicts between multiple installed cygwin and mingw based toolchains. Learning the intricacies of some weird framework that will be gone in 18 months anyway. There is enough of that stuff that I have to deal with, just to do my job. I don't need any more. When I can avoid it, I do.

One thing I've noticed since I started to prototype in JavaScript is that since drawing and UI work is so simple to do, I've started to use programming for things that I previously would have done in other ways. For example, I no longer do graphs like this in a drawing program:

Instead I write a little piece of JavaScript code that draws the graph on an HTML canvas (code here: pipeline.js).

JavaScript canvas drawing cannot only replace traditional drawing programs, but also Visio (for process diagrams), Excel (graphs and charts), Photoshop and Graphviz. And it can do more advanced forms of visualization and styling, that are not possible in any of these programs.

For simple graphs, you could ask if this really saves any time in the long run, as compared to using a regular drawing program. My answer is: I don't know and I don't care. I think it is more important to do something interesting and fun with time than to save it. And for me, using drawing programs stopped being fun some time around when ClarisWorks was discontinued. If you ask me, so called "productivity software" has just become less and less productive since then. These days, I can't open a Word document without feeling my pulse racing. You can't even print the damned things without clicking through a security warning. Software PTSD. Programmers, we should be ashamed of ourselves. Thank god for Markdown.

Another thing I've stopped using is slide show software. That was never any fun either. Keynote was at least tolerable, which is more than you can say about Powerpoint. Now I just use Remark.js instead and write my slides directly in HTML. I'm much happier and I've lost 10 pounds! Thank you, JavaScript!

But I think for my next slide deck, I'll write it directly in JavaScript instead of using Remark. That's more fun! Frameworks? I don't need no stinking frameworks! Then I can also finally solve the issue of auto-adapting between 16:9 and 4:3 so I don't have to letterbox my entire presentation when someone wants me to run it on a 1995 projector. Seriously, people!

This is not the connector you are looking for!

And I can put HTML 5 videos directly in my presentation, so I don't have to shut down my slide deck to open a video in a separate program. Have you noticed that this is something that almost every speaker does at big conferences? Because apparently they haven't succeeded in getting their million dollar presentation software to reliably present a video file! Software! Everything is broken!

Anyhoo... to get back off topic, one thing that surprised me a bit about JavaScript is that there doesn't seem to be a lot of interest in hot-reloading workflows. Online there is JSBin, which is great, but not really practical for writing bigger things. If you start googling for something you can use offline, with your own favorite text editor, you don't find that much. This is a bit surprising, since JavaScript is a dynamic language -- hot reloading should be a hot topic.

There are some node modules that can do this, like budo. But I'd like something that is small and hackable, that works instantly and doesn't require installing a bunch of frameworks. By now, you know how I feel about that.

After some experimentation I found that adding a script node dynamically to the DOM will cause the script to be evaluated. What is a bit surprising is that you can remove the script node immediately afterwards and everything will still work. The code will still run and update the JavaScript environment. Again, since this is only for my personal use I've not tested it on Internet Explorer 3.0, only on the browsers I play with on a daily basis, Safari and Chrome Canary.

What this means is that we can write a require function for JavaScript like this:

function require(s)
    var script = document.createElement("script");
    script.src = s + "?" +;
    script.type = "text/javascript";
    var head = document.getElementsByTagName("head")[0];

We can use this to load script files, which is kind of nice. It means we don't need a lot of <script> tags in the HTML file. We can just put one there for our main script, index.js, and then require in the other scripts we need from there.

Also note the deftly use of + "?" + to prevent the browser from caching the script files. That becomes important when we want to reload them.

Since for dynamic languuages, reloading a script is the same thing as running it, we can get automatic reloads by just calling require on our own script from a timer:

function reload()

if (!window.has_reload) {
    window.has_reload = true;
    window.setInterval(reload, 250);

This reloads the script every 250 ms.

I use the has_reload flag on the window to ensure that I set the reload timer only the first time the file is run. Otherwise we would create more and more reload timers with every reload which in turn would cause even more reloads. If I had enough power in my laptop the resulting chain reaction would vaporize the universe in under three minutes. Sadly, since I don't all that will happen is that my fans will spin up a bit. Damnit, I need more power!

After each reload() I call my render() function to recreate the DOM, redraw the canvas, etc with the new code. That function might look something like this:

function render()
    var body = document.getElementsByTagName("body")[0];
    while (body.hasChildNodes()) {

    var canvas = document.createElement("canvas");
    canvas.width = 650;
    canvas.height = 530;
    var ctx = canvas.getContext("2d");

Note that I start by removing all the DOM elements under <body>. Otherwise each reload would create more and more content. That's still linear growth, so it is better than the exponential chain reaction you can get from the reload timer. But linear growth of the DOM is still pretty bad.

You might think that reloading all the scripts and redrawing the DOM every 250 ms would create a horrible flickering display. But so far, for my little play projects, everything works smoothly in both Safari and Chrome. Glad to see that they are double buffering properly.

If you do run into problems with flickering you could try using the Virtual DOM method that is so popular with JavaScript UI frameworks these days. But try it without that first and see if you really need it, because ugh frameworks, amirite?

Obviously it would be better to reload only when the files actually change and not every 250 ms. But to do that you would need to do something like adding a file system watcher connected to a web socket that could send a message when a reload was needed. Things would start to get complicated, and I like it simple. So far, this works well enough for my purposes.

As a middle ground you could have a small bootstrap script for doing the reload:

window.version = 23;
if (window.version != window.last_version) {
    window.last_version = window.version;

You would reload this small bootstrap script every 250 ms. But it would only trigger a reload of the other scripts and a re-render when you change the version number. This avoids the reload spamming, but it also removes the immediate feedback loop -- change something and see the effect immediately which I think is really important.

As always with script reloads, you must be a bit careful with how you write your scripts to ensure thy work nicely with the reload feature. For example, if you write:

class Rect

It works well in Safari, but Chrome Canary complains on the second reload that you are redefining a class. You can get around that by instead writing:

var Rect = class {

Now Chrome doesn't complain anymore, because obviously you are allowed to change the content of a variable.

To preserve state across reloads, I just put the all the state in a global variable on the window:

window.state = window.state || {}

The first time this is run, we get an empty state object, but on future reloads we keep the old state. The render() function uses the state to determine what to draw. For example, for a slide deck I would put the current slide number in the state, so that we stay on the same page after a reload.

Here is a GIF of the hot reloading in action. Note that the browser view changes as soon as I save the file in Atom:

(No psychoactive substances where consumed during the production of this blog post. Except caffeine. Maybe I should stop drinking coffee?)

Friday, January 29, 2016

Stingray Support -- Hello, I Am Someone Who Can Help

Hello, I am someone who can help. 

Here at the Autodesk Games team, we pride ourselves on supporting users of the Stingray game engine in the best ways possible – so to start, let’s cover where you can find information!

General Information Here!

Games Solutions Learning Channel on YouTube:
This is a series of videos about Stingray by the Autodesk Learning Team. They'll be updating the playlist with new videos over time. They're pretty responsive to community requests on the videos, so feel free to log in and comment if there's something specific you'd like to see.
Check out the playlist on YouTube.

Autodesk Stingray Quick Start Series, with Josh from Digital Tutors:
We enlisted the help from Digital Tutors to set up a video series that runs through the major sections of Stingray so you can get up and running quickly.
Check out the playlist on YouTube.

Autodesk Make Games learning site:
This is a site that we've made for people who are brand new to making games. If you've never made a game before, or never touched complex 3D tools or a game engine, this is a good place to start. We run you through Concept Art and Design phases, 3D content creation, and then using a game engine. We've also made a bunch of assets available to help brand new game makers get started.

Creative Market:
The Creative Market is a storefront where game makers can buy or sell 3D content. We've got a page set up just for Stingray, and it includes some free assets to help new game makers get started.

Stingray Online Help
Here you'll find more getting started movies, how-to topics, and references for the scripting and visual programming interfaces. We're working hard to get you all the info you need, and we're really excited to hear your feedback.

Forum Support Tutorial Channel on YouTube:
This is a series of videos that answers recurring forums questions by the Autodesk Support Team. They'll be updating the playlist with new videos over time. They're pretty responsive to community requests on the videos, so feel free to log in and comment if there's something specific you'd like to see.
Check out the playlist on YouTube.

You should also visit the Stingray Public Forums here, as there is a growing wealth of information and knowledge to search from.

Let's Get Started

Let’s get started. Hi, I’m Dan, nice to meet you. I am super happy to help you with any of your Stingray problems, issues, needs or general questions! However, I’m going to need to ask you to HELP ME, HELP YOU!!

It’s not always apparent when a user asks for help just exactly what that user is asking for. That being the case, here is some useful information on how to ask for help and what to provide us so that we can help you better and more quickly!
  •  Make sure you are very clear on what your specific problem is and describe it as best you can.
    • Include pictures or screen shots you may have
  • Tell us how you came to have this problem         
    • Give us detailed reproduction steps on how to arrive at the issue you are seeing
  • Attach your log files!
    • They can be found here: C:\Users\”USERNAME”\AppData\Local\Autodesk\Stingray\Logs
  • Attach any file that is a specific problem (zip it so it attaches to forum post)
  •  Make sure to let us know your system specifications 
  •  Make sure to let us know what Stingray engine version you are using

On another note … traduire, traduzir, 翻, Übersetzen, þýða, переведите, ਅਨੁਵਾਦ, , and ... translate! We use English as our main support language, however, these days – is really, really good! If English is not your first language, please feel free to write your questions and issues in your native language and we will translate it and get back to you. I often find that it is easier to understand from a translation and this helps us get you help just that much more quickly!

In Conclusion

So just to recap, make sure you are ready when you come to ask us a question! Have your issue sorted out, how to reproduce it, what engine version you are running, your system specs and attach your log files. This will help us, help you, just that much faster and we can get you on your way to making super awesome content in the Stingray game engine. Thanks!

Dan Matlack
Product Support Specialist – Games Solutions
Autodesk, Inc.

Wednesday, January 20, 2016

Introducing the Stingray Package Manager (spm)

The Stingray Package Manager, or spm, is a small Ruby program that is responsible for downloading specific versions of the external artifacts (libraries, sample projects, etc) that are needed to build the Stingray engine and tools. It's a small but important piece of what makes one-button builds possible.

By one-button builds I mean that it should be possible to build Stingray with a single console command and no human intervention. It should work for any version in the code history. It should build all tools, plugins and utilities that are part of the project (as well as meaningful subsets of those for faster builds). In addition, it should work for all target platforms, build configurations (debug, development, release) and options (enabling/disabling Steam, Oculus, AVX, etc).

Before you have experienced one-button builds it's easy to think: So what? What's the big deal? I can download a few libraries manually, change some environment variables when needed, open a few Visual Studio projects and build them. Sure, it is a little bit of work every now and then, but not too bad.

In fact, there are big advantages to having a one-button build system in place:

  • New developers and anyone else interested in the code can dive right in and don't have to spend days trying to figure out how to compile the damned thing.

  • Build farms don't need as much baby sitting (of course build farms always need some baby sitting).

  • All developers build the engine in the same way, the results are repeatable and you don't get bugs from people building against the wrong libraries.

  • There is a known way to build any previous version of the engine, so you can fix bugs in old releases, do bisect tests to locate bad commits, etc.

But more than these specific things, having one-button builds also gives you one less thing to worry about. As programmers we are always trying to fit too much stuff into our brains. We should just come to terms with the fact that as a species, we're really not smart enough to be doing this. That is why I think that simplicity is the most important virtue of programming. Any way we can find to reduce cognitive load and context switching will allow us to focus more on the problem at hand.

In addition to spm there are two other important parts of our one-button build system:

  • The cmake configuration files for building the various targets.

  • A front-end ruby script (make.rb) that parses command-line parameters specifying which configuration to build and makes the appropriate calls to spm and cmake.

But let's get back to spm. As I said at the top, the responsibility of spm is to download and install external artifacts that are needed by the build process. There are some things that are important:

  • Exact versions of these artifacts should be specified so that building a specific version of the source (git hash) will always use the same exact artifacts and yield a predictable result.

  • Since some of these libraries are big, hundreds of megabytes, even when zipped (computers are a sadness), it is important not to download more than absolutely necessary for making the current build.

  • For the same reason we also need control over how we cache older versions of the artifacts. We don't want to evict them immediately, because then we have to download hundreds of megabytes every time we switch branch. But we don't want to keep all old versions either, because then we would pretty soon run out of space on small disks.

The last two points are the reason why something like git-lfs doesn't solve this problem out-of-the box and some more sophisticated package management is needed.

spm takes inspiration from popular package managers like npm and gem and offers a similar set of sub commands. spm install to install a package. spm uninstall to uninstall, etc. At it's heart, what spm does is a pretty simple operation:

Upon request, spm downloads a specific artifact version (identified by a hash) from an artifact repository. We support multiple artifact repositories, such as S3, git and Artifactory. The artifact is unzipped and stored in a local library folder where it can be accessed by the build scripts. As specific artifact versions are activated and deactivated we move them in and out of the local artifact cache.

We don't use unique folder names for artifact versions. So the folder name of an artifact (e.g., luajit-2.1.0-windows) doesn't tell us the exact version (y0dqqY640edvzOKu.QEE4Fjcwxc8FmlM). spm keeps track of that in internal data structures.

There are advantages and disadvantages to this approach:

  • We don't have to change the build scripts when we do minor fixes to a library, only the version hash used by spm.
  • We avoid ugly looking hashes in the folder names and don't have to invent our own version numbering scheme, in addition to the official one.
  • We can't see at a glance which specific library versions are installed without asking spm.
  • We can't have two versions of the same library installed simultaneously, since their names could collide, so we can't run parallel builds that use different library versions.
  • If library version names were unique we wouldn't even need the cache folder, we could just keep all the versions in the library folder.

I'm not 100 % sure we have made the right choice, it might be better to enforce unique names. But it is not a huge deal so unless there is a big impetus for change we will stay on the current track.

spm knows which versions of the artifacts to install by reading configuration files that are checked in as part of the source code. These configuration files are simple JSON files with entries like this:

cmake = {
    groups = ["cmake", "common"]
    platforms = ["win64", "win32", "osx", "ios", "android", "ps4", "xb1", "webgl"]
    lib = "cmake-3.4.0-r1"
    version = "CZRgSJOqdzqVXey1IXLcswEuUkDtmwvd"
    source =  {
        type = "s3"
        bucket = "..."
        access-key-id = "..."
        secret-access-key = "..."

This specifies the name of the packet (cmake), the folder name to use for the install (cmake-3.4.0-r1), the version hash and how to retrieve it from the artifact repository (these source parameters can be re-used between different libraries).

To update a library, you simply upload the new version to the repository, modify the version hash and check in the updated configuration file.

The platforms parameter specifies which platforms this library is used on and groups is used to group packages together in meaningful ways that make spm easier to use. For example, there is an engine group that contains all the packages needed to build the engine runtime and a corresponding editor group for building the editor.

So if you want to install all libraries needed to build the engine on Xbox One, you would do:

spm install-group -p xb1 engine

This will install only the libraries needed to build the engine for Xbox One and nothing else. For each library, spm will:

  • If the library is already installed -- do nothing.
  • If the library is in the cache -- move it to the library folder.
  • Otherwise -- download it from the repository.

Downloads are done in parallel, for maximum speed, with a nice command-line based progress report:

The cache is a simple MRU cache that can be pruned either by time (throw away anything I haven't used in a month) or by size (trim the cache down to 10 GB, keeping only the most recently used stuff).

Of course, you usually never have even have to worry about calling spm directly, because make.rb will automatically call it for you with the right arguments, based on the build parameters you have specified to make.rb. It all happens behind the scene.

Even the cmake binary itself is installed by the spm system, so the build is able to bootstrap itself to some extent. Unfortunately, the bootstrap process is not 100 % complete -- there are still some things that you need to do manually before you can start using the one-button builds:

  • Install Ruby (for running spm.rb and make.rb).
  • Specify the location of your library folder (with an SR_LIB_DIR environment variable).
  • Install a suitable version of Visual Studio and/or XCode.
  • Install the platform specific SDKs and toolchains for the platforms you want to target.

I would like to get rid of all of this and have a zero-configuration bootstrap procedure. You sync the repository, give one command and bam -- you have everything you need.

But some of these things are a bit tricky. Without Ruby we need something else for the initial step that at least is capable of downloading and installing Ruby. We can't put restricted software in public repositories and it might be considered hostile to automatically run installers on the users' behalf. Also, some platform SDKs need to be installed globally and don't offer any way of switching quickly between different SDK versions, thwarting any attempt to support quick branch switching.

But we will continue to whittle away at these issues, taking the simplifications where we can find them.