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Show HN: Ejecta, A Fast, Open Source JavaScript, Canvas Implementation for iOS (impactjs.com)
190 points by phoboslab on Sept 25, 2012 | hide | past | web | favorite | 45 comments

Thanks for the great response so far!

I also wrote about some implementation details of the Canvas API and the challenges with OpenGL in my blog:


Thanks very much for open sourcing this. Keep up the good work - everything you post is great... great information, and great code. Thanks again!

Have you seen Plask? (http://www.plask.org/) What are your thoughts on it? I guess it doesn't target OpenGL, but I imagine it's pretty fast already...

I purchased ImpactJS after picking the "Creating HTML5 Games" book about it. I was really surprised with the quality of the toolkit and how responsive the developer is. I think it was the best investment I made this year and I can't wait to release some games.

I'm very happy with impact. It's well designed and easy to extend. After quite a bit of exploring different frameworks and engines (including writing my own), I think impact is my long term game dev solution.

ImpactJS is a fantastic tool and Ejecta solves a real problem in a smart way. Phobos Lab does awesome work.

This guy is a hacker in the truest sense, I read a blog post over a year ago about him tinkering away on this. It didn't seem he'd take it this far. It's a great achievement and I'm glad he's been insightful enough to keep it free.

I used Impact two years ago on something and I was so impressed with the API simplicity and power (not to mention the fact that it ran very well). This guy does great work.

Dominic is amazing at what he does. ImpactJS is such a powerful but simple tool. I love that every release is NOT bloatware, but carefully thought out feature enhacements.

Any plans on making it usable without XCode? (or a Mac, for that matter.)

Since the users just write javascript code, as long as you give them a way to insert that code into an app, they wouldn't really need to use the XCode build system at all (I know, app store rules would need to be addressed...)

DirectCanvas from appMobi (I work there) is based on iOS impact (and enhanced) - http://www.appmobi.com . No need for a Mac or XCode.

This looks like a great way to build iOS games in HTML5.

If he could to get this to work as an Android project it could be used to build games for OUYA.

I want this in the browser. Throw away the DOM, and let's just have canvas and JS. Skip loading any HTML or CSS. It would be great.

In fact -- why do we even have browsers?

If only there were some popular write-once run-anywhere VM, we could pretty easily get away from this weird document-oriented web thing forever.

Yeah, like Java. :P

That's pretty much exactly what Blossom[1] is; there's no need to write HTML or CSS.

[1] https://github.com/erichocean/blossom

Yeah, but I'm thinking having the current W3C APIs.

That the canvas API is implemented with OpenGL is very impressive. CocoonJS [1] (a similar project for Android, as noted in the comments below) seems to have taken the same approach.

On a completely tangential note, given that the main desktop browsers now sport hardware accelerated canvas implementations, is there a performance difference in 2D graphics rendered with canvas vs. WebGL?

[1] http://ludei.com/tech/cocoonjs

webgl can be much faster because you can draw many primitives with one call. there's a lot of overhead from js down to gl.

Then what is stopping browser vendors from implementing canvas directly in gl directly, making canvas more or less a wrapper?

Canvas is directly implemented in gl (or directx) in most browsers at this point. WebGL is still faster like the poster above says because you as the programmer an can make optimizations that are not possible with the canvas api like drawing many things with one call.


Isn't JS performance going to suffer if it's using a custom build of JSC that can't JIT?

Yes. I wish we could use the JIT – it would make computational heavy stuff way faster. Most games however aren't performance bound by computation, but by drawing. Not having the JIT isn't as bad as it may seem.

Also, JavaScriptCore recently features a new "low level interpreter" – still not as fast as the JIT, but way faster than it was a few month ago: http://wingolog.org/archives/2012/06/27/inside-javascriptcor...

Native iOS doesn't have JIT

The browser certainly does. Or is this only an alternative to a WebView in an app store app?

even google wasn't able to include a JIT in Chrome for iOS

Safari uses a JIT. Other browsers and UIWebView based applications are not allowed to access the JIT, apparently because it is a security risk. Even lua based apps are not allowed to run luajit because code generation on iOS isn't allowed within apps.

There's even a massive JIT vulnerability in webkit on iOS at the moment.

Interesting! I created Node-Five with a similar goal in mind (low-level graphics and audio from the HTML5 spec):


Glad to see someone had the same idea for iOS :)

Pretty cool.

What about the support for Android, any plans for that?

This project is very much iOS specific. It's written in Objective-C and uses JavaScriptCore (Apple's JS engine). So porting this over to Android would be a lot of work.

But have a look at CocoonJS; it's cross platform (but closed source): http://ludei.com/tech/cocoonjs

I was curious about that too. With android support, it would be a good alternative to Corona (use js instead of Lua).

For iOS, an added benefit of is that JavascriptCore uses Nitro, unlike UIWebView.

JSC as used by an app store app does not use Nitro. As the post stated, JSC is a private framework and the only way to use it in an approved app is to import the source into your project and build a copy of JSC that is bundled with your app. Since the JSC that you use is contained within your executable, iOS doesn't allow the write and execute permissions in memory that would be necessary for JIT.

Reminds me of CocoonJS (basically the same idea, also support for Android but closed source).


Neat in any case. Looks like a nice implementation.

Really great work! One question belonging to this, do you know how to used 4x5 ColorTransform Matrices with JavaScript and WebGL/OpenGL? I can't find anything about this on the I-net.

As far as I am aware, ImpactJS is unfortunately only for tile-based game development on canvas. Has this influenced/limited Ejecta in any way?

Cool. This sounds a bit like Game Closure (http://gameclosure.com/)

The quicker you guys realize it the better, Flash is the better choice.

Apple needs to just buy you out right and include this in safari.

Just wanted to tell this is some really cool work you've done.

Any actual benchmarks?

I haven't done any formal benchmarks. A quick test with 1000 sprites runs with 60fps on the iPhone4s.

Also try loading this in Mobile Safari and compare it to the video: http://www.phoboslab.org/crap/bezier/

Bugger. There goes my pet project. Nice one phoboslab!

The word "Ejecta" sounds dirty. I feel weird just typing it.

You're probably not old enough to have had a walkman?

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