Impact JavaScript Game Engine for iOS

http://www.phoboslab.org/log/2010/10/impact-for-ios

by phoboslab • 16 years ago

133 22 16 years ago

wensing• 16 years ago

Can someone summarize the impact (no pun intended) of this?

maushu• 16 years ago

Make multimedia software, generally games, for iPhone/iPod Touch/iPad using javascript and html5 canvas and make it run almost as fast as a native version.

teamonkey• 16 years ago

It is a native app: it uses JavaScriptCore and all Canvas calls are rendered using OpenGL. The implications are that if you write a game for Impact engine you can generate an iOS native app.

jws• 16 years ago

Summary: Technology demo wherein the author takes a Javascript game, runs it as an App (no browser) using OpenGL instead of <canvas> and the Javascript interpreter already in the iPhone for the drawing and gets 60fps.

• The Javascript interpreter interface used is considered private and thus the app can not be distributed in the store.

• There is a history of private to public interface transitions, so perhaps…

• It suggests you could have all the game code be common between a web and a higher performance app version of a game.

• No word in the article about what percent speedup this represents.

phoboslab2• 16 years ago

The speedup is substantial, at least in this case. Biolab Disaster has to draw lots of small 8x8 pixel squares (about 500 for each frame) to produce the background map - which seems to be awfully slow in the iOS browser.

Running in the browser, I had about 10 frames per second as noted in my previous blog post: http://www.phoboslab.org/log/2010/09/biolab-disaster

dstein• 16 years ago

This sounds like some really, really great stuff. As it is, canvas in Safari/IOS is simply too slow to make any fast action game in JavaScript.

jawngee• 16 years ago

You can bundle the JavaScriptCore with your iOS and be legal for the app store, you just can't use the private API.

albertzeyer• 16 years ago

On the homepage of the game, he says that the web version runs with about 12FPS on the iPhone. So he got about 500% speedup by this.

apike2• 16 years ago

There's a lot of interest in the mobile and JavaScript communities for a JavaScript engine you can distribute on iOS. Games are one thing, but with this you could take cross-platform, natively packaged web apps to a whole new level.

jrnkntl• 16 years ago

Sort of like an even more native Titanium Appcelerator? < http://appcelerator.com >

apike2• 16 years ago

Exactly, or like PhoneGap. For example, you could write an Appcelerator or PhoneGap app and call into native code from a JavaScript bridge. Right now, each native API needs to be explicitly wrapped by Appcelerator or PhoneGap.

empire29• 16 years ago

So it sounds like the source code for game is written in pure javascript (utilizing any special APIs calls provided by Impact). This javascript src is packaged using the Impact Game Engine which creates a Obj-C wrapper around the javascript. When the Game is loaded on an iOS device and run, the Obj-C wrapper (implemented by Impact) executes the javascript src via JavascriptCore.

It sounds like this is basically a Canvas to OpenGL translation layer.

Can only the Canvas object be leveraged when creating games/apps with this? Or could a "account creation" screen be created leveraging HTML elements like forms (I would assume not since its sounds like its executed outside of Safari, and the translation provided is from Canvas > OpenGL)

icefox• 16 years ago

Yah, the original game is all in pure javascript written to the canvas. I have been poking around with making canvas apps and a few weeks ago I grabbed the source and spent a few hours reading through all of it. Good stuff. If the author wasn't in Poland (corporate doesn't have an office there) I would try to hire him.

st3fan2• 16 years ago

"The JavaScriptCore Framework is still private on iOS. So as it is now, I won't be allowed to distribute the game in the AppStore. But my understanding is, that if I bundle my own copy of the JavaScriptCore Framework (which is part of WebKit and thus freely available) with my game, I should be on the safe side."

This is true. You can compile Javascript Core and include it in your app. I have done this previously as an experiment.

However, there is one HUGE drawback in doing so: no compiled/jitted javascript code is possible.

This is because iOS applications are not allowed to create executable code in the heap or on the stack, so there is no way for JavaScriptCore to compile to native code when it is running as part of a third party application.

So unfortunately there is no good way to get this going at the same speed that you get when linking against the private framework.

Sad. This is also a major problem for other scripting languages. They all can only run in interpreted mode. Which might be good enough but is never the best you can get.

AntiRush2• 16 years ago

Yep, I hit this roadblock too. For my similar project I ended up using a non-jit version of Spidermonkey for embedded Javascript. Interpreted performance is pretty poor in comparison to jit though, and I ended up moving to a much higher level Javascript API to share between canvas and native implementations. It runs at 60 fps on 2nd gen hardware now with moderate (1 - 2 hundred sprites).

wtracy• 16 years ago

Just thinking out loud:

I wonder how feasible it would be to pre-compile the Javascript to machine code before distributing it? Maybe someone determined enough could probably hack one of the existing JIT engines to emit executable machine code to a file?

Impact JavaScript Game Engine for iOS

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