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Wednesday, August 18, 2010

box of marbles redux

If you enjoy the box of marbles demo, now we extend it to include some basic network support. The premise is simple, look at this short video first (or watch on YouTube):

The code to handle the physics of the marbles remains the same, i.e. we just use Chipmunk physics engine. However, I added a simple feature to transfer marbles from one place to another. To keep it simple, it is done using UDP. The Qt network module supports UDP quite well, making the datagram code short and readable.

The intended use of this example is easy: run the desktop version and then run the mobile version (tested with Nokia N900). Each instance should find each other and start communicating. Again, we simplify the situation here and handle only 2 (two) peers. To facilitate troubleshooting, the application window title will contain the network address information, if the two peers are fully connected. To avoid complicated setup, discovery is carried out automagically through broadcast. This makes such a demo runs only under the same subnet, which is not a big deal.

It would have been much more fun doing the transfer between two smartphones (instead of a phone and my laptop). However, I own only one Nokia N900. Hint: I will not refuse your donation of Nokia N8 or (preferably) MeeGo-powered Nokia N9 (i.e. the N900's successor, whatever the real name is).

If you want to give it a try, head to the usual X2 repository and look at demo/marblenet subdirectory. Again, have the patient to follow the README file before you start compiling it.

Of course, feel free to extend this example to suit your (more wild) fantasy!

Wednesday, August 11, 2010

adventure to the land of green tea

Now I work for Sencha, the company behind the leading JavaScript frameworks such as Sencha Touch, Ext JS, Ext GWT, Ext Designer, jQTouch, Raphaël, Connect, which empower developers to create, deploy and optimize application using web-standard technologies (HTML5, CSS, JavaScript). Beside, it's a hot startup to work for.

quattro cinque

It's released!

Tuesday, August 10, 2010

box of marbles

The next logical step after simple bouncing ball example is something which uses a real, full-featured physics engine. Box2D is usually the popular choice. Combining Box2D with Qt has been done by many people, recently demonstrated before by Andreas and Thorbjørn. I decided to pick something else, i.e. Chipmunk physics engine.

Because this is supposed to an example, I tried to make it as simple as possible (you'd be able to extend it, once you grab the basics). Basically we have a box full of colorful marbles (yes, I loved to play marbles when I was a kid, there was not any PlayStation back then). A mouse click, or a screen tap, will generated a new marble with a random color. If you run the example on Nokia N900, you can control how the marbles move and hit each other by tilting and shaking the phone.

Check the code yourself at the usual X2 repository under the demo/marblebox subdirectory. Make sure you open and follow the instructions in the included README file.

For a sneak peek, just watch this video (or enjoy on YouTube).

There is still a sequel to this marble box. And still with Chipmunk.

what is it with this froyo obsession

Eclair still rocks :)


Monday, August 09, 2010

bouncing ball with accelerometer on N900

First of all, I apologize for my laziness in updating X2 with new code example. I have actually written quite a number of interesting examples, some of which have even been shown back in March, during my talk at Bossa Conference 10, though I did not find the time to clean up and polish them. Although I'd face new challenges in my upcoming adventure, I am quite confident I will reach the designated rate of new X2 example fortnightly.

Now let's focus on the newest example: a minor modification to the previous accelerometer code on Nokia N900 [1]. There has been confusion with my statement there: put this function is a separate thread. This is the alternative to a non-blocking D-Bus code. The main goal of course is not to be able to get faster acceleration values per second, it is only to prevent your code from being blocked by the synchronous D-Bus call.

Rather than just updating the code with the threaded version, I also added some high-school Newtonian physics. Instead of boring sliders, you'll get a ball which moves based on the acceleration [2], i.e. it follows the gravity if you keep your N900 straight.

Here is the obligatory video. Or watch directly on YouTube.

The code can be found in the X2 repository under the sensor/bouncingball subdirectory.

In the next installment, we will integrate a third-party real physics engine and make the example more alive!

[1] Another approach is to use Qt Mobility. However, QTMOBILITY-381 (which was spawn from QTMOBILITY-326) has not been solved yet (as of today).
[2] The overall math is not too scientifically correct, but hey, I always need to leave out something, for your homework :P

Friday, August 06, 2010

even LOST has its season finale

the final countdown

Today is my last day at Qualcomm.

It still feels like yesterday when I set foot in this continent, started some fun with X2, enjoyed Brazil, had this meet-up in Cupertino, did little exploration around San Diego, and then got blessed with a cute boy. Time really flies. Now it's already time to move on, again (though this time without a geeky resignation).

I will miss Snapdragon (the pictured HTC EVO is powered by the said platform). Or any other dragons.

Those who are annoyed by a certain obsession of mine probably can guess where I'm heading to. In the grand mission of inspiring and pushing developers to write better and more exciting applications, a particular productivity barrier needs to be broken. And I dropped enough (subtle) hints in my previous blog entries already.

Stay tuned.

Monday, August 02, 2010

crowdsourcing for the win

In some news, MapQuest embraces OpenStreetMap, launches the maps site at using the data from OpenStreetMap, as well as sets aside $1 million funding to improve the maps situation in USA. Let's see if other maps services will follow.