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!

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.