Pinch to zoom in libgdx

So I was a bit confused how to reproduce the multitouch gesture you often see in mobile gallery apps using libgdx. The idea is to zoom and recenter the viewport such that the points where your fingers are anchored are always the same (in game coordinates). Assuming you don’t need to rotate, here is the code I came up with:

Of course, you shouldn’t put all this stuff into this method: each logical piece of code should be in its own method (and in minesweeper most of it is actually on another object, since I like to have only code relating to gesture handling on the gesture handler object)

A lovely new minesweeper on android I made

Today I am finally releasing my little minesweeper for android! I’ve been working on this as a hobby for the past few weekends, and now it is finally smooth enough to let other people see it! The problem with most minesweeper applications in the market is that they are either really ugly or haven’t really figured out how to adapt the original mouse controls to a touchscreen. I set out to solve these two problems so I can play some mines on my phone!

To solve the ugliness problem, I drew some tiles in photoshop in a very minimal style, to disturb the eyes as little as possible and let you focus on the game. Here is how it turned out.

mines on the nexus 7
mines on the nexus 7 (click to open full res; kind of depressing how a screenshot from a tiny tablet doesn’t fit my 15′ macbook pro’s screen at 100% resolution)

To navigate the board, you can use the normal multitouch gestures like pan and pinch to zoom. To place a flag, you can long press a tile or you can double tap an open tile and drag to a closed tile (these gestures won’t let you win speed competitions, but they’re pretty good if you’re lazily solving the board)

drag from an open tile...
drag from an open tile…
and put a flag
and put a flag

You also get some pretty sweet statistics when you win or lose!




Download it here!

Rays for android

Another platform I had a go at porting the rays app for was android. This was probably the least enjoyable port I’ve done, not because of the Java language but because there is essentially no decent library to do the kinds of 2D effects the app requires.

I researched a bit on the topic and there were three ways to go about doing this:

  • Use android’s own openGL implementation.
  • Use the NDK to write native code which draws directly to the framebuffer.
  • Use libGDX.

At the time (well over a year ago, before the fancy new android developers redesign) documentation for the first two options was absolutely incomprehensible. Even now I find using the openGL implementation in android quite confusing, although it might be my fault as I never really learned low level openGL. I now feel tempted to use the much improved NDK and do some low level pixel manipulation, but other projects take priority…

I ended up using libGDX. It was also poorly documented (some random wiki pages + code comments) but the API made a lot more sense to me. This is because it was in the vein of some 2D libraries for the NDS such as the venerable PAlib and uLibrary which I used extensively previously (in hindsight, it appears they were not the best libraries in terms of code quality and the simple libNDS would have been a much better choice). The fact that you could instantly play the game on your computer natively without needing an emulator also helped. Though I would recommend just plugging in your android device and debugging directly there, Android’s debugger is truly excellent.

The library was chosen, the code was banged out, et voila! It lives! No antialiasing, no funky glow effects but it lives!

Rays app running on Galaxy S2
Rays app running on Galaxy S2

One idea I had to make the app more interesting would be to synthesize some musical instrument, something like a violin, where each instrument would be represented by a ray, with the intensity of the sound proportional to its speed. I could not find any satisfactory samples though, since they all come as single notes and I’d rather have some continuous sound produced. It might be more interesting to use some sort of synthesis algorithm to produce an interesting sound and modulate its amplitude, frequency or harmonics with the rays. How to go about it remains a mystery  There aren’t too many synthesis libraries available for android that do what I want. Libpd seems to be a decent option, now I just need to find the time to finish this project.

Since the application has only been tested on a handful of phones, I never did toss it on the play store. Get it here if you want to play with it. You’ll have to allow installation of non market apps.