Nokia Qt-Developers Contest

On a boring Friday afternoon I was just boarding the bus, coming home from the university when a friend of mine called me and told me about the Nokia Qt-Developers Contest organized by Nokia Romania.

We immediately established a team and went to the most silent pub we could find in Cluj for brainstorming.

The idea we ended up deciding on was my idea, inspired by looking at the ncmpc source code which I studied for building the 2d spectrum analyzer.

Basically the idea is to write a mobile MPD (Music Player Daemon) client. This is not special, there are many MPD Clients (MPC for simplicity) for every platform known to man. But MPD has http streaming and can basically stream your music back at you like a Shoutcast/Icecast radio station.

So our idea is to write a music player which lets you remotely control playback on your server and connect to the radio-stream and play it back, thus eliminating the need to store your huge N GB collection on a small memory card and leaving space for other stuff.
There are many technical problems with this idea, one is the data traffic cost, so you have to be on unlimited 3G data-plan or on a wireless connection (but these things are not as rare nowadays). The other is network latency (we need to carefully plan buffering) and also the effect on battery life.

So yeah, there are many challenges but if other projects could do similar things, it probably means it's possible and I have seen many great things happen under Qt.

I have already coded a working prototype , I am still battling Phonon because it doesn't really want to do what I tell it to, maybe I will rewrite the player part in QtMultimedia, we shall see.

I like this idea and I find it fun to code, mainly because I think it's relatively original (point me to a working implementation on a mobile platform if you think otherwise).

The other reason why I chose this idea is that it fits the spirit of Symbian and Nokia phones in general, since it targets as it's main audience the geeks, the power users, people who buy Symbian phones to connect through ssh to their server.
This is even more so in our days when Symbian is basically dead, Nokia abandoned it for Windows Mobile, so mainly the people who buy/have Symbian ^3 phones are developers/power users/geeks/business guys.

Even though this app doesn't seem very marketable for average users I believe there is a need for such a thing in the Symbian/Maemo/Meego/Android/Qt crowd.

Oh yeah, and now if we write it in Qt, the Android guys can use it too, thanks to a Romanian hacker named Bogdan Vatra.

I'm not sure that this is the most competitive idea on the list but feel free to vote for anything you like on this link.


Also this app would enable friends to connect to the same server and listen to the same song at the same time and also control playback.


So yeah, wish us luck! :)

Visualizing Music - Part 2

I've finally managed to fix the crash.It was quite an ugly race condition, the rendering thread wanted access to the same scene node as the music playback thread, it's not exactly clear where and why, it's hidden in the internals of Ogre, I guess.
Anyway, I've managed to fix it by locking on the same semaphore as used in the callback function in frameStarted() and unlocking it in frameEnded(). So it's finally working, thanks to my friend for pointing it out. Release comming soon.

Meanwhile, I've been experimenting a bit with perl, I rewrote the SDL Music Visualizer example to render a frequency spectrum (aka bars).
I found a nice module for doing the Fourier Transform, Math::FFT.

You can find the code here: https://github.com/balazsbela/Visualizer/blob/master/frequency.pl

And here's a screenshot:




All this in 210 lines of Perl. Perl is indeed awesome.

Visualizing music

Not long ago I came across this article: http://www.perl.com/pub/2011/01/visualizing-music-with-sdl-and-perl.html

Now, I'm no stranger to perl, I have used it before, mainly for socket programming and http requests, I knew it had various bindings for various libraries, but still this solution seemed elegant.

This gave me the idea to recreate this old xmms spectrum analyzer OpenGL plugin with Ogre3d.

I had two weeks vacation between semester 2 and 3 so I had time to study a bit of OpenGL to help me draw things in my (optional) Computational Geometry class.

So I read about the fast fourier transform and how to extract the frequencies out of the stream. I decided to use FFTW because it's fast and I came up with a solution to normalize the values (not sure if it's the best, but it works, if you have tips on how to do this more correctly I'm very eager to hear them).

I came up with this code:

https://github.com/balazsbela/OgreVisualizer



It works, it plays ogg files and visualizes them in 3d pretty well. The framerate is pretty good too.

There is one problem though, it crashes after a while,seemingly randomly, sometimes it
plays through the whole song without problems, sometimes it crashes at the half of the song.

I posted questions on Ogre3d forum, StackExchange GameDev section, Stackoverflow, but I have yet to read a good response.

Here's the main class: https://github.com/balazsbela/OgreVisualizer/blob/master/src/VisualizerApplication.cpp

Here's the backtrace:

balazsbela@darknet:~/workspace/OgreVisualizer/Release$ gdb OgreVisualizer core
GNU gdb (GDB) 7.2-debian
Copyright (C) 2010 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law. Type "show copying"
and "show warranty" for details.
This GDB was configured as "i486-linux-gnu".
For bug reporting instructions, please see:
...
Reading symbols from /home/balazsbela/workspace/OgreVisualizer/Release/OgreVisualizer...done.
[New Thread 17705]
[New Thread 17702]
[New Thread 17703]
[New Thread 17700]
Reading symbols from /usr/lib/libv4l/v4l1compat.so...(no debugging symbols found)...done.
Loaded symbols for /usr/lib/libv4l/v4l1compat.so
Reading symbols from /usr/local/lib/libOgreMain.so.1.7.1...done.
Loaded symbols for /usr/local/lib/libOgreMain.so.1.7.1
Reading symbols from /usr/lib/libfftw3.so.3...(no debugging symbols found)...done.
Loaded symbols for /usr/lib/libfftw3.so.3
Reading symbols from /usr/lib/libSDL_sound-1.0.so.1...(no debugging symbols found)...done.
Loaded symbols for /usr/lib/libSDL_sound-1.0.so.1
Reading symbols from /usr/lib/libSDL-1.2.so.0...(no debugging symbols found)...done.
Loaded symbols for /usr/lib/libSDL-1.2.so.0
Reading symbols from /usr/lib/libSDL_mixer-1.2.so.0...(no debugging symbols found)...done.
Loaded symbols for /usr/lib/libSDL_mixer-1.2.so.0
Reading symbols from /usr/lib/libOIS-1.2.0.so...(no debugging symbols found)...done.
Loaded symbols for /usr/lib/libOIS-1.2.0.so
Reading symbols from /usr/lib/libstdc++.so.6...(no debugging symbols found)...done.
Loaded symbols for /usr/lib/libstdc++.so.6
Reading symbols from /lib/i686/cmov/libm.so.6...Reading symbols from /usr/lib/debug/lib/i686/cmov/libm-2.11.2.so...done.
done.
Loaded symbols for /lib/i686/cmov/libm.so.6
Reading symbols from /lib/libgcc_s.so.1...(no debugging symbols found)...done.
Loaded symbols for /lib/libgcc_s.so.1
Reading symbols from /lib/i686/cmov/libc.so.6...Reading symbols from /usr/lib/debug/lib/i686/cmov/libc-2.11.2.so...done.
done.
Loaded symbols for /lib/i686/cmov/libc.so.6
Reading symbols from /lib/i686/cmov/libpthread.so.0...Reading symbols from /usr/lib/debug/lib/i686/cmov/libpthread-2.11.2.so...done.
done.
Loaded symbols for /lib/i686/cmov/libpthread.so.0
Reading symbols from /usr/local/lib/libv4l1.so.0...done.
Loaded symbols for /usr/local/lib/libv4l1.so.0
Reading symbols from /usr/lib/libfreetype.so.6...(no debugging symbols found)...done.
Loaded symbols for /usr/lib/libfreetype.so.6
Reading symbols from /usr/lib/libSM.so.6...(no debugging symbols found)...done.
Loaded symbols for /usr/lib/libSM.so.6
Reading symbols from /usr/lib/libICE.so.6...(no debugging symbols found)...done.
Loaded symbols for /usr/lib/libICE.so.6
Reading symbols from /usr/lib/libX11.so.6...(no debugging symbols found)...done.
Loaded symbols for /usr/lib/libX11.so.6
Reading symbols from /usr/lib/libXext.so.6...(no debugging symbols found)...done.
Loaded symbols for /usr/lib/libXext.so.6
Reading symbols from /usr/lib/libXt.so.6...(no debugging symbols found)...done.
Loaded symbols for /usr/lib/libXt.so.6
Reading symbols from /usr/lib/libXaw.so.7...(no debugging symbols found)...done.
Loaded symbols for /usr/lib/libXaw.so.7
Reading symbols from /lib/i686/cmov/libdl.so.2...Reading symbols from /usr/lib/debug/lib/i686/cmov/libdl-2.11.2.so...done.
done.
Loaded symbols for /lib/i686/cmov/libdl.so.2
Reading symbols from /usr/lib/libboost_thread.so.1.42.0...(no debugging symbols found)...done.
Loaded symbols for /usr/lib/libboost_thread.so.1.42.0
Reading symbols from /usr/lib/libboost_date_time.so.1.42.0...(no debugging symbols found)...done.
Loaded symbols for /usr/lib/libboost_date_time.so.1.42.0
Reading symbols from /usr/lib/libfreeimage.so.3...(no debugging symbols found)...done.
Loaded symbols for /usr/lib/libfreeimage.so.3
Reading symbols from /usr/lib/libzzip-0.so.13...(no debugging symbols found)...done.
Loaded symbols for /usr/lib/libzzip-0.so.13
Reading symbols from /usr/lib/libz.so.1...(no debugging symbols found)...done.
Loaded symbols for /usr/lib/libz.so.1
Reading symbols from /usr/lib/libsmpeg-0.4.so.0...(no debugging symbols found)...done.
Loaded symbols for /usr/lib/libsmpeg-0.4.so.0
Reading symbols from /usr/lib/libmikmod.so.2...(no debugging symbols found)...done.
Loaded symbols for /usr/lib/libmikmod.so.2
Reading symbols from /usr/lib/libvorbis.so.0...(no debugging symbols found)...done.
Loaded symbols for /usr/lib/libvorbis.so.0
Reading symbols from /usr/lib/libvorbisfile.so.3...(no debugging symbols found)...done.
Loaded symbols for /usr/lib/libvorbisfile.so.3
Reading symbols from /usr/lib/libFLAC.so.8...(no debugging symbols found)...done.
Loaded symbols for /usr/lib/libFLAC.so.8
Reading symbols from /usr/lib/libogg.so.0...(no debugging symbols found)...done.
Loaded symbols for /usr/lib/libogg.so.0
Reading symbols from /usr/lib/sse2/libspeex.so.1...(no debugging symbols found)...done.
Loaded symbols for /usr/lib/sse2/libspeex.so.1
Reading symbols from /usr/lib/libasound.so.2...(no debugging symbols found)...done.
Loaded symbols for /usr/lib/libasound.so.2
Reading symbols from /lib/i686/cmov/librt.so.1...Reading symbols from /usr/lib/debug/lib/i686/cmov/librt-2.11.2.so...done.
done.
Loaded symbols for /lib/i686/cmov/librt.so.1
Reading symbols from /usr/lib/libdirectfb-1.2.so.9...(no debugging symbols found)...done.
Loaded symbols for /usr/lib/libdirectfb-1.2.so.9
Reading symbols from /usr/lib/libfusion-1.2.so.9...(no debugging symbols found)...done.
Loaded symbols for /usr/lib/libfusion-1.2.so.9
Reading symbols from /usr/lib/libdirect-1.2.so.9...(no debugging symbols found)...done.
Loaded symbols for /usr/lib/libdirect-1.2.so.9
Reading symbols from /usr/lib/libvga.so.1...(no debugging symbols found)...done.
Loaded symbols for /usr/lib/libvga.so.1
Reading symbols from /lib/ld-linux.so.2...Reading symbols from /usr/lib/debug/lib/ld-2.11.2.so...done.
done.
Loaded symbols for /lib/ld-linux.so.2
Reading symbols from /usr/local/lib/libv4l2.so.0...done.
Loaded symbols for /usr/local/lib/libv4l2.so.0
Reading symbols from /lib/libuuid.so.1...(no debugging symbols found)...done.
Loaded symbols for /lib/libuuid.so.1
Reading symbols from /usr/lib/libxcb.so.1...(no debugging symbols found)...done.
Loaded symbols for /usr/lib/libxcb.so.1
Reading symbols from /usr/lib/libXmu.so.6...(no debugging symbols found)...done.
Loaded symbols for /usr/lib/libXmu.so.6
Reading symbols from /usr/lib/libXpm.so.4...(no debugging symbols found)...done.
Loaded symbols for /usr/lib/libXpm.so.4
Reading symbols from /usr/lib/libjpeg.so.62...(no debugging symbols found)...done.
Loaded symbols for /usr/lib/libjpeg.so.62
Reading symbols from /usr/lib/libmng.so.1...(no debugging symbols found)...done.
Loaded symbols for /usr/lib/libmng.so.1
Reading symbols from /usr/lib/libopenjpeg.so.2...(no debugging symbols found)...done.
Loaded symbols for /usr/lib/libopenjpeg.so.2
Reading symbols from /lib/libpng12.so.0...(no debugging symbols found)...done.
Loaded symbols for /lib/libpng12.so.0
Reading symbols from /usr/lib/libIlmImf.so.6...(no debugging symbols found)...done.
Loaded symbols for /usr/lib/libIlmImf.so.6
Reading symbols from /usr/lib/libImath.so.6...(no debugging symbols found)...done.
Loaded symbols for /usr/lib/libImath.so.6
Reading symbols from /usr/lib/libHalf.so.6...(no debugging symbols found)...done.
Loaded symbols for /usr/lib/libHalf.so.6
Reading symbols from /usr/lib/libIex.so.6...(no debugging symbols found)...done.
Loaded symbols for /usr/lib/libIex.so.6
Reading symbols from /usr/lib/libIlmThread.so.6...(no debugging symbols found)...done.
Loaded symbols for /usr/lib/libIlmThread.so.6
Reading symbols from /lib/libx86.so.1...(no debugging symbols found)...done.
Loaded symbols for /lib/libx86.so.1
Reading symbols from /usr/local/lib/libv4lconvert.so.0...done.
Loaded symbols for /usr/local/lib/libv4lconvert.so.0
Reading symbols from /usr/lib/libXau.so.6...(no debugging symbols found)...done.
Loaded symbols for /usr/lib/libXau.so.6
Reading symbols from /usr/lib/libXdmcp.so.6...(no debugging symbols found)...done.
Loaded symbols for /usr/lib/libXdmcp.so.6
Reading symbols from /usr/lib/liblcms.so.1...(no debugging symbols found)...done.
Loaded symbols for /usr/lib/liblcms.so.1
Reading symbols from /usr/local/lib/OGRE/RenderSystem_GL.so...done.
Loaded symbols for /usr/local/lib/OGRE/RenderSystem_GL.so
Reading symbols from /usr/lib/libGLU.so.1...(no debugging symbols found)...done.
Loaded symbols for /usr/lib/libGLU.so.1
Reading symbols from /usr/lib/libGL.so.1...(no debugging symbols found)...done.
Loaded symbols for /usr/lib/libGL.so.1
Reading symbols from /usr/lib/libXrandr.so.2...(no debugging symbols found)...done.
Loaded symbols for /usr/lib/libXrandr.so.2
Reading symbols from /usr/lib/libGLcore.so.1...(no debugging symbols found)...done.
Loaded symbols for /usr/lib/libGLcore.so.1
Reading symbols from /usr/lib/tls/libnvidia-tls.so.1...(no debugging symbols found)...done.
Loaded symbols for /usr/lib/tls/libnvidia-tls.so.1
Reading symbols from /usr/lib/libXrender.so.1...(no debugging symbols found)...done.
Loaded symbols for /usr/lib/libXrender.so.1
Reading symbols from /usr/lib/libXcursor.so.1...(no debugging symbols found)...done.
Loaded symbols for /usr/lib/libXcursor.so.1
Reading symbols from /usr/lib/libXfixes.so.3...(no debugging symbols found)...done.
Loaded symbols for /usr/lib/libXfixes.so.3
Reading symbols from /lib/i686/cmov/libnss_compat.so.2...Reading symbols from /usr/lib/debug/lib/i686/cmov/libnss_compat-2.11.2.so...done.
done.
Loaded symbols for /lib/i686/cmov/libnss_compat.so.2
Reading symbols from /lib/i686/cmov/libnsl.so.1...Reading symbols from /usr/lib/debug/lib/i686/cmov/libnsl-2.11.2.so...done.
done.
Loaded symbols for /lib/i686/cmov/libnsl.so.1
Reading symbols from /lib/i686/cmov/libnss_nis.so.2...Reading symbols from /usr/lib/debug/lib/i686/cmov/libnss_nis-2.11.2.so...done.
done.
Loaded symbols for /lib/i686/cmov/libnss_nis.so.2
Reading symbols from /lib/i686/cmov/libnss_files.so.2...Reading symbols from /usr/lib/debug/lib/i686/cmov/libnss_files-2.11.2.so...done.
done.
Loaded symbols for /lib/i686/cmov/libnss_files.so.2
Reading symbols from /usr/lib/alsa-lib/libasound_module_rate_speexrate.so...(no debugging symbols found)...done.
Loaded symbols for /usr/lib/alsa-lib/libasound_module_rate_speexrate.so
Reading symbols from /usr/lib/sse2/libspeexdsp.so.1...(no debugging symbols found)...done.
Loaded symbols for /usr/lib/sse2/libspeexdsp.so.1
Core was generated by `./OgreVisualizer'.
Program terminated with signal 11, Segmentation fault.
#0 0xb6dc563d in std::_Rb_tree_insert_and_rebalance(bool, std::_Rb_tree_node_base*, std::_Rb_tree_node_base*, std::_Rb_tree_node_base&) ()
from /usr/lib/libstdc++.so.6
(gdb) bt
#0 0xb6dc563d in std::_Rb_tree_insert_and_rebalance(bool, std::_Rb_tree_node_base*, std::_Rb_tree_node_base*, std::_Rb_tree_node_base&) ()
from /usr/lib/libstdc++.so.6
#1 0xb73bb3c2 in std::_Rb_tree, std::less, Ogre::STLAllocator > >::_M_insert_(std::_Rb_tree_node_base const*, std::_Rb_tree_node_base const*, Ogre::Node* const&) ()
from /usr/local/lib/libOgreMain.so.1.7.1
#2 0xb73b5a52 in _M_insert_unique (this=0xb6157ea0, child=0xb616aff8, forceParentUpdate=false) at /usr/include/c++/4.4/bits/stl_tree.h:1182
#3 insert (this=0xb6157ea0, child=0xb616aff8, forceParentUpdate=false) at /usr/include/c++/4.4/bits/stl_set.h:411
#4 Ogre::Node::requestUpdate (this=0xb6157ea0, child=0xb616aff8, forceParentUpdate=false)
at /home/balazsbela/Downloads/ogre_src_v1-7-1/OgreMain/src/OgreNode.cpp:805
#5 0xb73b6a40 in Ogre::Node::needUpdate (this=0xb616aff8, forceParentUpdate=92)
at /home/balazsbela/Downloads/ogre_src_v1-7-1/OgreMain/src/OgreNode.cpp:789
#6 0xb73b5038 in Ogre::Node::setScale (this=0x1825c, scale=...) at /home/balazsbela/Downloads/ogre_src_v1-7-1/OgreMain/src/OgreNode.cpp:638
#7 0x0805d306 in VisualizerApplication::adjustNodes (this=0x9cd4808) at ../src/VisualizerApplication.cpp:236
#8 0xb6e867f0 in ?? () from /usr/lib/libSDL_mixer-1.2.so.0
#9 0xb6e8719a in ?? () from /usr/lib/libSDL_mixer-1.2.so.0
#10 0xb6ed9b0d in ?? () from /usr/lib/libSDL-1.2.so.0
#11 0xb6ee185e in ?? () from /usr/lib/libSDL-1.2.so.0
#12 0xb6f2e0bd in ?? () from /usr/lib/libSDL-1.2.so.0
#13 0xb6bc7955 in start_thread (arg=0xb198ab70) at pthread_create.c:300
#14 0xb6ca6e7e in clone () at ../sysdeps/unix/sysv/linux/i386/clone.S:130
(gdb)

I've had this bug for weeks, it's very frustrating.
It seems like Ogre keeps an std::set with the Nodes which need updating, this std::set is a Red Black Tree.

It instantly crashes once the node gets into the set at one point.
I used the sdl semaphores to make sure that the callback function does not call visualize multiple times, before the previous call finished.

I don't know what causes this crash. Maybe the std::set fills up from the frequent updating ? Maybe I should limit the framerate ?

I tried using a NodeListener to only update a node if the previously queued update operation finished, but since it crashes when it's placed in the update queue, not when it gets updated, it didn't help.


Relevant methods for the crash, snippets from Ogre3d 1.7.1 source code:

void Node::setScale(const Vector3& scale)
{
assert(!scale.isNaN() && "Invalid vector supplied as parameter");
mScale = scale;
needUpdate();
}

void Node::requestUpdate(Node* child, bool forceParentUpdate)
{
// If we're already going to update everything this doesn't matter
if (mNeedChildUpdate)
{
return;
}

mChildrenToUpdate.insert(child);
// Request selective update of me, if we didn't do it before
if (mParent && (!mParentNotified || forceParentUpdate))
{
mParent->requestUpdate(this, forceParentUpdate);
mParentNotified = true ;
}

}

typedef set::type ChildUpdateSet;

/// List of children which need updating, used if self is not out of date but children are
mutable ChildUpdateSet mChildrenToUpdate;

STL Set:

// insert/erase
/**
* @brief Attempts to insert an element into the %set.
* @param x Element to be inserted.
* @return A pair, of which the first element is an iterator that points
* to the possibly inserted element, and the second is a bool
* that is true if the element was actually inserted.
*
* This function attempts to insert an element into the %set. A %set
* relies on unique keys and thus an element is only inserted if it is
* not already present in the %set.
*
* Insertion requires logarithmic time.
*/
std::pair
insert(const value_type& __x)
{
std::pair __p =
_M_t._M_insert_unique(__x);
return std::pair(__p.first, __p.second);
}

STL Tree:

template
pair::iterator, bool>
_Rb_tree<_key,>::
_M_insert_unique(const _Val& __v)
{
_Link_type __x = _M_begin();
_Link_type __y = _M_end();
bool __comp = true;
while (__x != 0)
{
__y = __x;
__comp = _M_impl._M_key_compare(_KeyOfValue()(__v), _S_key(__x));
__x = __comp ? _S_left(__x) : _S_right(__x);
}
iterator __j = iterator(__y);
if (__comp)
{
if (__j == begin())
return pair(_M_insert_(__x, __y, __v), true);
else
--__j;
}
if (_M_impl._M_key_compare(_S_key(__j._M_node), _KeyOfValue()(__v)))
return pair(_M_insert_(__x, __y, __v), true);
return pair(__j, false);
}

template
typename _Rb_tree<_key,>::iterator
_Rb_tree<_key,>::
_M_insert_equal(const _Val& __v)
{
_Link_type __x = _M_begin();
_Link_type __y = _M_end();
while (__x != 0)
{
__y = __x;
__x = _M_impl._M_key_compare(_KeyOfValue()(__v), _S_key(__x)) ?
_S_left(__x) : _S_right(__x);
}
return _M_insert_(__x, __y, __v);
}

So yeah, this bug is a stubborn one.
If you would like to build the source code I will provide the instructions to do so, I also compiled it under windows, I have a build if you need it. If anyone has any idea how to fix the crash, I would be willing to donate beer :)).

For now, here's a screenshot:



Oh yeah, and you have full control of the camera, like in OgrePathfinder.

OgrePathFinder

I was always interested in graphics/game programming, so after an XNA/Blender workshop held at the faculty I've started to look into OpenGL programming.
I had a few adventures with OpenGL and SDL, GLUT and other tools meant to make life with OpenGL easier. I have studied a few mesh loaders (obj and md2), but I soon realized the limitations of this form of development.
Then I heard about Ogre3d, the Object-Oriented Graphics Rendering Engine.
So I've looked into their tutorials and started studying it. After a few Hello World- like applications I have decided to go more in-depth. I studied the topics of Scene Managers, Scene Graphs, Lights, Cameras, Animations and whatnot.

To put things in practice I've decided to write a simulation for my own implementation of the A* algorithm, written as an assignment at the university (from a list of problems, and we could choose the complexity of our solution).

Therefore, OgrePathFinder was born.
You can find the sourcecode and binaries (for Windows and Linux, since Ogre3d is cross-platform) at the Google code page:

http://code.google.com/p/ogrepathfinder/


Here is a youtube video demonstrating the application, complete with victory dance :




I have ported the Ogre Character sample from the Samples SDK to the Ogre3D wiki tutorial framework. Most of the resources (meshes, textures whatnot) are part of the Character sample. The only thing that I modeled in blender was the obstacle cube.


The movements are based on calculating the traveled distance with vectors and with checking their bounds at every frame, so the movement is framerate dependent. I also wanted to learn collision detection so I've added raycasting too.
You can see that the bounding boxes of obstacles in front of the character appear when touched by the ray. Raycasting is used to avoid walking in the front of an obstacle.
I've also included a smaller labyrinth. Just copy labyrinth.in.2 into labyrinth.in.


The motion is framerate dependent, all bound checks take place in the main render loop, so the character could take a wrong turn at some point, and think it arrived to the goal, but Ogre is only a graphics engine and I didn't use a physics engine like PhysX or Bullet.
The application seems to work well, but this is my first Ogre project, bugs may happen.

It could help beginners in learning Ogre.

Enjoy!

Introduction to Android

Now that the accepted GSoC projects were announced, I was informed that my proposal was not accepted.

The Maemo project got 87 proposals this year. Here you can find the list of accepted projects:

http://socghop.appspot.com/gsoc/org/home/google/gsoc2010/maemo

I asked my potential mentor (he commented on my proposal) about the reason my proposal was refused.

Valério Valério to me

show details Apr 26 (8 days ago)

Hello,

- Hide quoted text -

Bela Balazs wrote:

Hello.

I am sorry to waste your time. But I would like to ask why my GSoC proposal (http://socghop.appspot.com/document/show/user/balazsbela/maemotodo) was rejected.

I just want to know so that I can improve in the future. Please be very honest with me, I won't take it personally. I just want to know the reasons.

I understand that you got a lot a proposals and the places are very limited.

Just a few comments would satisfy my curiosity. What do you recommend for my next gsoc proposal.

Your proposal ranked 1/8 among the to-do application proposals, the simple reason was that we did not picked that project, otherwise your application would be chosen. I can't tell you what is in the private reviews, but is very positive.

From my side I can't point anything and would like to have you as student, due to your OSS background, but we can't pick all the projects :(.

Best regards,

Valério

Thank you very much.

So yeah, that's that. So many ideas in the idea list and only 10 projects get accepted.

I wish them good luck and may Maemo become competitive as soon as possible.

In the mean time I will spend my summer with learning new technologies.

One of these new technologies is Google's shiny new operating system: Android.

So I went ahead, installed the sdk, set up Eclipse and I've dived into Android development.

I wrote my own traditional Hello world type applications, the BMI Calculator.

Here are the images:

The message and the android image is changed according to the result, when Calculate is pressed.

I really like the development environment and the APIs seem cool. The designer is very limited though and I spent too much time searching trough the properties to get a design I'm satisfied with.

I hope they start supporting Qt soon, that would be awesome (since it would work on Maemo and other Qt supported platforms too). Still I don't know if this will be happening any time soon.

I miss signals and slots.

I'll continue to study Android development and if I get the hang of it, maybe I'll implement my GSoC proposal for the Android platform and publish it in the market.

Playing around with Maemo

Since Nokia acquired Trolltech we all knew that something awesome would come out of it. The days of Symbian and other slow and unstable mobile operating systems are coming to an end.

The best showcase of the Maemo operating system is the Nokia N900. Shiiiiiiny.

Now every time a good phone comes out people can't help compare it to the so called iPhone.

I deeply despise that device, and don't get me started on it because you'll get a post which you won't have the time to read.

I really think that we shouldn't trade our freedoms for sparkling, dumbed down interfaces under the banner of usability.

I have often been praised for the Keep Things Simple and Clean approach I took when designing the interface of qOrganizer, now I don't believe it's the best I could come up with, but even my 55 year old father can use it and that must mean something.

So back to Maemo, as you can see , despite having a touch screen, the N900 has a real keyboard which is something I can respect after being frustrated by writing sms-es on a touch screen (even with vibration and noise as feedback, it's just not the same).

I don't know enough about Android to compare Maemo to it, but my friend has an Android phone and it's pretty cool.

I went ahead and installed the Maemo SDK. This is fairly easy on Debian, you can find some instructions here. The Maemo SDK was brought to my attention in an e-mail by a user who suggested that I should port qOrganizer to it, so I went ahead and installed Qt in Scratchbox and tried to compile qOrganizer but some classes are missing(like QSystray and Printing related classes).

The Maemo operating system is simply a debian based linux, installed from scratch.

The package manager is fully integrated in the phone and it handles debian packages, which you can install from the shiny App manager interface of the phone or from the Scratchbox command line using apt-get, like on any Debian based system.

It can run any Qt application, and it has a great interface for them called Hildon.
Here you can see my classic BMI calculator (it's like a hello world for me) running in the SDK (with no modification to the code at all).

So Maemo has the full awesomeness of Debian package management combined with the best tools used to write Desktop Linux applications on the embedded mobile platform. It already has many free applications and it's basically community maintained and open source (take that Apple!). Freedom and ease of use. Now we only have to wait for the price to drop.

On a related note I have been thinking about participating in Google Summer of Code and I checked the idea list of the Maemo project and I've found this:

Advanced To-do list

Creating an advanced To-do list, with the ability to attach files, including audio recording, messages, emails, etc., linking multiple tasks and updating the priority of a task based on the time left

maemo SDK, Qt

The current To-do lists in most Nokia mobiles are disappointing. These added functionalities could make one's phone their own 24 hr assistant

It's listed under easy, but hey I'm in my first year, and that doesn't mean that I can't expand on the idea and make it powerful and easy to use. I think this would suit me well and I'll be working on my idea description this week. We'll see how it goes.

Wish me luck!

PS: Happy Easter y'all!

University Experiences

For those of you who have just tuned in: I am currently a student in the second semester of the first year at the English section of Computer Science at Babeş-Bolyai University in Cluj Napoca.

I have found the second semester a lot more interesting than the first, we currently learn Object Oriented Programming (in C++) and programming under Unix (fork(),exec() that stuff), pretty basic stuff, but essential.

I had the illusion that I would have time for development in my free time this semester. Boy was I wrong. Although we learn basic stuff, there is always a lot of work to do. I have laboratory projects that have to be properly documented (some documentations reach 20 pages) every week. That basically keeps me pretty busy, but as an extra feature my timetable is pretty intense and keeps sleep deprivation at a constant level. But other than that, I like it and it keeps me interested, I only wish I had more time for my own ideas. I have detailed in my last post some ideas I would like to implement in qOrganizer, but it needs serious work. I recently turned 20 and I'm not the 10th grader who wrote that application in 2006 without having any real ideas about good coding practices and software design decisions anymore, so I guess waiting for some technologies to mature and make it into Qt doesn't hurt (I'm looking at you MySQL embedded).

Anyway, qOrganizer is usable in it's current form and I can always work on smaller projects just for the fun of it.

Qt is great, and it's not a secret that I'm a great fan of it, but sometimes it makes the most basic things like capturing right clicks in a QCalendarWidget unnecessarily difficult.

Read this to get and idea what I'm talking about.