An EGLWindow class

I've just written a simple wrapper for the Raspberry Pi EGL Window / Config and the video core functions, it is a simple set of C++ classes which allows the creation of windows and setting of size etc. I will write a fuller post soon, but I thought I would upload the code and a simple video now.

The design is based in part on how the Qt QGLWidget works.

You can grab the code from here

Building a Raspberry PI Image Mac osx

I did some kernel tinkering earlier today and broke my main config so I decided to build two images on SD cards so I could have a stable vs un-stable boot image. The following discusses how to build an image using a mac book pro and the usual tools.

Initial SD image

I'm going to use the debian "squeeze" image from here and the terminal on the mac.

First it is easier if we do these operations as root so in the shell type sudo su and enter your password. Next we need to identify the disk in the card reader. In my case I did this using the following commands

mount

/dev/disk0s2 on / (hfs, local, journaled, noatime)
devfs on /dev (devfs, local, nobrowse)
/dev/disk1s2 on /Volumes/home (hfs, local, journaled)
/dev/disk1s3 on /Volumes/spare (hfs, local, journaled)
map -hosts on /net (autofs, nosuid, automounted, nobrowse)
map auto_home on /home (autofs, automounted, nobrowse)
localhost:/udRZrWiR2BXDgRrkJFCx2X on /Volumes/MobileBackups (mtmfs, nosuid, read-only, nobrowse)
/dev/disk3s1 on /Volumes/UNTITLED (msdos, local, nodev, nosuid, noowners)

In my case the disk in /Volumes/UNTITLED which is the device /dev/disk3s1, this is a mounted device so the first thing we need to do is unmount the partition so we can write to it. To do this we use the following

diskutil unmount /dev/disk3s1

Now we can proceed to write the disk image. This is a long process and it doesn't give any feedback whilst it is operating, however at the end it will report how many block written

dd bs=1m if=debian6-19-04-2012.img of=/dev/disk3
1859+1 records in
1859+1 records out
1950000000 bytes transferred in 1349.801573 secs (1444657 bytes/sec)

Now this is done we should be able to put it into the pi and boot  (username pi password raspberry)

Disk size

If we look at the partition on the disk we have just made you will see the following 

As you can see there is quite a bit of space not allocated and this is a bit of a problem if you want to install lots of software to the pi. There are a number of options we can take such as creating a new partition on the spare space and use this for home, or resize the DISK3S2 partition to a larger size.

I want to re-size the partition for ease of having a large home / root partition. The simplest method I've found for doing this is by using the linux gui but as I'm trying to keep this to mac / pi only I will use the method outlined here basically if you follow these instructions it works fine.

Getting updated

One of the first things you should do is update the packages installed. To do this we need to run the apt package manager. In the shell execute the following command

sudo apt-get update

I also decided to update my kernel to the latest version. The good news is that there is a really simple tool to do this, here I had to do the following to get it working

sudo apt-get install ca-certificates
sudo apt-get install git

Once this is done follow the instructions on the link

Adding a user

To add a user we use the unix adduser command. In my case I wanted to use jmacey as my username to sync with all of my other machines at home and work

adduser jmacey

By default this user doesn't have access to the administrator (root) account, so we need to add it to the sudoers file. This is done by using the visudo tool. This will open up an editor and we can add our new user as shown

pi      ALL=(ALL) ALL
jmacey  ALL=(ALL) ALL

In my case I've placed my username below the pi username, whilst I've left the pi user in, for security you may wish to remove this as it is a well known and documented username / password. To exit the editor use ctrl+k x to save and exit.

You should now be able to login as the new user and become root.

GPM

If you are used to other linux distros, you may be used to using the mouse in the terminal,  this is done using the gpm package. You can install it using

sudo apt-get install gpm

We now need to edit the config file to get the correct mouse device.

sudo vi /etc/gpm.conf
# now change the device line to
device=/dev/input/mouse0
# save then
sudo  /etc/init.d/gpm restart 

This should now give you a mouse in the terminal

Enable SSH on Boot for Raspberry PI

My usual development cycle using the raspberry pi is to use the mac and BBEdit via SSH to edit files and iTerm to ssh to get a shell. Whilst by default you can ssh from the pi, you need to enable ssh properly to work both ways.

The following will install and enable ssh on the debian "squeeze" build.

sudo apt-get install ssh
sudo update-rc.d ssh defaults

On a re-boot the ssh server will now be active. To make life easier on the pi you can follow this tutorial to not require a password.

Getting Started with EGL on the Raspberry pi

So i finally go my raspberry pi and my plan is to port my NGL library to it, the main difference is that NGL is using Qt and OpenGL 3.2 core profile and the pi will use OpenGL ES and EGL. Having never used EGL I decides to do a bit of rtfm and read the spec as well as some of the demo programs that come with the pi. The following is a basic introduction to getting started with EGL and using the pi in general. All the code for this post can be found here

EGL getting started

EGL is used as an interface between OpenGL (and other Khronos API's) and the base system (in this case the pi). It is responsible for accessing the display hardware and other synchronisation of the display / graphics context. In the case of the pi we use it to access the display hardware and use OpenGL or OpenVG with it.

All of the functions for this are stored in the header file  egl.h as shown below

#include <EGL/egl.h>

On the debian "squeeze" image of the OS these headers can be found in /opt/vc/include, we also need to add the EGL library to our build using the flags -L/opt/vc/lib -lEGL (more on this later in the Makefile section).

Accessing the display

Almost all the EGL functions require a valid display pointer to do their work, this is stored using the EGLDisplay typedef (it's actually a void * ).

We can get one of these using the following code

EGLDisplay display;
// get an EGL display connection
display = eglGetDisplay(EGL_DEFAULT_DISPLAY);
assert(display !=EGL_NO_DISPLAY);

If this is successful it should return a valid display, else the EGL_NO_DISPLAY value will be returned.

EGL initialisation 

Now we have a valid display connection we can initialise EGL and query what version we have, this is done with the following code.

// now lets initialise EGL and get the versions
int major;
int minor;
EGLBoolean result;

result = eglInitialize(display, &major, &minor);
assert(result != EGL_FALSE );
std::cout<<"Major version "<<major<<" minor "<<minor<<"\n";

On my version of the pi it gives the following output

Major version 1 minor 4

Configurations

Now we have initialised EGL we can query the different configurations available to use. This is done using the eglGetConfigs function which works in two different modes. The first mode will allow us to get how many configs there are, and the second will fill a buffer with all of the different configs. This is done in the the following code

EGLint numConfigs;
// first we call getConfigs with a NULL to see how many configs we have
result=eglGetConfigs(display,NULL,0,&numConfigs);
assert(result != EGL_FALSE );
std::cout<< "number of configs found "<<numConfigs<<"\n";
// now we create a buffer to store all our configs
EGLConfig *configs = new EGLConfig[numConfigs];
// and copy them into our buffer (don't forget to delete once done)
result=eglGetConfigs(display,configs,numConfigs,&numConfigs);
assert(result != EGL_FALSE );

......

// don't forget to delete once done
delete [] configs;

We can now gather the information from each of the configs using the eglGetConfigAttrib function. This requires you to pass in the attribute you wish to query and will return the value if set. The following code queries the attributes available on the pi (some that are in the spec are not on the pi)

for(int i=0; i<numConfigs; ++i)
{
 std::cout<<"Config #"<<i<<"\n";
 eglGetConfigAttrib(display,configs[i],EGL_BUFFER_SIZE,&value);
 std::cout<<"Buffer Size "<<value<<"\n";
 eglGetConfigAttrib(display,configs[i],EGL_RED_SIZE,&value);
 std::cout<<"Red Size "<<value<<"\n";
 eglGetConfigAttrib(display,configs[i],EGL_GREEN_SIZE,&value);
 std::cout<<"Green Size "<<value<<"\n";
 eglGetConfigAttrib(display,configs[i],EGL_BLUE_SIZE,&value);
 std::cout<<"Blue Size "<<value<<"\n";
 eglGetConfigAttrib(display,configs[i],EGL_ALPHA_SIZE,&value);
 std::cout<<"Alpha Size "<<value<<"\n";
 eglGetConfigAttrib(display,configs[i],EGL_CONFIG_CAVEAT,&value);
 switch(value)
 {
  case  EGL_NONE : std::cout<<"EGL_CONFIG_CAVEAT EGL_NONE\n"; break;
  case  EGL_SLOW_CONFIG : std::cout<<"EGL_CONFIG_CAVEAT EGL_SLOW_CONFIG\n"; break;
 }
 eglGetConfigAttrib(display,configs[i],EGL_CONFIG_ID,&value);
 std::cout<<"Config ID "<<value<<"\n";

 eglGetConfigAttrib(display,configs[i],EGL_DEPTH_SIZE,&value);
 std::cout<<"Depth size "<<value<<"\n";

 eglGetConfigAttrib(display,configs[i],EGL_MAX_PBUFFER_WIDTH,&value);
 std::cout<<"Max pbuffer width "<<value<<"\n";
 eglGetConfigAttrib(display,configs[i],EGL_MAX_PBUFFER_HEIGHT,&value);
 std::cout<<"Max pbuffer height "<<value<<"\n";
 eglGetConfigAttrib(display,configs[i],EGL_MAX_PBUFFER_PIXELS,&value);
 std::cout<<"Max pbuffer pixels "<<value<<"\n";
 eglGetConfigAttrib(display,configs[i],EGL_NATIVE_RENDERABLE,&value);
 std::cout<<"Native renderable "<<std::string(value ? "true" : "false")<<"\n";
 eglGetConfigAttrib(display,configs[i],EGL_NATIVE_VISUAL_ID,&value);
 std::cout<<"Native visual ID "<<value<<"\n";
 eglGetConfigAttrib(display,configs[i],EGL_NATIVE_VISUAL_TYPE,&value);
 std::cout<<"Native visual type "<<value<<"\n";
 eglGetConfigAttrib(display,configs[i],EGL_SAMPLE_BUFFERS,&value);
 std::cout<<"Sample Buffers "<<value<<"\n";
 eglGetConfigAttrib(display,configs[i],EGL_SAMPLES,&value);
 std::cout<<"Samples "<<value<<"\n";
 eglGetConfigAttrib(display,configs[i],EGL_SURFACE_TYPE,&value);
 std::cout<<"Surface type "<<value<<"\n";
 eglGetConfigAttrib(display,configs[i],EGL_TRANSPARENT_TYPE,&value);

}

This give a sample output like this (a full listing can be seen here or in the file output.txt in the code bundle)

Config #0
Buffer Size 32
Red Size 8
Green Size 8
Blue Size 8
Alpha Size 8
EGL_CONFIG_CAVEAT EGL_NONE
Config ID 1
Depth size 24
Max pbuffer width 2048
Max pbuffer height 2048
Max pbuffer pixels 4194304
Native renderable true
Native visual ID 37928
Native visual type 12344
Sample Buffers 0
Samples 0
Surface type 1639

Makefile

To build the program the following makefile was used, it includes the correct paths and libs

CC=g++
CFLAGS=-c -Wall -O3 -I/usr/local/include -I/opt/vc/include -Iinclude/ngl -Isrc/ngl -Isrc/shaders -DNGL_DEBUG
LDFLAGS=-L/opt/vc/lib -lEGL
SOURCES=$(shell find ./ -name *.cpp)
OBJECTS=$(SOURCES:%.cpp=%.o)
EXECUTABLE=EGLgetConfig

all: $(SOURCES) $(EXECUTABLE)

$(EXECUTABLE): $(OBJECTS)
 $(CC) $(LDFLAGS) $(OBJECTS) -o $@

.cpp.o:
 $(CC) $(CFLAGS) $< -o $@

clean :
 rm -f *.o $(EXECUTABLE)

That it for now but here is a sneak preview of NGL almost working

Using the Maya API with Qt Creator

I've just started writing next terms Maya API lectures and decided it would be a good idea to use Qt Creator as the ide for development as it's our main IDE. It also has the advantage of automatically creating the make file required for the projects and helping to make multi platform builds easier to manage.

Qt Creator Project file

qmake and Qt Creator both use the .pro file for the projects. In this case I'm going to create builds for both Linux 64bit and Mac OSX. qmake uses the pre-fix values linux-g+-64 for all flags relating to linux 64 bit and macx for Mac OSX. 

The following .pro file shows how this is done.

# This file is split into Three sections
# The first configures Qt and the source files for all platforms
# The second is the linux build
# The third the mac build
# (if your using windows you will need to add a fourth one!)
# first lets remove Qt core and gui not going to need it
QT       -= core gui
# set the variable for the Maya Location, this will be different depending
# upon the platform / version of maya used
TARGET = HelloMaya
# for for mac we need a bundle so change the name
macx:TARGET=HelloMaya.bundle
# here we add the source files (and headers if required)
SOURCES+=HelloMaya.cpp
# these are defines required by Maya to re-define some C++
# stuff, we will add some more later to tell what platform
# we are on as well
DEFINES+=REQUIRE_IOSTREAM \
         _BOOL
# These are the maya libs we need to link to, this will change depending
# upon which maya framework we use, just add them to the end of
# this list as required and they will be added to the build
MAYALIBS=-lOpenMaya \
        -lFoundation

# now tell linux we need to build a lib
linux-g++-64:TEMPLATE = lib

# this tells qmake where maya is
linux-g++-64:MAYALOCATION=/usr/autodesk/maya2011-x64/
# under linux we need to use the version of g++ used to build maya
# in this case g++412
linux-g++-64:QMAKE_CXX = g++412
# set the include path for linux
linux-g++-64:INCLUDEPATH += $$MAYALOCATION/include \
                        /usr/X11R6/include
# set which libs we need to include
linux-g++-64:LIBS += -L$$MAYALOCATION/lib \
                   $$MAYALIBS
# tell maya we're building for linux
linux:DEFINES+=linux

# tell maya we're building for Mac
macx:DEFINES+=OSMac_
macx:MAYALOCATION=/Applications/Autodesk/maya2011
macx:CONFIG -= app_bundle
macx:INCLUDEPATH+=$$MAYALOCATION/devkit/include
# under mac we need to build a bundle, to do this use
# the -bundle flag but we also need to not use -dynamic lib so
# remove this
macx:LIBS +=-bundle
mac:LIBS -=-dynamiclib

macx:LIBS += -L$$MAYALOCATION/Maya.app/Contents/MacOS \
             $$MAYALIBS

There are several sections to the .pro file above, mainly these are to make it easier to add to the project when needed. The two main distinctions between the linux and the Mac OSX version are how the plugin should be generated. Under linux the plugin is a normal shared object file (.so), however the mac version requires a bundle. To do this the -bundle flag is used and we also need to ensure that the extension .bundle is added to the Target.

Finally we need to add some defines to the build, depending upon the platform we need to either use -DOSMac_ or -Dlinux as well as the two flags REQUIRE_IOSTREAM which includes the correct iostream library for using std::cout and _BOOL to re-define bool.

Test Program
The following test program will send a message to both the shell maya was run from and the maya command window.

#include <maya/MSimple.h>
#include <maya/MIOStream.h>
#include <maya/MGlobal.h>

// This is a macro to create a simple command
// the compiler expands it to a bunch of code

DeclareSimpleCommand( HelloMaya , "NCCA", "Maya 2011"); 

MStatus HelloMaya::doIt( const MArgList& )
{
  std::cout<<"This should come from the shell\n";
  MGlobal::displayInfo("Hello Maya in the maya command shell");
  return MS::kSuccess;
}

Once this program is build depending upon the platform there should be a plugin ready to load in the maya plugin manager. The image below show this and the info set from the Command above

We now have two options to execute the loaded command. In the mel window we can invoke the command as follows, For the mel version

And for the python version we need to import the maya.cmds module first.

Using Flex with Qt

I've got a large project to work on which will require quite a bit of parsing / scanning of files so I've decided to teach myself flex and bison. So far I've read the first chapter of the excellent book Flex and Bison and the first example is as follows

/* from the flex and bison book do a word count */

%{
int chars=0;
int words=0;
int lines=0;
%}

%%

[a-zA-Z]+ { words++; chars += strlen(yytext); }
\n    { chars++; lines++; }
.     { chars++; }

%%
int main(int argc, char **argv)
{
  yylex();
  printf("Word count %8d %8d %8d\n",lines,words,chars);
  return 0;
}

To build and compile this we use the following command line

flex -o wc.c wc.l
gcc -o WordCount wc.c -lfl

This works fine, but as I use QtCreator as my ide I really want to configure Qt to do this all for me. QtCreator does have some limited lex and yacc support however I really wanted to use flex and bison, so need to add my own compiler to the qmake build system via the Qt project. To do this we use the QMAKE_EXTRA_COMPILERS flag in the project and build our own compile chain, the following extract shows how this works

# the is the name of the exe we want
TARGET=WordCount
# this is the source fed to the flex syste
FLEXSOURCES+=wc.l
# we then add this to the other files for editing
OTHER_FILES+=$$FLEXSOURCES

###########################################################################################
# now we are going to create a Qt compiler ojbect for the EXTRA_COMPILERS FLAG
# this basically has a number of attributes which we need to set as outlined below
###########################################################################################
# this flag list the sources we wish to input to this custom compiler, in this case listed above
# in the FLEXSOURCES variable
flex.input = FLEXSOURCES
# now we need to say what files to output, for flex we want to create the .c
flex.output = ${QMAKE_FILE_BASE}.c
# this is the actual compile command we wish to call in this case it wil be
# flex -o (output).c input.l
flex.commands = flex  -o ${QMAKE_FILE_IN_BASE}.c ${QMAKE_FILE_IN}
# once this compiler has been run we need to add the output files to the linker stage in this case
# as we are generating .c files we just add it to the SOURCES variable and it will be compiled
flex.variable_out = SOURCES
# this flag ensures that the extra compiler is run before the main c one (as we need to have the .c files
# generated by flex before we use the gcc compiler)
flex.CONFIG += target_predeps
# this tells the make clean command what files to remove
flex.clean =  ${QMAKE_FILE_IN_BASE}.c
# this is just the name of the extra compiler used in the make file (make flex for example)
flex.name = flex
# finally add this to the qmake project so it will have the makefile generated
QMAKE_EXTRA_COMPILERS += flex
# we need the fl lib for flex
LIBS+=-lfl
# tell qt we usign gcc
QMAKE_LINK=gcc
# this just cleans out some things for mac
CONFIG += console
CONFIG -= app_bundle

And that is about it, now I've got to read the rest of the book, but at least it makes the coding easier!

Setting OpenGL Formats in Qt

Got asked how to enable multi-sampling in my demos the other day, and realised that I hadn't shared this information in any of my lectures so I thought I would write it up here.

OpenGL has a number of extensions which allow a number of different rendering features to be enabled. For example we can do stereo, accumulation  multisampling and much more.

In Qt we do this by using the QGLFormat class and we can enable it for a specific QGLWidget, or for all widgets we create. For this example I will generate a default format and then create a widget to use the format. This code would be put in main.cpp in my demos (will update them soon) before the creation of the MainWindow class.

QGLFormat glf = QGLFormat::defaultFormat();
glf.setSampleBuffers(true);
glf.setSamples(4);
QGLFormat::setDefaultFormat(glf);

Now when we create the GLWindow in the ngl:: demos this will be used for all windows created. Finally we need to enable GL_MULTISAMPLE when rendering which can be done using the following code

glEnable(GL_MULTISAMPLE);

This method can also be used to enable things such as the new OpenGL core profile (under linux and windows for Qt 4.7 and with Qt 4.8 this will also work on the mac eventually, as long as you have Lion). You should be able to see from the documentation all the other features which can be enabled in this way.