Wednesday, 21 March 2012

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
# here we add the source files (and headers if required)
# 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
# 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 \

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

# this tells qmake where maya is
# 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 += $$MAYALOCATION/include \
# set which libs we need to include
linux-g++-64:LIBS += -L$$MAYALOCATION/lib \
# tell maya we're building for linux

# tell maya we're building for Mac
macx:CONFIG -= app_bundle
# 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

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.