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.