Why do we provide a Qt 4.8 version of ITK-SNAP?
Since release 3.2, ITK-SNAP is built using Qt5, a graphical interface platform. Qt5 requires a pretty good video card, and not all machines have them. Some users experience problems with 3D rendering not being displayed, or just blank windows. When we drop back to Qt4, most of these problems seem to go away. We are working on a more permanent fix, but for the time being, we are providing a compatibility version of ITK-SNAP 3.4 that is compiled against Qt4.
- For MacOS users, the drawback is that the Qt4 version does not take advantage of the higher-resolution Retina display. This is purely cosmetic. There are no known drawbacks for Linux and Windows users.
Problems with Running ITK-SNAP over X11, NoX and X2GO
When users try to run ITK-SNAP on a server (e.g., computing cluster front-end) with limited video card resources, errors arise. A typical error is
QXcbConnection: Failed to get the primary output of the screen
QXcbConnection: XCB error: 172 (Unknown), sequence: 158, resource id: 150, major code: 149
Qt developers are working on this issue. For the time being, we are providing a version of ITK-SNAP 3.4+ compiled against Qt 4.8. This version seems to work well when used over ssh X11 transport (ssh -X), x2go, NX and other remote desktop solutions. There are no real drawbacks compared to the Qt5-based builds other than slightly less pleasing visual look and feel.
