Output QVector3D to QString

You can use QDebug::QDebug(QString*) and the operator << from QDebug :

QString str;
QDebug(&str) << QVector3D(1,2,3);

But because that constructor is not declared explicit, you can omit the QDebug:

QString str;
&str << QVector3D(1,2,3);

(I don't know if this is a bug or a feature, and if you can rely on that second form in future versions of Qt).