Before using each of the Qt 3D modules, you have to enable the module separately in the project file. For example, the following line will enable all currently documented modules:
QT += 3dcore 3drender 3dinput 3dlogic 3danimation \ qml quick 3dquick 3dquickextras 3dquickscene2d
When using QML, each module must also be separately imported:
import Qt3D.Core 2.10import Qt3D.Render 2.10import Qt3D.Extras 2.10import Qt3D.Input 2.0import Qt3D.Logic 2.0import QtQuick.Scene2D 2.9import QtQuick.Scene3D 2.0