Qt3d Scene3D documentation seems to be incomplete

in https://doc.qt.io/qt-5/qml-qtquick-scene3d-scene3d.html#details

"If the scene to be rendered includes non-opaque materials, you may need to modify those materials with custom blend arguments in order for them to be rendered correctly. For example, if working with a PhongAlphaMaterial and a scene with an opaque clear color, you will likely want to add:"

But it never says what to add...