[Qt Quick 3D] Support dynamic scene creation in C++

Some customers use 3rd-party libraries (like Kitware VTK's mesh creation and filter classes, vtkPolydata, vtkAlgorithm, etc.) to generate meshes and scenes in C++, and they also dynamically update the relations between nodes. These libraries enable the developer to filter, alter, create points, vertices, faces for live rendering. Therefore handling meshes, images, point clouds in C++ are a requirement.

They want to be able simply pass the root node to QML and have the whole scene rendered.

• This was possible with Qt 3D, but that is now being sunsetted.
• Qt Quick 3D does offer QQuick3DGeometry as a C++ API to create and update geometries, but only for a single node.

Suggestion
Expose more C++ API for Qt Quick 3D, to allow developers to port from Qt 3D to Qt Quick 3D