QT3D Scene to Pointcloud

[Cupras]

Hello,

I want to create a point cloud from a scene rendered with QT3D.
For this I need access to the framebuffer e.g. with glReadPixels. Or is there another possibility?
The only thing I found is to render the scene into an image, but that's not enough for me.
Is there a way or can I get to the OpenGL context to directly execute OpenGl commands?

Best regards,
Markus