Hi Laurenz,
Sorry for my incomplete explanation, it seems the empty: true implies using SCS.
In order to start with an empty scene using streaming you can generate a webviewer using these parameters:
viewer = new Communicator.WebViewer({
containerId: “container”,
endpointUri: endpoint,
model: “_empty”,
rendererType: Communicator.RendererType.Client // exercise: specify client or server
});
viewer.start();
Hopefully with this you should be able to move forward and give it a try,