Hello!

I have infinite, not xstream, but just in case: Did you try to zoom out very far? The effect can be quite subtle depending on the size settings. If it worked  and you move the camera for example 100km up, you should see the horizon curve and the side view should also show a curve in the terrain.

By the way: You do need to use an infinite terrain or ground plane for this.

You could also activate the "Planet terrain" setting. In this case the terrain will form a complete sphere.

Sorry if you already knew this, but it confused me initially.

Ciao
TD