Like in this scene here, taken from the Blender gallery - There are shadows on the floor, yet it seems to continue forever into the background - How is that achieved?
One of the things that you can easily achieve in CG, which you cannot achieve easily with real-film, is absolutely even lighting over an arbitrarily-large surface.
Furthermore, you can have things which simply do not exist in the real world: - Lights that cast shadows instead of light. - Lights that can shine right “through” an object that they have been programmed not to “see.”
It’s an old studio photographer’s trick that’s been around forever. 3D artists just adopted the trick from them. Papasurf is correct, it just bends upwards in the background so there’s no line/crease to see.