This process does not yet exclude large vertical cluttering
elements such as large cupboards from the potential wall patches.
We therefore perform a further pruning, following the intuition
that genuine wall structures must cover a vertical extent that is
almost equal to the distance between the floor and the ceiling.
Checking for this condition in real-world inputs such as 3D scans
of offices or apartments is problematic. Obstacles located between
the camera and the walls (see also Fig. 1, left) can severely limit the
amount of structure visible. Taking more scans from additional
viewpoints can only partially solve this problem and it cannot be
considered a viable solution for static 3D laser range scanning.