Why generate nonexistent region at the boundary of temporary graph?

It is possible that there are reflective furniture such as floor to ceiling windows and floor mirrors in the home, resulting in the non-existent area generated when the equipment is scanned and mapped.

If there is glass or black on the wall, the lidar can’t reflect normally, and virtual shadow will appear, which is normal. But it may also be caused by the map error. If the map error, the equipment will not be able to clean normally.