Werner:

SH3D is a program that is VERY actively being developed. However, there is just ONE developer: Emmanuel Puybaret. In the last six months the program has seen many new features, most of which in response to wishes from users.

The focus of the program has always been on ease of use and interior design. If your interest is more in the area of architecture, than there may be programs that offer more features. Maybe you have seen the multilevel tutorial, which offers a layer workaround.

Hans