Until recently, "3D GIS" for most people meant the ability to plant buildings, trees etc. onto a 3D landscape to give a more realistic perspective view.
Efforts were then made (especially by the "CityGML" group) to add further levels of detail to the building facades.
However, more recently we have perceived a growing concern with the inclusion of building interiors in these models,
and that raises a variety of complex issues of the representation of the rooms themselves and their internal adjacency and connectivity.
While issues of this type have been addressed in part by the Computer Aided Design (CAD) community,
their needs are somewhat different and it is not obvious how to include their methods within a GIS environment.
As there are now several research groups asking questions of this type,
it seemed appropriate for us to help to provide a meeting point for those researchers working on this class of problems.
The "3D Topology Group" is a subset of ISPRS Commission II, Working Group 2 that aims to bring together those of us who are interested in the subject,
to provide a place to exchange ideas, and a web site where we can upload articles, software, etc. that might be of common interest.
We hope that this will be a useful endeavour, and we will meet many interesting people and ideas.
Please join our discussion group: 3D Topology Group