I was at the 3D GeoInfo 2012 conference last week and I learned about the DB4GeO / DB3D open source geospatial database, which is a Java object-oriented database focusing on 3D data. It supports CityGML, has a RESTful API and has its own WebGL visualization tool.
Since I failed to find much about it on the web other than the GitHub page (it seems the code wasn't synchronized for a while), let me serve you the abstract [pdf] of last week's presentation: "The analysis of complex 3D data is a central task for many problems in the geo- and engineering sciences. Examples are the analysis of natural events such as mass movements and volcano eruptions as well as 3D city planning and the computation of 3D models from point cloud data generated by terrestrial laser scanning for 3D data analysis in various domains. The volume of these data is growing from year to year. However, there is no geo-database management system on the market yet that efficiently supports complex 3D mass data, although prototypical 3D geo-database management systems are ready to support such challenging 3D applications. In this contribution we describe how we reply to these requirements advancing DB4GeO, our 3D/4D geo-database architecture. The system architecture and support for geometric, topological and temporal data are presented in detail. Besides the new spatio-temporal object model, we introduce new ideas and implementations of DB4GeO such as the support of GML data and the new WebGL 3D interface. The latter enables the direct visualization of 3D database query results by a standard web browser without installing additional software. Examples for 3D database queries and their visualizations with the new WebGL interface are demonstrated. Finally, we give an outlook on our future work. Further extensions of DB4GeO and the support for the data management for collaborative subway track planning are discussed."
I'd like to see the differences between PostGIS vs DB4GeO features in regards to 3D geodata. Is DB4GeO more and a playground for researchers?