CityGML and VC++

I need a 3D simulation of particles navigation using CityGML (City Goegraphic Modelling Language) and visual C++ 2010. simulation is already done in 2D, and i need it to be in 3D using CityGML for creating simulation enironnement. I have to simulate a part of a virtual City, with 3D environment and mouving particles ( citizen and vehicles), i want for this to use CityGML and VC , i want to have to possiblity either to run in 2D mode or in 3D, in the last case, environment elements ( walls, road .. shown in 2D mode by simples shapes)are stores in a database, and then are extracted to be used in 3D. the use of database is not mandatory, it's just for help, so if you can do without i don't have any problem.