3D Nature: Leader in Virtual Globe Authoring
Virtual Globes are computer software for displaying and interacting with a 3D representation of the Earth (or other planets). Virtual globes are used for research, data visualization, and entertainment. The best-known Virtual Globes are Google Earth and NASA's WorldWind. A late-comer to the scene, ESRI's ArcGIS Explorer (not yet available), promises to take the field in a new direction, towards a heavy GIS focus.
Each tool offers different capabilities and has strengths and weaknesses. Google's product is available for Windows, Linux and Mac. WorldWind is currently Windows-only but may run on other platforms in the near future. As a commercial entity, Google has a large library of high-quality commercial imagery whereas WorldWind mostly relies on freely-available data. Google's terrain data is acknowledged to be quite coarse and indistinct compared to WorldWind. WorldWind is very extensible, whereas Google Earth is much more closed.
Both products allow for a certain amount of data extensibility for adding new imagery, boundaries, buildings and other structures. Google created the KML/KMZ and COLLADA file formats. WorldWind reads KML/KMZ, and also has its own formats. Notably, WorldWind can also add terrain, whereas Google is not designed to.
3D Nature makes Virtual Globe authoring tools (Scene Express for Visual Nature Studio and World Construction Set) that offer easy creation of add-on environments for both Google Earth and WorldWind. Create entire environments complete with textured buildings, 3D trees, draped imagery, viewpoints, and even terrain! Best of all, once a scene is built, it can be authored to any supported Virtual Globe, or other environments, making best use of the capabilities of each.
An overview of Scene Express' KML support and samples of Scene Express output for a variety of realtime landscape environments are available.