Since I haven't been updating the my terrain library (AdVantage Terrain - silly name, isn't it?) for a while now and I'm probably not about to do so in the future, I've decided to close the web page and move everything here.
But not all is lost! In the meantime I've been working on a paper that describes an updated/modified version of the algorithm that inherits the quadtree organisation, but works directly on heightmaps (kind of like 'Geometry Clipmaps', but with more correct LOD distribution and smoother transitions between levels) - I'll update this web page with all the details as soon as it gets published. The paper will come with the full free-to-use source code and everything, so it practically makes AdVantage terrain library obsolete except in some rare scenarios.