On the second day, this homepage gets it’s first content update on the march towards the whole theory of a volume renderer with LOD:
The very first density function has now an article. It’s the classic discrete grid being used in the original Marching Cubes paper for example. And the terrain sample of OGREs volume component uses it, too.
The article contains quite a lot of formulas, but don’t let that scare you away, they are all pretty simple on their own.