Planetary scale rendering is a fairly popular topic and and to do it right requires paying attention to such things as:
- Floating point precision.
- Difficulties of rendering spherically.
- Data paging the enormous amount of data required to cover the global surface area.
There are plenty of examples of some pretty impressive work. Here are some of my favourites:
First off there is Eric Bruneton. His work with ocean rendering and more recently rendering massive amounts of trees makes for a pretty cool demonstration.
Then there is Outerra that does global rendering very well. You’ll notice that it is capable of rendering roads that are centimetres high on a globally scaled system. It also utilises fully asynchronous loading of terrain data that is then complimented by fractal manipulation of the terrain data.
Finally the developments over at Procedural World offer an alternative method to traditional rendering techniques by instead representing and rendering the world using voxels (think Minecraft, but even smaller cubes).