What's the performance cost of it running on different levels?

A 3d model is made of polygons. The more polygons, the higher detail the model has. Tessellation is another form of LOD, which is Level Of Detail. Any game must have LOD in order to be optimized for performance. For example, it makes no sense to render a model consisting of 200k polygons from a distance it's barely visible from. While it's barely visible, it is still rendered and therefore, suck up performance. Therefore, a LOD technique is applied, where each model has a few variations, varying from a high polycount model to a low polycount model, and they're defined to appear in-game according to different distances from the player's object (eg, our aircraft). So, now that you understand the traditional LOD technique, you can go on to figuring out tessellation (technique implemented in dx11+). Tessellation takes a 3d model and increases it's polycount on-the-fly, meaning in real-time rendering. The difference between traditional LOD and tessellation is, that LOD is done by pre-made models which only switch in-game, namely, do not change their polycount. It's easy to watch how tessellation works, by setting wind to 36kts and flying low above water. The higher the tessellation, the more defined/detailed the waves will look. In a nutshell, that's what tessellation does. Ofc, you can google and learn more about this rather important feature.

Thanks maybe well get this someday

http://m.youtube.com/watch?v=4G9anRoYGko

I believe that's the kind of water P3D is based on.

So I do see the waves now but the simobject does not actually float on the waves...  even get's swallowed whole by the waves lol

 

Well at least it's a start!