Hi Steve,

thats' a really cool and amazing visualization solution based on WPF. I'm also experimenting with WPF and VirtualEarth to achieve some results like your application does it. But I'm still new in wpf. 

In my application I build a map, that contains particular tiles from Virtual Earth. This map is placed in 3D space. For the moment it's only a plane and not a sphere. 

Waht I'm really intersted in is what VisualTree (XAML) modell did you choosed to implement texturing with VirtualEarth tiles. 
For the moment I do this on this way:

  ViewPort3D
         |
      MV3D ( ModelVisual3D  my scene)
         |
      MV3D ... n (it's my map and other 3D Objects)
         |
      M3DG(Model3DGroup)
        /\
       /  \
M3DG  M3DG ... n (tiles of the map, for example 8x8 tiles)
   |          |
G3DM   G3DM      (GeometryModel3D - each of them consists
    |         |                            2Triangles => rectangle)
Material Material  (ImageBrush with VirtualEarth image)

I hope you can understand my Visual Tree model Wink.
After a VirtualEarth tile was downloaded, a GeometryModel3D will be textured with it -> Material with ImageBrush.    

So, but this way seems to be a very inconvinient for the performance. You do this with a sphere and it seems to run very fast. I know it's very hardware dependend, but it would be very interessting for me to learn on which way you do this?

I'm impressed of your work with WPF!