I just found some problems running the castle demo...
This is the first:

When the demo starts, the trees are transparent... and they take quite a while to become fully "solid"... is that intentional?
The second concerns the "transition effect":

This is what I'm seeing from the distance... but if I get closer, instead of a smooth transition, the "sprite tree" fades away - then I see nothing - then the "tree model" starts fading in.
Also the "tree model" I see is completly different from the "sprite tree", see the picture below, from the same tree, just a bit closer:

Maybe if you fade out the 2D tree and fade in the 3D tree at the same time, you could get away with it...
This is the first:

When the demo starts, the trees are transparent... and they take quite a while to become fully "solid"... is that intentional?
The second concerns the "transition effect":

This is what I'm seeing from the distance... but if I get closer, instead of a smooth transition, the "sprite tree" fades away - then I see nothing - then the "tree model" starts fading in.
Also the "tree model" I see is completly different from the "sprite tree", see the picture below, from the same tree, just a bit closer:

Maybe if you fade out the 2D tree and fade in the 3D tree at the same time, you could get away with it...