Far-away selection grids look bad

[zml2008]

(ok, yes, it's a subjective title... sorry)

But anyways, looking at a large selection, as grid lines get further away perspective makes them appear closer together, and before culling kicks in the lines already dominate the view.

The culling implementation is also fairly ugly -- it's a hard cutoff at 128 blocks away (and I think some issues with its math are why the selection grid can appear to move with the camera in some cases). If this culling can be replaced with some sort of exponential? spacing of grid lines i'd expect nicer results.