i can confirm this observation on R9 280X AMD ... doubt its GPU related, but its noticeable.
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From what I can tell it seems to be more related to the size of large ice covered asteroids, all the transparent blocks seem to be causing a graphic strain.
The reason the fps goes up as you get closer is due to some asteroids no longer being in your field of view, however asteroids behind the one you are looking at will still cause an fps drop.
https://youtu.be/9DOh73wpfg4
Only thing I can figure to help this out is have transparent blocks go opaque after a certain distance