[infogulch]

There's a problem with that I think. If I understand correctly, the inside-a-chunk tests are filled directionless, so this wouldn't work.

Basically it performs a flood fill on contiguous groups of all the transparent blocks in the chunk. If any group touches two sides they are considered to be able to see each other. Keep in mind this is precomputed and doesn't have a "looking-at" direction.

Perhaps you could perform this test six times, one for each face. Then you would have a direction.

[Ogre]

Yeah, see my reply to myself, I beat you by a few minutes =) Whether 6X the searches is worth it or not is something only testing can answer, I think.