This all reminds me of a problem I found some time ago, with patch 1.3, when raising the visibility to more than the stock 9000 yards. I placed the maximum visibility at 20000 yards with mini-tweaker, but the result was not good in that what got moved to 20000 yards was actually the horizon line
I did some tests and concluded that the visibility parameter in SH4 didn't work the same as in SH3. Seems that the physical horizon line -which for a fleet boat watching from the deck should be around 9000 yards moved to 20000, and thus ships did not show "under the horizon" effect until they reached that distance. :hmm: i.e. the hull, then superstructures, finally masts wouldn't get hidden by the horizon line until reaching the visibility limit, and then they would just fade into the horizon fog slightly after.
Theoretically, when watching from the bridge you should see any ship further than 9000 yards already "sinking" behind the horizon, and not be able to see the
full hull. Of course, at periscope depth through the scope you should see the effect even much closer, -as it is only a few feet above the water-, say 5000-6000 yards (Which actually made distance mesuring above that distance problematic in real life)
That has nothing to do with the actual maximum visibility, as you should be able to see a tall smoke column above the horizon even at periscope depth or sea level.
But seems that despite actual visibility being 20000 metres in SH4, the horizon line and the earth curvature effect are not perfectly displayed in SH4
