Fog of war always adds tonnes of great little quirks to games. There could be a way to make fog of war in the game in a way that would make it harder to see that precious ore through the wall, or so you can build your own super secret base hidden under tree stump so your friends can't get that previously mentioned ore. If you've ever played "Men of War: Assault Squad" they have a great fog of war system. In their system the units actually have a cone of vision and you can't see behind you, when you look at say a building it reveals to you so you can now see it. You look away, and it get's blown up, until you look at it again it still appears well "Un-blownup". Before you go "Men of War is an rts and this is side scrolling, silly." let me get to my point. What if the players had cones of vision and can see say like 140 degrees in front of them. Solid blocks block vision so that you can only see the block on the surface. This would make it so that simply lighting a room doesn't allow you to see into it from the outside. You actually have to walk in to see that brilliant interior design. Semi solid blocks like liquid or water could allow vision to be seen through up to a certain point, maybe like 15 blocks or so. When you look at something say a room you will from now on be able to see maybe like a greyed out version even when you don't look at it. However if an angry monster were to (hypothetically) come in to your house and trash the place while you were gone. Until you got sight on the inside it would appear to be normal from your characters "Memory". Once you get sight you see the horror that the monster inflicted on the place. And that new image gets put into your characters "Memory". And if you were to walk out, you would see a greyed out version of your trashed home instead. Now I'm not saying that the game is saving snapshots of moments that happens. It is simply hiding what is actually there until you look at it, with what you previously saw. As far as undiscovered things (anything that has never entered your characters sight) it could just simply be black. I realize it might make the surface look a little ugly what with being covered in black until you see it, so I'm at a loss for that. Players (and their names if they float above their heads) monsters and other "NPCs" would be hidden no matter what until you have sight on them. And you wouldn't see frozen greyed out version, they simply won't appear until you have sight. This would add more fear into going into caves (giant monster creeping up behind you). And also would allow players to create secret bases to hide in from other players. Vision is client side of course so you seeing something doesn't mean your friend sees it too. And just as a random suggestion to take it a step further. Hidden doors to create that special secret entrance to your beloved secret lair. They would blend into terrain or look like a random nature object but really be a door. Sorry for the paragraph style, really the best way for me to get my thoughts out.
I don't know, I just always hated how in Terraria, a light source from another room gave you sight into it. The game kind of already has a built in variant of what I described with the flashlight underground, but it still doesn't allow for hiding room or making it a little more difficult to explore underground.
I like this idea. Id rather you just have sight of everything on screen in proximity to you than a scope of vision though. I agree with woxandwarf that the field of vision would be a better mechanic suited to actual weather effects like fog. Of course everything behind solid substances (or blocks, whatever) should not be seen. This is the only way I can imagine stealth actually working for sneaky players and the only way to hide entrances to bases, or the bases themselves.
Fog of War has been around long before that. Warcraft, for instance, employed it. I know however there is lighting of war, essentially... below the surface, they show just that with the lighting demonstration. Now actual just fog generators would be interesting... a creepy zombie-laden ancient graveyard full of the walking dead planet..
Here, have a look at this. This idea is very similar, and I think you too would do good to butt heads, so to speak ^.^ http://community.playstarbound.com/index.php?threads/lights-line-of-sight.13167/
