Map only showing area I can see

[lesander]

Hello there,

Yesterday, my map seems to have been reset (or I pressed some button I'm unaware of). The thing is, when I tried to re-explore the area around my base, something weird occurred: When exploring an area, the map only renders the bit I can see, eg: land behind hills don't get rendered, 'cause I'm behind the hills. Also, when I'm moving out of an area that I've discovered, the map unloads everything I can't see.

I've tried the Underground mode switch key "U", but that didn't seem to do it.

Help?