what do i use for this? you see, there are 4 tur....mob..THINGS, roof, inside, area, and grass. there are walls making a square shape. let me make a diagram.

- wall
i inside area
ir inside area with roof thing on top
g grass
C chair, with inside area and roof on it

ggggggggggggggggggggggg
gggggggggggg ----------------- gggggg
ggggggggggggg-iriririririrCir- gggggggg
ggggggggggggg-iriririririririr- gggg
ggggggggggggg----------- -----

i want it so that when the player steps into the roof, the roof disappears and he can see anything vthats on the inside area, and anything thats not on the inside area is black. how can i do that?