New rules of Ceberus aren't clear.

1. Look at the battlefield from above, as if it were only two dimensions. Attempt to trace
an imaginary line from the dot in the activated unit’s space to the dot in the target
unit’s space, just as described in the Revised Core Set. If line of sight would be clear
in 2D, without thinking about height, then line of site is clear in 3D. If line of sight
would not be clear, continue to step 2

2. If the unit on the lower level is directly behind the object that would block 2D line
of sight, then line of sight is blocked in 3D, no matter how high up the other unit is.
However, if the unit on the lower level is not directly behind the obstacle that would
block 2D line of sight, then line of sight is clear between the unit on the lower level
and the unit on the higher level.

Is this LOS?

flic.kr/p/b9Udkx

flic.kr/p/b9Udqz

What about this?

No for both in either direction, from outside you can only see in to the entrance square and from inside you can only see out from an entrance square.
(see page 14 in operation Cerberus.)

Can you explane why? I have read over the rules and don't see a diffent answer. If you are on the roof you are in the open.

I should say according to the rules both units are consider outside.

If a squad is on the roof of a structure, it is considered to be outside of that
structure.

If both units are outside the structure then they have LOS.

No, they don't. Consider the rules you noted.

1) Look at the battlefield from above as if in 2D. The building space between the two spaces would block line of sight in 2D.

2) Continuing to the second stipulation, the lower unit is directly next to the terrain that would block line of sight in 2D, and so line of sight is blocked.

It does not matter if the upper unit is in the building, or on the roof, because the second stipulation only concerns itself with whether the lower unit is next to terrain that could block line of sight from a 2D perspective. If the unit were inside the building, the standard building rules would block line of sight.

If the upper unit were on the roof, and the lower unit were back away from the structure, they would still not have line of sight, because the building space between them is as tall as the space the upper unit is in, and so they would have no angle down to the ground. If you were on the Western edge of a large (multi-space) building with a flat roof looking East, you would not be able to effectively see the ground without having something else to climb up on. Oddly enough, the same blocking effect would hold true if the building space between the units were higher than the upper unit, as well. They did not stipulate that in the rules as it is common sense, but common sense is sometimes missing when people are trying to read rules. A unit could not see through terrain that is as tall or taller than the higher unit to see another unit at a lower elevation simply due to the inability of light to bend sufficiently to wrap around obstacles.

A small (one space) building (or the facing side of a larger building) would allow someone standing on the roof to see people on the ground below them, or standing some distance behind a large vehicle between the two groups without the vehicle being too close to the lower unit (the one space behind stipulation). If they were directly behind the vehicle, line of sight would again be blocked regardless of the elevation of the higher unit.

The line of sight rules for different elevations only apply if there is a possibility line of sight might exist. That means there has to be the possibility of a straight line between the two units. If there is blocking terrain as high or higher than the highest unit between the two, there is no such physical possibility.

OptimusPrime21 said:

No, Gimp's post would put my explanation to shame.
+1 to Gimp.