LoF rules ssay this: "The troop must be able to see, at least, a part of the volume of its target with the size of the target's head, or a minimum size of approximately 3x3mm (the size of the black squares on the Silhouette Templates)." (emphasis mine) Now, I take that "or" as a clarification on what size that "target's head" is supposed to be, and that you either can see that 3mm by 3mm square on target's silhouette template, or you don't have LoF. Other people in my group, on the other hand, insist that if there's a spread out zone of the same size, that's still enough. Usually that disagreement is not really important... but for prone models, it is. Since a trooper in the Prone state has a silhouette equal to his base, his total height is exactly those 3 mm - and thus if he isn't exactly on the edge of a roof, then anyone looking up at him wouldn't be able to see that square => can't draw LoF to him. I.e. prone trooper that's away from edges can only be shot by someone whose silhouette rises at least 3mm higher than that roof; and a prone trooper on the edge that got shot from below and fails a Guts roll has to move away from that edge (and gain total cover). Is that correct?
Remember that LoF is reciprocal So if a sliver of the prone model's base can see 3x3mm of another trooper, then they have LoF to each other.
What if that sliver is outside of their front facing arc? What if a model can only see a sliver of the rear of the base? (say a tall model looking over cover at a prone model up against that cover)
Sure, the actual Line of Fire is there, the model facing the wrong way is just bound by the restrictions on what skills can be declared out of their rear facing.
as the FAQ had said : "A troop have a LoF angle of 180˚, that is, they can see with the front half of their base. LoF can be drawn from any point in the troop’s volume to any point in the target’s volume." but if you draw from your rear arc then you cannot ARO or as written by the FAQ : "In summary: For a miniature can ARO must be within its 180˚ front half base and be able to draw the LoF from those 180˚."
Ah. There's my problem - I remembered it the other way, as in that you have to be able to draw the line both ways to have LoF ("If I can't see you, then you can't see me". Well, not accounting for facing). But seeing the 3x3 square on at least one silhouette of the two is still required, right? Cannot substitute with 1x9 rectangle?
Correct, one trooper must be able to see at least 3x3mm on the other, 1x9mm is not valid (or any other iteration of 9 square mm). The reference in the rule to "the size of a head" harks back to the second edition LoF rules before Silhouettes existed. N3 codified this into being 3x3mm, meaning that the old Ko Dali model is no longer harder to get LoF to (she had a whopper of a noggin).