It's line of sight rules. I've played enough different games that I can safely tell you that any set of line of sight rules will lead to "arguing and BS". Especially if you're used to a different set of rules. All line of sight rules end up being arbitrary and capricious. That's just how it is. I mean, this is how many years in the future, and the Combined Army remotes have the same vision limitations as some human's G:Sync robot. How is that realistic? And why aren't these advanced, well trained troopers turning around when someone gets within their zone of control? In this game, troopers have 180 degree front arcs. In Malifaux, they don't. In Warmachine/Hordes, they do. In Warmachine/Hordes, the line of sight rules aren't quite the same as the current Errata line of sight rules. In Warmachine/Hordes, the green trooper can't see the blue trooper because of the corner (because of a difference in one sentence). In Malifaux, there's no facing so the blue and green troopers can see each other. Three different games, three different results whether the models around a corner can see each other.
Disclaimer: Morat Rules Lawyer. Best thing I can suggest for line of sight rules is immediate pre-emptive strike to kill** the opposition. Diplomatic Counsel suggests I translate that again... Print out the errata page with its four diagrams, and point out the differences. I'm in your front arc. You ARE NOT in my front arc. I DO NOT get to shoot* back. I'm in your front arc. You ARE in my front arc. I DO get to shoot* back. ** See Goguernar Gorecannon. * Dodge, shoot, shoot back, etc.
It's important to remember that the Green trooper has reciprocal line of fire. In a static situation where the Green trooper is not observed (such as the Blue trooper not facing the Green and not declaring a movement (and as such doesn't have 360 vision and no vision to Green)) the Green trooper will not have line of fire. Basically, the Green trooper can't see around that corner, they can only see enemy troopers (or objects that are treated like troopers, i.e. perimeter weapons, holoechoes...) that can see the Green trooper. "See" not necessarily "shoot" it's enough Green is seen to be reciprocal.
Please note that reciprocal LoF is not involved in any way in the diagrams. Green has LoF because blue is at least partially in their front arc (obstacles are irrelevant for this bit), and there is an unobstructed LoF from part of their Silhouette to part of blue’s Silhouette.
The confusion stems from "Line of Sight / Line of Fire" being the only requirement to fire back at each other in most games. In Infinity, especially after this FAQ, there's a very strong distinction between: "Can I trace a line between any part of our bases?" (Line of Fire), which is the basic requirement to even consider shooting at each other, but it is not enough! This Line of Fire only means "we can see each other"; and: "Am I turned towards you far enough to be able to turn my weapon and fire at you? Are you not completely behind my back?", which is shown by the 180° Facing line; Line of Fire ("can we even see each other") can be blocked by terrain, walls, etc., bases / silhouettes need to be able to "see" each other to fire at all. There is no such limitation for Facing, that's just "checking if you're in my back half and I can't fire or at least a bit in my front half and I can fire". In the 2nd image, the Blue and the Green guys' bases can "see" each other (the orange LoF line). The Blue guy is a little bit in the Green's front arc, as shown by the red thin line. This means Green is turned towards him far enough that he can return fire along that base-to-base LoF we checked before. The wall is irrelevant for Facing.
I find the second bullet point kinda ambigious? At first i was wondering why green model has the LoF, so i went trough the errata - has a model in his front arc? Checked. Can draw a line between their bases? Checked. " 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)." Since arc indicates what the trooper can see, then it means that the 3x3mm part he sees is the one in his front arc, behind the obstacle, right? Or is it the 3x3 part to which he has the between-bases line? That would mean the reason for which he has no aro in the first picture would be just because of the arc, but arc is what indicates what he sees. So if i am right with the first version, would it just mean that you need to have 3x3mm of the targets volume in your front arc? And ofc the line between bases?
Not in the example posted in this thread, no. LOS works in two separate clauses now: 1) Is the model in my front 180 arc? (Ignore everything in between) 2) Can I draw a line from anywhere on my silhouette to anywhere on their silhouette? (Taking terrain and other models into consideration) If the answer to both of these questions is yes, then yes, you have LOS.
Because in that case blue is not firing in the back, he should have moved a bit further to get his base (silhouette) out of green front arc.
I am shooting a model and I am in the models front arc. The model may shoot me back. I am shooting a model and I am in the models rear arc. The model may not shoot me ( unless he has 360, SSL2 etc.) Once you realise you just worry about arcs not which specific part of the base you see, this ruling is infact quicker, easier and leads to less explotiation. Under this ruling it avoids the shenanigans with superjumping just high enough to see the rear of the base before you see the front. This is an improvement.
Okay, so in the pic, if the blue moved a bit more forward, green could not shoot him, because he would be out of his front arc(despite being more out of cover)?
Shooting models in the rear is still core to the game. You just cant Geometry it to shoot them in the back from the front now.
If blue were already a bit forward for the entirety of the order, yes, that would be correct (I am just nitpicking the use of the word "move" here), just as the other graphic in that part of the Errata indicates:
Aaaah, okay, wasn't aware you could do it before. But if for example it started it's order a bit back or even at the same place, then did move a bit forward - shoot, then it would be considered that he is visible, because at one point during the order he was visible(in front arc, despite models front arc actually not being able to see him) either though later on he is not?
Correct, that fundamental part of Infinity has not changed. You have always been able to ARO shoot a model that began its movement, or conducted part of its movement in LOS of an opponent and then left it by the end of their movement, either by moving behind a piece of scenery or completely past their front arc.