knowsAbout

Operation Flashpoint: Resistance v1.91

• As soon as An AI unit gets hit with a bullet his knowsAbout level for the unit that shot him will instantly jump to 1.5, even if the shooter is 1000m away. Vice versa is also true. If An AI soldier's knowsAbout level for an enemy is 0.7 and the soldier fires and hits the enemy, his knowsAbout level about the enemy will instantly jump to 1.5.
• Some editors have found, whilst using this command over the years, that the following characteristics have cropped up:
  • AI enemies have a very limited amount of peripheral vision, it is not nearly as good as a human player's. A target must be in front of the unit for him to be noticed, so if you sprint right behind an enemy, this value doesn't increase.
  • Depending on the unit's skill level, it can take a little time for the unit to notice a target. So if you run right past a unit, this value might not increase.
  • Bushes between the unit and the target seem to have little effect on this value, and trees definitely have no effect. You may be in a forest and can't see the unit, but he can see you.

the magic knowsAbout number is 0.105 It's not that simple. Maybe true for infantry but not all vehicles:

Reveal command sets knowsAbout to 1, but planes still won't fire at soldiers on the ground. There's only one known way to pass through this - designate target with another fake infantry unit near the target. As soon as this fake unit see the target knowsAbout lifts up to 2.5-4 and even single enemy soldiers are attacked from the air (of course if plane has suitable munition :))

According to Suma:

All friendly units within a view distance to each unit [are revealed (to the player? or each friendly?)] on the mission start. The code is half broken, as it does not make the units known, it only sets the "accuracy" value for them.

Note: This is not affecting enemy units at all.

Arma 2: Operation Arrowhead v1.62 infantry tests: It is still true that the command returns values between 0 (lowest) and 4 (most). Freshly Spotted units will have at least 1.5, slowly decreasing when the target disappeared. The following table shows my test results on a clear day in Takistan using the Vector. Please note that the returned values vary considerably depending on weather and time. Moonlight however seems to not have any considerable effect.

Arma 3 v1.82 knowsAbout tests, player moving towards enemy AI, facing each other:

Code used (click on "Expand" to the right):

player allowDamage false;
player enableFatigue false;

player setPosATL [0,0,0];
player setDir 0;
unit setPosATL [0,500,0];
unit setDir 180;

waitUntil { speed player > 0 };

[unit, player] spawn {
    params ["_unit1", "_unit2"];
    private _time = time;
    private _knowsAboutData = [
        format ["world = %1\ndate = %2\nanim = %3\nweapon/scope = %4/%5\nskill/rank = %6/%7\nplayerType = %8",
            worldName,
            date,
            animationState player,
            primaryWeapon _unit1,
            (_unit1 weaponAccessories primaryWeapon _unit1) select 2,
            skill _unit1,
            rank _unit1,
            typeOf _unit2
        ]
    ];
    private "_knowsAbout";
    private "_entry";
    while { alive _unit1 && alive _unit2 } do
    {
        _knowsAbout = _unit1 knowsAbout _unit2;
        _entry = [_unit1 distance _unit2, _knowsAbout];
        _knowsAboutData pushBack _entry;
        systemChat format ["time: %1 - %2", round (time - _time), _entry];
        copyToClipboard str _knowsAboutData;
        sleep 1;
    };
};

As of at least Arma 3 v2.04, all sides appear to always perfectly know about props (knowsAbout of 4) unless they are beyond max view distance. Direction of the observer, distance between observer and object (excluding those which are beyond the max view distance) and amount of obstructions between them do not seem to affect it. However, there is a short ~0.5 second delay after mission start before units perfectly know about props.

In addition, props appear to always have a knowsAbout value of 0 regardless of side or other object checked, including other props.