Difficulty settings can alter the AI's detection capabilities based on their skill level. This can specifically affect how quickly they identify a threat and react.
It is important to note that this article only relates to content from the main ARMA games and does not detail how the AI detects the player's team in ArmA Tactics.
Third party-developed Creator DLCs, custom scenarios with scripted events, and unofficial community-created addons may not always consistently nor properly implement these forms of concealment, resulting in the appearance of inconsistencies with the AI's detection behaviour.
There may be instances where detection behaviours will differ depending on the game and after certain patches/platform updates. Where applicable, these will be noted and listed on the appropriate section (suffixed as having a caveat).
In a multiplayer environment, server performance can drastically affect the AI's detection speed and how they react to their surroundings.
This will be especially noticeable if the server is struggling to maintain performance for all clients. If the server in running in this poor state, AI-controlled units in a scenario may not detect or even react to being shot at by human players and/or other AI. To help mitigate this, servers can set up a headless client to offload AI calculations[1], thereby reducing the likelihood of the AI not being able to detect the enemy.
Due to its ongoing state of development, AI detection capabilities in ARMA Reforgerare not covered within the scope of this article.
There are two primary (but not exclusive) ways of how AI-controlled units are able to detect targets:
Detection based on model LODs[]
The majority of interactive and non-interactive objects throughout the series have sub-variations of their models referred to as a Level of Detail (or "LOD" for short).[2]
Top: Fully transparent block with a View Geometry LOD Bottom: Opaque wall without a View Geometry LOD
- Humans can see through the block above but the AI cannot - AI can see through the wall below but humans cannot (ArmA 3)
Specifically with regards to how AI detection is handled when it comes these objects, the View Geometry LOD within the model determines whether it can or cannot obstruct the AI from seeing through it.[3] Not all objects possess this LOD; those which lack one will allow the AI to see through them even if their visual appearance would suggest otherwise.
Detection not based on LODs[]
This method of detection is based on the speed of a unit's movement, their current stance, firing a weapon, or making themselves audible by performing certain actions. Unlike LOD-based detection, it is not based on the environment but rather on the unit's internal attributes which can dynamically change depending on their actions.
LOD-based detection[]
The following objects offer concealment against the AI based on their model's View Geometry LOD only:
A NATO and CSAT rifleman are positioned facing toward one another; neither can spot the other through the green smoke cloud (ArmA 3)
Smoke grenades (both thrown and launcher-fired) will disperse a thick cloud of smoke that conceals units inside and behind them from the AI.
Two CTRG and Viper fire teams are positioned facing one another; neither side can see through the multi-coloured smoke clouds (ArmA 3)
Once formed, a smoke cloud essentially acts as a temporary line-of-sight "blocker" that visually obscures their vision in that particular direction. There is no difference when it comes to colour; all colour varieties will provide the same degree of concealment against the AI.
However, it is important to note that the cloud/plume must be fully formed before it can properly conceal units behind or inside the smoke. Additionally, a gust of strong wind blowing constantly in a horizontal direction can prevent the smoke from forming properly. In the case of the latter, this will effectively make the smoke's concealment properties useless.
Lastly, smoke works both ways and can backfire against friendly forces, as smoke naturally does not distinguish between friendly and hostile AI. Both sides will not be able to see through the cloud/plume even if it is not intended to be used against the former.
Caveats:
Unlike in ArmA: Armed Assault and subsequent titles, ArmA: Cold War Assault is the only game in the series that does not have functional smoke grenades that block the AI's vision. They are only effective as a means of marking locations or obscuring the vision of human players (not AI).[4]
A U.S. rifleman remains hidden behind a bush from a Soviet machinegunner and rifleman (Cold War Assault)
Medium/large-sized bushes, trees with thick branches/leaves growing on them, and large plants, all obstruct the AI's vision and prevent them from seeing behind or inside the foliage.
However, it is important to note that not all foliage will fully conceal units hiding within them. Some are inconsistent in terms of concealment and may be deceptively bigger than their model would imply with regards to their actual View Geometry LOD.
Caveats:
Trees and foliage in ArmA: Cold War Assault do not consistently conceal against the AI. This particularly applies to some (but not all) forests and bush clusters on the Nogova and Everon terrains.
Running into foliage after being detected will not stop the AI from "seeing" and continuing to fire at the detected unit through foliage. However, it should be noted that this exclusively applies to ArmA: Cold War Assault and ArmA: Armed Assault only (it does not apply to ArmA 2/ArmA 3).
Top: A NATO anti-air fireteam is concealed by a "roof" made out of collapsed tin walls
Bottom-left: A CSATgunship is unable to see the NATO fireteam despite the four soldiers being in full view
Bottom-right: As soon as the NATO fireteam leaves the safety of the "roof", they are immediately spotted by the gunship and are fired upon (ArmA 3)
Hard terrain objects, such as walls or trees, will continue to block the AI's vision even after they have fallen over or collapsed onto their side due to being run over by a vehicle or blown up by explosives.
Top: A proneNATO soldier remains hidden by the fallen tree
Bottom: Two CSAT soldiers are ordered to move around the fallen trees; the NATO soldier is no longer concealed from the side and is immediately detected by the two soldiers (ArmA 3)
It is vital to note that while the View Geometry LOD's shape has not changed, its orientation will be affected. It may be necessary to switch stances to be properly concealed behind or underneath the fallen object. Additionally, it should be noted that since most objects will be half-sunk into the terrain, their Visual Geometry LODs still may not be large enough to fully block the AI's vision.
Centre-top: With the use of scripting commands to build a "wall" of Bergen Backpacks, the NATO (left) and CSAT (right) squads on both sides of the "wall" are unable to see each other
Centre-bottom: As soon as the NATO squad moves through the "wall" of backpacks, they are immediately fired upon by the CSAT squad since their vision is no longer obstructed by the backpacks (ArmA 3)
Backpacks placed or dropped onto the ground will obstruct the AI's vision. This is because the backpack models have a View Geometry LOD included as part of their model LODs.
However, their small sizes hinder their effectiveness as a form of concealment. In addition, because backpacks cannot be stacked atop one another without resorting to scripting commands, it will not be possible to see backpacks blocking the AI's vision in regular gameplay.
Non-LOD based detection[]
The following forms of concealment are not based on model LODs and specifically relate to how units move or interact with the environment:
A CSAT sniper wearing a jungle ghillie suit remains "invisible" to an entire squad of NATO soldiers despite being in the middle of a desert (ArmA 3)
Visual camouflage based on the texture of a uniform or unit's camouflage pattern has no effect upon AI units.
Wearing a ghillie suit or combat uniform intended for a forested/jungle environment in an arid terraindoes not affect the AI's detection capability. The sole deciding factor that determines whether they can see the target is their integral camouflage value, which is represented by a coefficient number.[5]
Note that despite not wearing a ghillie suit like the Rifleman, the Scout remains undetected by the Russian squad at distances below 200 metres (ArmA 2)
For instance, a USMC sniper in ArmA 2 possesses a camouflage coefficient of only 0.5.[6] This renders them much more difficult for the AI to see them from afar unless they walk within ~ 200-150 metres of the sniper. In contrast, a basic USMC rifleman has a significantly higher coefficient of 1.8[7], meaning that they can be seen from much further distances unless they switch stances (often well beyond 300 metres).
Caveats:
In ArmA 3, putting on a uniform that provides visual camouflage (e.g. Full Ghillies) will not lower the wearer's camouflage coefficient. This is because uniforms in ArmA 3 do not actually transfer the camouflage coefficient of the uniform onto the wearer. As a result, these types of uniforms offer no benefits to non-sniper/specops infantry classes (their visibility to the AI remains unchanged).
Likewise, snipers/specops infantry classes who decide to take off their camouflaged uniforms will not have their camouflage coefficient be affected by the outfit's removal. For example, a sniper who removes their ghillie suit and puts on a regular combat uniform will still retain a camouflage coefficient of 0.6[8] even though they are no longer wearing a ghillie. In contrast, the camouflage coefficient of a rifleman stays unchanged at 1.4[9] even after they don a ghillie suit.
Flashlights and other weapon-mounted torches will render the unit highly visible to the AI - particularly when they are activated under low-light conditions.
Despite wearing NVGs and flashlights being shone in their direction, none of the CSAT riflemen recognise the presence of the light beams. As a result, they do not turn around to face the NATO soldiers (ArmA 3)
However, it should be noted that the AI do not have the ability to "see" the flashlight's beam nor its spotlight. Activating a flashlight only increases the visibility of the flashlight's user. This is because flashlights do not actually emit a physical beam/spotlight that the AI can detect.
Three USMC grenadiers wielding flashlight-equipped carbines are forced to aim directly at the Russian rifleman with their flashlights activated; despite this, the Russian soldier is unable to see the flashlight's "beam" since the AI isn't looking in the direction of the grenadiers (ArmA 2)
As a result, if the AI are not actually facing in the direction of the flashlight's user, then they will ignore the light beam/spotlight that is being projected at or near them.
A proneU.S. Army SF recon operator remains undetected by the SLA squad even at less than ~ 200 metres (top), but is instantly spotted from beyond 300 metres once they sprint (Armed Assault)
A unit's stance and the speed of their movement (walking, running, sprinting, crawling) will affect their camouflage coefficient, regardless of whether they are being controlled by a human player or the AI.[10]
As an example, a NATO recon sharpshooter in ArmA 3 that is remaining completely still while staying prone will be very difficult for hostile AI to spot from afar - despite the fact that they are not equipped with a ghillie suit. Depending on the AI's skill level, they will need to get closer in order to detect the sharpshooter.
However, if the sharpshooter switches to a crouching stance and begins running while crouching, they can now be easily detected by the AI from a much greater distance (often in excess of ~ 250 metres).
Loud actions such as sprinting or walking upright while close to an AI will cause them to immediately react/look in the direction of the sound.[11]
Firing a weapon, even when suppressed, does not completely prevent the AI from hearing the shot. A suppressor will only reduce the range at which they can hear the shot; it does not eliminate the noise altogether. Continuing to fire shots without pause will eventually result in the AI looking for the source of the incoming fire and identifying the attacker (unless they relocate).
Additionally, beginning with ArmA 3, the AI can also hear and react to an AI or human-controlled unit's breathing as a result of fatigue. A fatigued unit will exhale loudly, which can be heard if they happen to be in close proximity to an enemy.
Myths[]
Common urban myths based on hyperboles and misconceptions associated with the AI's detection "capabilities" are as follows:
Six Soviet riflemen lacking NVGs are unable to spot the U.S. officer in total darkness (Cold War Assault)
The AI do not have the ability to see perfectly in darkness without night vision goggles.
Depending on the time of day, very dark lighting conditions with minimal moonlight or ambient artificial light (especially after 12:00 AM) will render the AI effectively "blind".
They rely exclusively on noise and proximity to detect under these conditions. This obviously does not apply if they are equipped with NVGs or the attacker exposes themselves by firing a weapon.
The AI do not have the ability to see behind them.
They must physically rotate their head in the direction of a potential threat in order to see them.
Due to having near-perfect peripheral vision (approximately 120 degrees) and AI in general always rotating their heads constantly, this can create the illusion that they can see behind them even though this is not actually the case.
A Russian rifleman walks past an entire squad of USMC Force Recon operatives; note how their heads are turned but their weapons are not raised, indicating both sides can hear the other across the wall but are unsure of whether they are friendly or hostile (ArmA 2)
The AI do not have the ability to see through walls or buildings.
Often, this is the result of a unit causing too much noise while operating close to an enemy AI.
The AI will naturally monitor the direction of the noise and switch to COMBAT mode upon visually confirming the source.
The AI do not have the ability to see through a terrain's landscape.
The terrain obstructs the vision of any and all AI. However, like walls and buildings, this does not prevent the AI from hearing footsteps or other noises.
A CSAT squad is unable to see the laser beam even at close range (ArmA 3)
The AI do not have the ability to see infrared laser beams.
Getting spotted by these beams is a misconception due to other external factors (i.e. the player was spotted moving by an NVG-equipped enemy).
An AI will not react to a laser beam even if it is shone directly in front of them.
The AI do not have the ability to see through coloured smoke clouds/plumes.
There is no difference in terms of concealment, no matter the variety of a smoke cloud/plume's colour.
A white smoke cloud/plume is not more effective at hiding a unit from the AI. It is identical to that of a red, green, blue, violet, orange or yellow smoke.
The AI do not have the ability to see through foliage.
Provided that a unit is concealed properly either behind or inside the foliage, the AI will never see them unless they are physically within proximity of it or the concealed unit fires their weapon.
In the case of ArmA: Cold War Assault/ArmA: Armed Assault, this will still apply so long as they have not been detected prior to entering the safety of the foliage.
