Many players feel that the AI detects them with robotic radar senses. Although the AI rely on hearing gunfire or footsteps and then turning to acquire targets visually, this process has a problem.
The following is my longstanding observation on how the AI works. It is visualized in the repro mission with a script that denotes the perceived position of the AI's target with circles of red smoke. Confirmed targets are discreet balls of white and red smoke.
AI listen to gunshots and make a guess of where the source (target) is. This guess has a high degree of error. They then turn towards the target or scan the horizon.
Expected: When the source of the sound is within their field of vision, they perform a Line of Sight check. If it is positive and not diluted by range or fog, they acquire the target.
Observed: Alarmed AI turn towards the source of gunfire. Before the target actually enters the unit's field of view, a Line of Sight check is performed. The AI knows exactly where the target is before actually being able to lay eyes on it. This enables them to open fire on a target instantly, with maximum accuracy. They do not actually have to spend any time looking for the target.
Expected: The AI should not perform a target-acquiring LoS check until the target is actually within their normal FoV.
Further suggestions: If the target is at long range, wearing ghillie or prone in terrain with high camouflage value (talls grass, woodland areas of the map), the LoS check should be delayed. If the target is well concealed but LoS exists, the AI should fire on an area target of several meters, gradually zeroing in on the point target.