Enemy Behavior describes various actions or tactics enemies employ while spawned in the game. While based mostly on when enemies are alerted to the player's presence, this can include behavioral traits observed while the enemy is unaware of the player as well.
When enemies attempt to engage the player, they will attempt to avoid obstacles (including other enemies) in order to reach them. When hidden by various means such as by the use of Shade, 's , or 's , enemies will only know the players' location by the sound of their weapons. If they are silenced or by using , the enemies may attempt to find cover or run toward the player but still will not know exactly where they are.
Abilities such as 's suffer from the inability of enemies to continue to fall into his pool, since enemies that have sunken into the pool at the edge are objects that other enemies can detect, thus will stand directly at the edge of the pool, unable to go in until the enemies at the edge are dead. This kind of pathing issues can be exploited in some ways, however, such as standing on some kinds of boxes or objects in small rooms with doors on either side, as enemies will stop at a certain point and wait until the player comes down, often grouping up in massive numbers in some cases, allowing AoE weapons to make quick work of them. This can also decrease the number of enemies spawned in Survival missions, as enemies who were targeting this unreachable player will stop wherever they are on the map unless another player is in view.
It can be noted that enemies may become bugged, not moving on upper or lower levels of the mission just aiming their weapon around, or pacing around. It is unknown what causes this issue but it will cause enemy spawn rates in the immediate area to drop significantly in Survival missions, halting progress a bit.
WARFRAME utilizes a navigation mesh (NavMesh) on Tile Sets to aid NPC pathfinding through a level. In gameplay environments where 3D movement is more prevalent (such as Archwing missions), the game uses a Sparse Voxel Octree (SVO) to map traversable terrain in a level. Pathfinding algorithms include greedy A*. For obstacle avoidance in 3D movement, the game uses an optimal reciprocal collision avoidance (ORCA) algorithm.
When an enemy is unalerted, they will walk around, chatter, or stay stationary while looking around casually. On the mini-map, unalerted enemies will have a red, hollow arrow when detected on your radar. While their paths can be noted and remembered, enemies do not execute the same pathing routine every time and may switch it up on occasion. It can be noted that while enemies are unalerted, problems with pathing become apparent, such as groups of Grineer attempting to go into opposing rooms but neither side will move out of the way to allow this, causing them to get stuck in doorways you may need to cross without alerting them, which becomes almost impossible. Enemies may also spawn in large groups, making stealth kills more tricky to execute without alerting the others.
In the case of Grineer enemies with helmets, their helmets will sometimes oddly move independently of the facial mesh underneath when unalerted, with the mask "looking" in a certain direction while the Grineer walks forward and keeps their head centered. This does not affect where they are looking, and they will still have their vision pointed forward.
A Stealth Kill occurs when you kill an enemy who is not aware of any of its enemies, including wild creatures. Killing an enemy will produce Sound that is loud enough to travel about 5 meters, and enemies within that range will become cautious and become alerted for around 20 seconds. Killing those enemies while alerted will break the stealth kill bonus, but after this point, they can be stealth killed and they will count towards stealth kills. If invisible, you can tell when this is available on human targets if you are given the opportunity to stealth kill them while close to them.
Note that this makes it extremely hard to do stealth kills on tight groups with melee weapons, and impossible to execute with frames that are not under , or , as enemies will immediately turn around to see you attacking the enemy.
Newly spawned enemies or enemies that the game teleports in front of the player have a timer before stealth kills are counted. This timer, which can be around 4-8 seconds or in rare cases indefinitely, killing this otherwise unalerted enemy will not count as a stealth kill, and thus will reset any stealth bonus multiplier you have if this enemy is killed. There is no way of knowing if an enemy just spawned in or teleported from another cell. This is why players may notice that despite all enemies being unaware of your presence, killing them all at once with an explosive weapon will often not give you any stealth affinity, or will break your current stealth multiplier.
There are two kinds of alerted state that enemies can be in.
- Cautious: The enemy has become alerted, but has not spotted the player (or anything that is considered to be an enemy toward them). They will aim their gun (or if they are melee, will have a more aggressive stance) and walk around, searching the area.
- Spotting a player for a very brief moment but losing visual contact, seeing a dead body, or hearing a sound without spotting the player will activate this alerted state.
- If they do not become alerted further, after about 20-30 seconds they will cancel their alerted state.
- When cautious, they will have a red arrow with an arrow in the centre when detected on your mini-map radar.
- Alerted: The alarms are active on the level and/or the enemy has visually spotted their target (the player or otherwise)
- In this state, the enemy has increased awareness and will spot the player from much further away, as well as enemies who see you will let the enemies nearby know where you are as well.
- When alerted, the enemy will have a solid, red arrow when detected on your mini-map radar.
Things to note:
- Nullifiers of both kinds will have their bubbles disabled if they are not alerted, allowing stealth kills. Becoming alerted will raise their bubble, and damaging this bubble will alert the Nullifier. Nullifiers that become unalerted, when previously in a cautious or alerted state will have their bubble become disabled again.
- If enemies see an arrow or bolt landing on a surface in their line of sight (such as an arrow or bullet shot by their feet) they will go into the cautious state unless they see you as well.
- Firing at an enemy that does not die instantly will alert them. If they see you, or you are not cloaked when they are alerted, all enemies in that area will also become alerted. The Nox seems to be a notable exception to this rule as receiving damage in regions outside of his field of view does not seem to alert him (Confirmation needed).
- A Fire Hazard currently active on the mission will cause all enemies to be in a cautious state.
- Note that this makes stealth kills impossible as enemies will always spawn alerted and slightly more aggressive into finding you.
- If their ally is killed within their field of view, they will become cautious, disallowing stealth kills, but will not alert others or trigger the alarms unless the player is seen as well.
Enemy Awareness: In Hotfix 19.6.3 (2017-01-17), enemy AI was changed for most enemies, that requires visual contact with the player for them to become fully alerted. Otherwise, enemies will remain in their cautious state and move to where they heard a gunshot and then search the immediate area. Before, if you were invisible with any ability or companion and then decloaked, enemies would know exactly where you were and would run to your location. Now, they must require direct visual contact or hear a sound you make with a weapon in order to know where you are. One enemy seeing the player is enough to make the others cautious, but they will not pursue the player unless the alarms have been activated as well.
Enemies who are alerted will have specific walk styles or behaviors, which helps the player know if the enemy is currently suspicious. Cautioned enemies (enemies who were alerted for some reason but do not know of the players' position) will walk with their guns aimed and walk with larger distances between steps. Corpus robots will lower their bodies slightly while their guns move back and forth, looking for players, and Corpus Ospreys will have their wings out and move around faster. Some enemies are more difficult to tell if they are unalerted, like Grineer Butchers, whose walk is more upright and aggressive when alerted but otherwise identical to their unalerted stance (at least when walking, when they stop moving they hold their weapon and swing it around). Some enemies are impossible to know if they are alerted or not, such as Grineer Rollers or Drahks, who have the same moving style regardless of their alert status, unless you look at their arrow status when detected on your mini-map radar.
To become unalerted from an alerted state, several conditions must be met:
- The alarms in the area have been reset by hacking a console that appears white on the map.
- 30 seconds to over a minute have passed since alerting the enemies.
- Enemies who were crouching behind cover will still continue their animation as if still alerted, but if the conditions above are met, they will be considered unalerted and can be killed stealthily.
- As stated above, if there is a Fire Hazard on the tileset, they will rarely become unalerted even when hacking a console to remove alarms.
- Most humanoid enemies besides melee-focused enemies like Butchers or Prod Crewmen, and enemies who are disarmed, will attempt to find cover in most mission types. Exceptions include Defense, Excavation, and Survival type missions, where enemies aggressively move toward players or defense objectives and rarely take cover.
- They will, however, prioritize their Blunts when available.
- Enemies behind cover may wait for an opportunity to throw a Grenade, indicated by the enemy peeking up or around their cover a few times before lobbing the grenade.
- Enemies are more likely to lob grenades at the player if they are attempting to take cover or simply are not moving. Players who continue to move around discourage enemies to throw grenades as they attempt to track the player instead. This does not completely prevent them from throwing grenades, however.
- Grineer enemies often use military-like tactics against the player, especially while in groups. Lone Grineer may backtrack a way to where a group of Grineer is, then move along with the group at a steady pace towards the player, attempting to overwhelm them with firepower while melee units rush in faster.
- This appears to be a less common tactic in the latest versions of the game.
- If Shield Lancers are in the area, Grineer are more likely to backtrack once they notice the player, even if they cannot take advantage of the shield due to other units already behind it.
- When a unit runs out of ammo in their current magazine, they will be more likely to strafe sideways or move backwards, or even choose to get behind cover (even if they already reloaded). This is not true with heavy units, which still do not choose to hide in any case.
- The only enemy units in the Infested faction that do not rush the player are Swarm-Mutalist MOAs and Tar-Mutalist MOAs, which keep at a medium distance from the player while using their devastating ranged attacks, as they have no natural melee abilities. This makes the Infested faction largely melee-focused which makes tactics that exploit AI pathing is ineffective at best.
- Various Grineer units will carry inflatable barriers called Blunts, shown by a small pack on their back. Occasionally, they will throw it down and enemies will treat the object like cover, or players can also use it as mildly effective cover as well. The Blunt has a limited amount of HP, in which it will pop and deflate, remaining crumpled on the ground for the rest of the mission.
- Tall enemies have limited use of the cover, one reason on account of them never taking cover in the first place, and secondly, it makes them easy to pick off with headshots, as their heads will be over the barrier.
- It can be mildly effective for the player against enemy bullets, but has no effect against the attacks of Bombards and Napalms.
- Deflated Blunts serve as places where new ones will be placed, causing Grineer to sometimes walk over to place one, while not attacking the player.
- As a result, destroying Blunts will offer a small relief from enemies as they move out of the battle to place them.
Enemies Behind Cover
Enemies that are currently taking advantage of some sort of cover act differently than normal units. Some units obtain the ability to burst fire their weapons, even Ballistas or Corrupted Crewmen. Enemies are also far more likely to throw grenades at the player while behind cover, besides when shielded by Shield Lancers.
- Spawning describes when an enemy is rendered and placed into the game environment. In Warframe, enemies always spawn in set spots in any given cell. Due to how Warframe renders game environments and how it connects different cells together, these spawn points can be learned by players and exploited, noted below.
- The game will spawn enemies at a certain distance away from players, often in rooms that are dead ends but can spawn in visual range as well, including directly next to the player if they attempt to stay in one spot for too long to discourage camping behavior. If players are all in one area, all enemies will spawn around them and move in, maximizing resource collection and shared experience. If players spread out across the entire map enemies will spawn in chunks and often attack one player (usually the host) more, with more than half of the enemies spawning to attack that player more often.
- Some instances have been noted (even recently) with spawn points spawning enemies right in front of the player despite the player moving through the level normally.
- If the area is currently not alerted by alarms or there is no Fire Hazard, enemies will be spawned unalerted (with the aforementioned spawning penalty listed above).
- In Sortie missions, enemies are always spawned alerted to the player's presence to prevent XP exploits.
- Enemies do not de-spawn in WARFRAME. Instead, the game will temporarily remove the enemies that are too far away from the player and replace them closer to the player. This is easily observed with enemies who are under the effects of as they will spawn near the player again, and still be under the abilities affect.
- When being moved, these enemies may repeat their "stunned" animation from the ability as well.
Enemies in Exterminate missions, and especially the Grineer, will run to extraction if you leave them behind. After walking at least 70 meters away (depends on unknown factors) they will begin to run to extraction and ignore dead bodies on the way there. They are not considered to be alerted when in this state, but they will count as alerted if they see dead bodies. Once at extraction, they will cluster together and walk around aimlessly.
This was implemented to give players the illusion that the entire map is filled with enemies, and so enemies will always be at extraction if players rush through the level. Newly spawned enemies in other rooms when the player is near extraction will also run to extraction, allowing the player to essentially stay in one spot and let enemies come to them.
Interestingly, the game will almost always spawn two Eximus units near extraction on Grineer Exterminates but it is unknown why this occurs.
Enemies Under Various Crowd Control
A general list of various things enemy units will do when under the effect of various crowd control effects, abilities, or status effects.
- While blinded by , , or , enemies will move toward the sounds made by players most of the time, but may stay put in one spot and simply aim their guns in the direction they last heard the player.
- Enemies who move around will usually do so slowly.
- Guardsmen will rush the player and melee in their general direction.
- While under the effects of Radiation procs, enemies will be vulnerable to friendly fire. They will also begin to attack other enemies when the player moves out of range.
- If the alarms have not been activated, this may cause enemies to activate them.
- Enemies under will follow the player unless enemies fire upon them, and will then fire on those enemies when they get into range.
- All enemies seem to spawn unalerted except in certain conditions. This can be exploited in some occasions by noting enemy spawn points and shooting them the moment they spawn, granting stealth kill bonuses and thus bonus affinity, even when there are other alerted enemies in the area. As per Hotfix 18.0.4 (2015-12-08) this has changed. Enemies slain within ~8 seconds of spawning will no longer count towards stealth kills (unconfirmed for client, confirmed for host).
- For clients, this is easier to execute due to even the slightest latency increasing the window in which an enemy spawns unalerted, and is changed to alerted. In survival missions, standing at least 40 meters or so from the spawn point, have your ally either stand next to or behind you, and enemies from that spawn point will occasionally spawn, allowing you to gain bonus affinity. It is not known if allies will benefit from this bonus affinity, but due to how bonus affinity is gained it is assumed they do.
- Capture missions are one of the few mission types which have a forced "Alerted" enemy state after the Lotus says you found the target. Until the Lotus exclaims you found the target (even if you are far away) all present enemies and newly spawned enemies will be in an unalerted state.
- Sometimes an enemy's idle animation will override their alerted state, which causes some enemies to look unalerted while standing in one spot, despite their seeing you kill an enemy and actually being alerted.
- This seems to be the most common with non-melee focused enemies.
- Brewer, Daniel (2015). Getting off the NavMesh: Navigating in Fully 3D Environments. GDCVault. Accessed 2022-04-11. Archived from the original on 2022-04-11. For presentation slides see https://gdcvault.com/play/1022017/Getting-off-the-NavMesh-Navigating.