LegendPlugin Node Documentation

This page details available nodes within LegendPlugin for modding Alien: Isolation behaviour trees. Some nodes roles are presumed and may have slight variations when actually used. Certain nodes are "built for purpose" and will crash the game if used incorrectly.

This page is currently under construction, and not all nodes are documented!

Common recurrences to note:

• Stopping distance: this is the distance as which the entity will begin to stop its movement in order to smooth the transition from active to idle (or attack). Can be used in conjunction with configured locomotion settings.
  • It is also common to have the option to play a stopping animation or not, which will further smooth the transition with a bespoke animation. This may not be required if straight switching to a kill sequence.
• Shutdown speed: a number of nodes allow for a shutdown speed request, this is believed to be how the node is cancelled by other nodes: E.G. if a move to attack is performed, it will want to be quickly shut down by a death action.
• Debug menu: the debug menu is a functionality to display behaviour options in-game and toggle them at runtime. Through modding, the debug menu can be accessed in the shipped game - but is non-functional. Nodes still exist for creating the debug menu options and checking if they are enabled at runtime, however without the functioning menu, they are redundant.
• Squad: human and android entities have squads which allows for coordination when attacking or becoming alert to an environmental state. Squads can be notified of each individual's current state, and individuals can also perform actions differently dependant on their squad being present or not (E.G. a human may want to wait to attack until it has other squad members for backup).
  • This is believed to link to the "alliance groups" which you can modify within the tool's character attribute editor.
• Objectives: each entity can have an internal objective such as get to cover, get to a safe zone, etc. This gives the entity an internal motivation while performing other actions.

Feel free to open an issue on the repo if you feel a node needs more cover in the documentation, or if any information given here is inaccurate.

Actions

Actions (under the category NodeGroupActions) are terminating nodes that perform certain logic within the behaviour tree. They end a branch and cannot lead to other nodes.

AFFECTED BY FLAMETHROWER

• Intended character: Alien
• Description: Creates a flamethrower reaction for use outside of vents.
• Options: Shutdown speed request time.

AFFECTED BY FLAMETHROWER IN VENT

• Indended character: Alien
• Description: Creates a flamethrower reaction for use in vents.
• Options: Shutdown speed request time.

ASSERT

• Intended character: N/A
• Description: Throws an assertion within the code to terminate an action. Would have been used for debugging invalid logical operations such as failing to pathfind during development.
• Options: Assertion information.

BACKSTAGE ALIEN RESPONSE

• Intended character: Human NPC
• Description: Triggers a response to hearing the alien backstage. This should be used after notifying the squad of the backstage alien discovery.
• Options: Shutdown speed request time.

BACKSTAGE AREA SWEEP

• Intended character: Alien
• Description: Forces the alien to perform a sweep of the backstage area.
• Options: Sweep with/without killtraps (vent grabs), shutdown speed request.

BREAK OUT

• Intended character: Alien
• Description: Performs a breakout action, part of the hit-and-run mechanic when an alien knocks the player down after being flamed.
• Options: Shutdown speed request time.

BROKEN COVER

• Intended character: Human NPC
• Description: Breaks the entity out of cover.
• Options: Shutdown speed request time.

CHANGE COVER

• Intended character: Human NPC
• Description: Changes the entity's current cover if another valid cover location is available (this condition should be checked first).
• Options: N/A

DEAD

• Intended character: Any
• Description: Performs the death action for the current entity.
• Options: Shutdown speed request time.

DEBUG MENU - LINK ITEM

• Intended character: N/A
• Description: Adds an item to the debug menu system, was utilised during development for toggling entity behaviours at runtime. Debug menu is no longer functional.
• Options: Text to display in the menu (also used to identify it to the conditional operator).

DESPAWN

• Intended character: Any
• Description: Despawns the current entity.
• Options: Shutdown speed request time.

DONE SYSTEMATIC SEARCH

• Intended character: Human NPC / Android
• Description: Alerts other systems that the entity has finished its systematic search operation.
• Options: N/A

EXPIRE TIMER

• Intended character: Any
• Description: Sets a specified logic timer as expired.
• Options: The timer to expire.

FAIL

• Intended character: Any
• Description: Returns a fail from the branch's current operation. The opposite of the SUCCESS node.
• Options: N/A

FORCE IDLE

• Intended character: Any
• Description: Forces the entity to go into its idle state.
• Options: Shutdown speed request time.

GET OUT OF THE WAY

• Intended character: Human NPC / Android
• Description: Tries to move the entity out of the way of action.
• Options: Shutdown speed request time.

HIT TARGET AND RUN

• Intended character:
• Description:
• Options:

IDLE

• Intended character: Any
• Description: Puts the entity into its idle state (seems to differ to FORCE IDLE in that requesting only IDLE may be overridden by other ongoing logic).
• Options: Shutdown speed request time.

IDLE IN COVER

• Intended character: Any (only humans use cover)
• Description: Puts the entity into its idle state while in cover.
• Options: Shutdown speed request time.

IDLE TIME

• Intended character: Any
• Description: Puts the entity into an idle state for a specified amount of time.
• Options: Time to be idle for, the time to account for noise, and shutdown speed request time.

IDLE TIME FACING SUSPICIOUS ITEM

• Intended character: Any
• Description: Puts the entity into an idle state for a specified amount of time while facing a suspicious item, and optionally waits for the team's arrival to leave idle.
• Options: Time to be idle for, the time to account for noise, shutdown speed request time, and if we should wait for team members to route to the suspicious item.

IDLE TIME FACING TARGET

• Intended character: Any
• Description: Puts the entity into an idle state for a specified amount of time while facing its current target.
• Options: Time to be idle for, the time to account for noise, and shutdown speed request time.

IDLE TIME FACING TARGET OUTSIDE COMBAT AREA

• Intended character: Any (only used by androids)
• Description: Puts an entity into an idle state for a specified amount of time while facing its current target that is outside the entity's combat area.
• Options: The tolerance for facing direction, the time to account for noise, the threshold qualifier type, the time to idle, and shutdown speed request time.

IDLE TIME FACING TARGET'S MOST RECENT SENSED POSITION

• Intended character: Any (only used by androids)
• Description: Puts an entity into an idle state for a specified amount of time while facing its current target's latest sensed position.
• Options: The tolerance for facing direction, the time to account for noise, the threshold qualifier type, the time to idle, and shutdown speed request time.

LISTENING IN CONVERSATION

• Intended character: Human NPC / Android
• Description: Sets the entity's current action to be the listener in a conversation.
• Options: Shutdown speed request time.

MAKE AGGRESSIVE

• Intended character: Any
• Description: Actions the entity to become aggressive.
• Options: N/A

MELEE ATTACK

• Intended character: Any
• Description: Performs a melee attack of a specified type.
• Options: The attack type to perform, and shutdown speed request time.

MOVE IN DIRECTION

• Intended character: Any
• Description: Moves the entity in a specified direction over a specified distance with a specified speed. Intended for debugging, but is still functional.
• Options: The direction, speed, and distance to move, and shutdown speed request time.

MOVE THROUGH TARGET

• Intended character: Any
• Description: Moves through a target's location at a specified speed. Will probably want to attack once we get to the target.
• Options: The speed to move at, and shutdown speed request time.

MOVE TO ATTACK TARGET

• Intended character: Any (only used for alien)
• Description: Move from the current entity's position to the target's position for an attack. Allows for a custom stopping distance to smooth the transition to kill.
• Options: The option to play a stopping animation, the distance to stop at, the speed to move at, and shutdown speed request time.

MOVE TO BACKSTAGE VIA VENT CLOSEST TO ALIEN

• Intended character: Alien
• Description: Moves the alien backstage from frontstage using the closest valid vent to itself.
• Options: Shutdown speed request time, the reason to lock the selected vent (prevents other aliens using it).

MOVE TO CONVERSATION

• Intended character: Human NPC / Android
• Description: Moves the entity to the conversation's location at a specified speed.
• Options: Speed to move to the conversation, and shutdown speed request time.

MOVE TO COVER

• Intended character: Human NPC
• Description: Moves the entity into cover if it is available (should be checked first with a conditional node).
• Options: Shutdown speed request time.

MOVE TO FRONTSTAGE VIA VENT CLOSEST TO PLAYER

• Intended character: Alien
• Description: Moves the alien back to the frontstage area from backstage, using a valid vent that is the closest to the player.
• Options: Shutdown speed request time, the reason to lock the selected vent (prevents other aliens using it).

MOVE TO MOST RECENT SENSED POSITION

• Intended character: Any
• Description: Moves the entity to the target's last sensed position at a specified speed, with the option of approaching while aimed (acting hostile).
• Options: The speed to move at, if the entity should approach aimed, and shutdown speed request time.

MOVE TO NEAREST STANDING POINT TO TARGET

• Intended character: Any
• Description: Moves the entity to the nearest standing point to the target - useful for driving tension while hiding.
• Options: The speed to move at, the stopping distance, if a stopping animation should play, and shutdown speed request time.

MOVE TO OBJECTIVE

• Intended character: Any
• Description: Moves the entity to its current objective (an objective being to get to a safe area, get to cover, etc).
• Options: The speed to move at, the type of objective to move to, and shutdown speed request time.

MOVE TO TARGET

• Intended character: Any
• Description: Moves the entity to its current target at a specified speed with a specified stopping distance.
• Options: The speed to move at, the stopping distance, if a stopping animation should play, and shutdown speed request time.

MOVE WITH GAMEPAD

• Intended character: Any
• Description: Allows programmer control of an NPC via a gamepad. Seems to be disabled in the shipping build.
• Options: Shutdown speed request time.

NOTIFY SQUAD

• Intended character: Human NPC / Android
• Description: Notifies the entity's squad of its current combat state, allows for squad coordination when an event occurs (E.G. hearing the alien backstage, becoming aggressive, etc).
• Options: The current combat state to notify the squad about.

PERFORM AMBUSH

• Intended character:
• Description:
• Options:

PERFORM ROLE

• Intended character:
• Description:
• Options:

PLAY ANIMATION TREE AND FACE TARGET

• Intended character: Any
• Description: Plays an animation tree while facing target. This is a functionality which was seemingly intended to be implemented further but reworked during development as only stun uses this functionality in the final game.
• Options: Animation callback, animation tree, and shutdown speed request time.

PLAYER CONTROLLER

• Intended character: Player
• Description: This places the player controller on the entity with this behaviour tree. Should only be given to the player, as that's who the camera is attached to.
• Options: Shutdown speed request time.

PRIMARY DAMAGE CONTROL RESPONSE

• Intended character:
• Description:
• Options:

RANGED AIM

• Intended character:
• Description:
• Options:

RANGED SHOOT

• Intended character:
• Description:
• Options:

REQUEST COVER

• Intended character:
• Description:
• Options:

SCRIPT

• Intended character: Any
• Description: Perform the entity's active script if one exists (conditional node should be used to check this first).
• Options: Shutdown speed request time.

SET FRAME FLAG

• Intended character:
• Description:
• Options:

SET GAUGE AMOUNT

• Intended character:
• Description:
• Options:

SET LOGIC CHARACTER FLAGS

• Intended character:
• Description:
• Options:

SET WITHDRAW STATE

• Intended character:
• Description:
• Options:

SPEAKING IN CONVERSATION

• Intended character:
• Description:
• Options:

START TIMER

• Intended character:
• Description:
• Options:

START TIMER (RANDOM)

• Intended character:
• Description:
• Options:

SUCCESS

• Intended character: Any
• Description: Returns a success from the current branch's execution. The opposite of the FAIL node.
• Options: N/A

SUSPECT TARGET RESPONSE

• Intended character:
• Description:
• Options:

SUSPEND

• Intended character:
• Description:
• Options:

SUSPICIOUS ITEM DONE STAGE

• Intended character:
• Description:
• Options:

SUSPICIOUS ITEM MOVE TO

• Intended character:
• Description:
• Options:

SUSPICIOUS ITEM REACTION

• Intended character:
• Description:
• Options:

SWITCH TO NEXT TARGET

• Intended character:
• Description:
• Options:

THREAT AWARE

• Intended character:
• Description:
• Options:

THREAT ESCALATION

• Intended character:
• Description:
• Options:

TRIGGER SOUND

• Intended character:
• Description:
• Options:

WEAPON EQUIP

• Intended character: Human NPC
• Description: Actions the entity to equip (or unequip) its current weapon, intended for aggressive use.
• Options: If the weapon should be equipped or unequpped, and shutdown speed request time.

---

Conditions

Conditions (under the category NodeGroupConditions) are decision nodes which switch a branch's path depending on a certain logical condition.

ALIEN CAN PERFORM ACTION

• Intended character: Alien
• Description: Returns true if the specified action can be performed, false if not.
• Options: The "alien action" to check.

ALLOWED TO ATTACK TARGET

• Intended character:
• Description:
• Options:

ALLOWED TO PURSUE TARGET

• Intended character:
• Description:
• Options:

ALLOWED TO SEARCH

• Intended character:
• Description:
• Options:

ANGLE FROM TARGET AGAINST TARGET'S CAMERA 'DIRN' LESS THAN

• Intended character:
• Description:
• Options:

ANGLE NPC TO TARGET'S AIM LESS THAN

• Intended character:
• Description:
• Options:

ANGLE TO TARGET LESS THAN

• Intended character:
• Description:
• Options:

ANOTHER ALIEN IS ATTACKING THIS TARGET

• Intended character: Alien
• Description: Returns true if another alien is already attacking the entity's target (shouldn't let multiple aliens attack one target).
• Options: N/A

CAN BE CONTROLLED BY GAMEPAD

• Intended character: Any
• Description: Checks to see if the entity can be controlled via gamepad - seems like this would've been toggled in the now disabled debug menu.
• Options: N/A

CAN BREAK OUT

• Intended character:
• Description:
• Options:

CONVERSATION INTERRUPTED

• Intended character:
• Description:
• Options:

CONVERSATION INTERRUPTED BY PLAYER

• Intended character:
• Description:
• Options:

CURRENT WEAPON IS EQUIPPED

• Intended character:
• Description:
• Options:

CURRENT WEAPON NEEDS RELOADING

• Intended character:
• Description:
• Options:

DEBUG MENU CHECK

• Intended character: N/A
• Description: Checks to see if an options is enabled/disabled in the now disabled debug menu.
• Options: The menu text of the debug menu option.

EVENT A OCCURRED AFTER EVENT B

• Intended character:
• Description:
• Options:

FINISHED MOVING AFTER SUSPICION

• Intended character:
• Description:
• Options:

FINISHED MOVING AFTER SUSPICION IN SET TIME

• Intended character:
• Description:
• Options:

HAS ALERTNESS STATE

• Intended character:
• Description:
• Options:

HAS AMBUSH POINT

• Intended character:
• Description:
• Options:

HAS ANY SENSE BEEN ABOVE THRESHOLD

• Intended character:
• Description:
• Options:

HAS ANY SENSE BEEN ABOVE THRESHOLD WITHIN A TIME

• Intended character:
• Description:
• Options:

HAS KILLTRAP

• Intended character:
• Description:
• Options:

HAS MOTIVATION

• Intended character:
• Description:
• Options:

HAS OBJECTIVE

• Intended character:
• Description:
• Options:

HAS SCRIPT

• Intended character:
• Description:
• Options:

HAS TOKEN

• Intended character:
• Description:
• Options:

HAS VALID COVER TO CHANGE TO

• Intended character:
• Description:
• Options:

HAS VALID PRIMARY TARGET

• Intended character:
• Description:
• Options:

HAS VALID ROUTE TO NEARBY TARGET

• Intended character:
• Description:
• Options:

HAS VALID ROUTE TO TARGET

• Intended character:
• Description:
• Options:

HAS VALID SECONDARY TARGET

• Intended character:
• Description:
• Options:

HAS VENT CLOSE TO ALIEN

• Intended character:
• Description:
• Options:

HAS VENT CLOSE TO PLAYER

• Intended character:
• Description:
• Options:

HAS WEAPON

• Intended character:
• Description:
• Options:

IN CONVERSATION

• Intended character:
• Description:
• Options:

IN POSITION FOR CONVERSATION

• Intended character:
• Description:
• Options:

IS ANY SENSE ACTIVATION ABOVE THRESHOLD

• Intended character:
• Description:
• Options:

IS BACKSTAGE

• Intended character:
• Description:
• Options:

IS BRANCH ACTIVE

• Intended character:
• Description:
• Options:

IS CHARACTER CLASS

• Intended character:
• Description:
• Options:

IS CORPSE TRAP

• Intended character:
• Description:
• Options:

IS COVER EXPOSED

• Intended character:
• Description:
• Options:

IS CURRENT COVER VALID

• Intended character:
• Description:
• Options:

IS DEAD

• Intended character:
• Description:
• Options:

IS ENEMY OF TARGET

• Intended character:
• Description:
• Options:

IS FRAME FLAG SET

• Intended character:
• Description:
• Options:

IS GAUGE AMOUNT ABOVE

• Intended character:
• Description:
• Options:

IS IN COMBAT AREA

• Intended character:
• Description:
• Options:

IS IN COVER

• Intended character:
• Description:
• Options:

IS IN CRAWL SPACE

• Intended character:
• Description:
• Options:

IS IN TARGETS WEAPON RANGE

• Intended character:
• Description:
• Options:

IS IN VENT

• Intended character:
• Description:
• Options:

IS PART OF NPC GROUP

• Intended character:
• Description:
• Options:

IS PERFORMING ROLE OR COULD PERFORM ROLE

• Intended character:
• Description:
• Options:

IS REQUESTING COVER

• Intended character:
• Description:
• Options:

IS SENSE ACTIVATION ABOVE

• Intended character:
• Description:
• Options:

IS TARGET IN DEEP CROUCH

• Intended character:
• Description:
• Options:

LAST TIME SEARCHED WITHIN TIME

• Intended character:
• Description:
• Options:

LAST TIME SENSED WITHIN THRESHOLD

• Intended character:
• Description:
• Options:

LAST TIME SQUAD NOTIFIED IN THRESHOLD

• Intended character:
• Description:
• Options:

LAST TIME TARGET SHOT AT US WITHIN TIME

• Intended character:
• Description:
• Options:

LAST TIME WAS ABLE TO SHOOT TARGET WAS WITHIN

• Intended character:
• Description:
• Options:

LISTENING IN CONVERSATION

• Intended character:
• Description:
• Options:

LOGIC CHARACTER FLAGS

• Intended character:
• Description:
• Options:

MELEE ATTACK AVAILABLE

• Intended character:
• Description:
• Options:

MELEE ATTACK AVAILABLE OR IS ATTACKING

• Intended character:
• Description:
• Options:

NEEDS TO GET OUT OF THE WAY

• Intended character:
• Description:
• Options:

OBJECTIVE IS IN COMBAT AREA

• Intended character:
• Description:
• Options:

OBJECTIVE IS WITHIN DISTANCE

• Intended character:
• Description:
• Options:

PLAYER IS IN EXPLOITABLE AREA

• Intended character:
• Description:
• Options:

PLAYER JOINED CONVERSATION

• Intended character:
• Description:
• Options:

RANGE TEST FOR SCRIPTED WITHDRAWAL

• Intended character:
• Description:
• Options:

REQUIRES PRIMARY DAMAGE CONTROL RESPONSE

• Intended character:
• Description:
• Options:

SCRIPTED WITHDRAWAL REQUESTED

• Intended character:
• Description:
• Options:

SEARCHED MOST RECENT SENSED POSITION

• Intended character:
• Description:
• Options:

SHOULD FOLLOW

• Intended character:
• Description:
• Options:

SHOULD PROCESS SUSPICIOUS ITEM

• Intended character:
• Description:
• Options:

SHOULD SUSPEND

• Intended character:
• Description:
• Options:

SHOULD USE COVER

• Intended character:
• Description:
• Options:

SOMEONE JOINED CONVERSATION

• Intended character:
• Description:
• Options:

SQUAD DOING ESCALATION

• Intended character:
• Description:
• Options:

SQUAD DOING SUSPICIOUS WARNING

• Intended character:
• Description:
• Options:

SUSPICIOUS ITEM - FIRST GROUP MEMBER

• Intended character:
• Description:
• Options:

SUSPICIOUS ITEM - GROUP ALLOWED TO PROGRESS

• Intended character:
• Description:
• Options:

SUSPICIOUS ITEM - GROUP MEMBERS ROUTING TO

• Intended character:
• Description:
• Options:

SUSPICIOUS ITEM - IS WITHIN DISTANCE

• Intended character:
• Description:
• Options:

SUSPICIOUS ITEM - SHOULD DO STAGE

• Intended character:
• Description:
• Options:

SUSPICIOUS ITEM - TREE PRIORITY IS

• Intended character:
• Description:
• Options:

WAIT FOR GROUP ROUTING

• Intended character:
• Description:
• Options:

TALKING IN CONVERSATION

• Intended character:
• Description:
• Options:

TARGET IS ONLY ACCESSIBLE BY CROUCHING

• Intended character:
• Description:
• Options:

TARGET IS PLAYER

• Intended character:
• Description:
• Options:

TARGET IS TARGETING ME

• Intended character:
• Description:
• Options:

TARGET IS WITHIN AGGRAVATION RADIUS

• Intended character:
• Description:
• Options:

TARGET IS WITHIN DISTANCE

• Intended character:
• Description:
• Options:

TARGET IS WITHIN DISTANCE THRESHOLD

• Intended character:
• Description:
• Options:

TARGET IS WITHIN DISTANCE UNOBSCURED

• Intended character:
• Description:
• Options:

TARGET IS WITHIN ROUTING DISTANCE

• Intended character: Any
• Description: Returns true if the entity's target is within a specified distance (calculated by pathed route), false if not.
• Options: The distance to check.

TARGET LOGIC CHARACTER FLAGS

• Intended character:
• Description:
• Options:

TARGET NEAREST STAND POINT IS WITHIN DISTANCE

• Intended character:
• Description:
• Options:

TARGET SENSED THROUGH GLASS

• Intended character:
• Description:
• Options:

TARGET'S WEAPON HAS AMMO

• Intended character:
• Description:
• Options:

TARGET'S WEAPON HAS PROPERTY

• Intended character:
• Description:
• Options:

TIMER EXPIRED

• Intended character:
• Description:
• Options:

HAS SENSE THRESHOLD LAST INCREASE ACTIVATION ABOVE

• Intended character:
• Description:
• Options:

WITHDRAW STATE

• Intended character:
• Description:
• Options:

---

Decorators

Decorator nodes (NodeGroupDecorators) transform the result of their child. A decorator node can only have one child.

AGGRESSION ESCALATION

• Intended character:
• Description:
• Options:

AWARENESS STATE

• Intended character:
• Description:
• Options:

BRANCH

• Intended character:
• Description:
• Options:

LOCK BEST VENTS

• Intended character:
• Description:
• Options:

MOOD

• Intended character:
• Description:
• Options:

PERCENTAGE

• Intended character:
• Description:
• Options:

SQUAD SEARCH

• Intended character:
• Description:
• Options:

SUSPICIOUS ITEM IN PROGRESS

• Intended character:
• Description:
• Options:

TIMER

• Intended character:
• Description:
• Options:

---

Selectors

Selector nodes (NodeGroupSelectors) are composite nodes. A selector node will return a SUCCESS if any of its children do. The children are executed in order and execution is stopped as soon as a child returns SUCCESS.

LINEAR SELECTOR

• Intended character:
• Description:
• Options:

PERCENTAGE SELECTOR

• Intended character:
• Description:
• Options:

---

Sequences

Sequence nodes (NodeGroupSequences) are also composite nodes. A sequence node is effectively an AND statement and requires all of its children to return SUCCESS.

LINEAR SEQUENCE

• Intended character:
• Description:
• Options:

STATELESS SEQUENCE

• Intended character:
• Description:
• Options: