Attack Telegraphs

Documentation Unreal Engine AI Reactions Perception

An attack announces itself at the wind-up, so a nearby enemy can parry, dodge, or stand its ground before the blow lands.

A sword touches an enemy a few hundredths of a second before it hurts them, far too late to raise a guard. The attacker announces the swing at the start of the wind-up instead, and each pawn in the danger zone decides for itself what to do about it.

When to Use This

An enemy that parries the player's attack rather than eating it.
A crowd that reacts raggedly: some dodge, some are caught out.
A parry prompt over the head of an enemy that is winding up.
A stealth opener that lands because the enemy has not spotted you yet.
A projectile, a grab, or a spell warning whatever is in front of it.

How It Works

Five stages sit between a wind-up and an enemy answering it.

The attack announces itself

SEC Attack Telegraph notify, or Report Area Stimulus from any graph

One announcement carrying the attacker, how long is left, and what kind of attack it is.

Drops out here: Nothing yet. The announcement fires once, at the instant the notify sits on.

Who is in danger

Shape, Team Filter, Notice Chance

The pawns standing inside the wedge, minus the ones the notice roll missed.

Drops out here: Anyone out of reach, behind the arc, on the attacker's own side, or unlucky on the roll.

Did this one notice

Stimulus Filters on the receiver's Enemy AI Config

The enemies that could have seen it coming.

Drops out here: Back turned, has not spotted the attacker yet, a wall in between.

What kind of answer

Trigger Rules on the receiver's Reaction Set, checked top down

A reaction category: defensive, aggressive, whatever the rule names.

Drops out here: No rule matched the tags, the rule's Chance failed, or its Min Interval has not run out.

Which reaction runs

The usual reaction scoring inside that category

One reaction, which starts its ability.

Drops out here: Nothing in the category passed its gates, so the enemy takes the hit.

Stage 2 and stage 4 each roll their own dice. Set both to 0.5 and roughly a quarter of the enemies in the arc answer.

Stages 1 to 3 decide who hears about the attack. Stages 4 and 5 hand what got through to the Reaction System, which picks and runs the answer.

The telegraph is an instant notify. It fires once, and the pawns standing on the covered ground at that instant are the ones warned. An enemy that steps into it a moment later hears nothing about that swing.

Everything on this page runs on the server. Announcements, perception, and reaction decisions all happen on the authority, which single player and a listen server give you for free.

Setup

1. Put the announcement in the attack montage

Open the attacker's montage and add the SEC Attack Telegraph notify where the wind-up starts, not where the damage does.

Details

SEC Telegraph (SECAttackTelegraphNotify)

Telegraph

Shape

Cone

Team Filter

Enemies Only

Notice Chance

0.80

Draw Debug

Origin Socket

blade_start

Time To Impact Override

Telegraph Tag

SEC.Stimulus.AttackTelegraphed

Context Tags

1 Gameplay Tag

SEC.Attack.Heavy

Magnitude

Shape

Radius

600

Half Angle Degrees

Yaw Offset Degrees

Placed on the montage where the wind-up starts. Time To Impact Override at 0 lets the notify measure the gap to the next trace window itself.

Field	Sets
Shape	The ground the warning covers. Pick Sphere to warn everything within reach, or Cone to warn a wedge pointing the way the attack is aimed. A new notify starts on Sphere, and a broadcast left with no shape warns nobody and says so in the Output Log.
Team Filter	Who gets warned. Enemies Only is what an attack wants, so allies standing in the covered ground are not startled by their own side. Team ids come from the SEC Team Interface, and an actor without one counts as neutral.
Notice Chance	How likely each pawn in range is to notice, from 0 to 1. Rolled once per pawn, so at 0.6 roughly three enemies in five spot the wind-up and the rest are caught out. Starts at 1, which warns everyone the shape covers.
Draw Debug	Draw the covered ground in the world for a moment, to check the shape against the animation.
Origin Socket	Socket the warning radiates from. Empty measures from the actor itself; name a blade socket on a long weapon so reach is measured from the tip rather than the body.
Time To Impact Override	Seconds until the blow lands, for an attack whose montage has no trace window to measure against, such as a grab or a projectile launch. Leave it at 0 and the notify works the gap out itself by finding the next melee trace window, which keeps it right when anyone retimes the animation.
Telegraph Tag	What to call this warning, which is what a trigger rule on a Reaction Set matches. Starts at `SEC.Stimulus.AttackTelegraphed`. Author a child tag for an attack that needs its own answer; a rule on the parent still catches it.
Context Tags	Extra tags describing this attack, such as `SEC.Attack.Heavy` or `SEC.Attack.Unblockable`, so a trigger rule can require or refuse them.
Magnitude	How big this attack is, in whatever units the project uses. Reaches the reaction's ability as the execution context's Magnitude.

Each shape asks for only the values it uses, so a swing that warns all round never shows an angle to fill in.

Shape	Fields
Sphere	Radius, in centimetres from where the warning starts. A pawn outside it never learns anything is coming. Starts at 500. Use it for a shockwave, a roar, or an attack wide enough that facing does not matter.
Cone	Radius as above, plus Half Angle Degrees, the width of the wedge to either side of where it is aimed (45 covers a narrow cone straight ahead, 90 covers everything in front), and Yaw Offset Degrees, which turns the wedge away from straight ahead. Set the offset to 90 for a swing coming in from the right so the warning covers where the blade goes.

AdvancedWriting a shape of your own

Subclass SEC Stimulus Shape in Blueprint for ground the built-in shapes cannot describe, such as a corridor or a ring. Answer three events:

Get Max Reach returns how far the shape can possibly reach, in centimetres. Nothing beyond it is looked at, so return the distance to the farthest corner rather than an average. A shape returning 0 warns nobody.
Covers Receiver decides whether one pawn stands on the covered ground. Everything handed to it already sits inside Get Max Reach, so a shape filling its whole reach can leave this alone.
Draw Shape outlines the ground for the debug view. Feed its World Context Object input into the same pin on every Draw Debug node used inside, not a Self node; the shape can belong to no world, so wiring Self draws nothing. Leave the event alone and the base draws a sphere at full reach, which is the outer bound rather than what Covers Receiver accepts, so a shape narrower than its reach is worth drawing properly.

One shape instance answers for every pawn a warning reaches, and a notify is shared by every montage carrying it, so keep a subclass free of stored state.

The measured Time To Impact reads the next SEC Melee Trace Window on the same montage and divides by the play rate in force, so a slowed montage reports the longer gap. A montage offering neither a trace window nor an override warns once in the Output Log and reports 0. See Melee Trace for the window itself.

2. Say what the enemy is able to notice

On the enemy's Enemy AI Config, fill in Stimulus Filters. A warning has to clear every filter before the enemy considers answering it.

Details

DA_KnightAIConfig (EnemyAIConfig)

Awareness

Stimulus Filters

3 Array elements

Facing Cone

Half Angle Degrees

100

Bypass On Context Tags

1 Gameplay Tag

SEC.Attack.Unblockable

Awareness

Minimum State

Detected

Bypass On Context Tags

0 Gameplay Tags

Line of Sight

Trace Channel

Visibility

Eye Height

Bypass On Context Tags

0 Gameplay Tags

Every filter has to pass before the enemy considers answering. An empty list notices everything, including a swing behind its back.

Filter	Checks
Facing Cone	Is the source in front of the pawn, so an enemy with its back turned is not warned about a swing it could not see coming. Half Angle Degrees starts at 100, a wide human field of view; 180 turns the filter off.
Awareness	Does the enemy already know about the source. This is the stealth case. Minimum State starts at Detected, so only an enemy watching the attacker answers its wind-up; Suspicious lets one that has heard something answer too. Needs an Awareness component on the controller; without one the filter passes and warns once.
Line of Sight	Is there a clear line, so a warning does not travel through a wall. Trace Channel starts at Visibility and Eye Height at 0, which uses the pawn's own eye height. Costs one trace per warning, and warnings are rare.

An empty list notices everything, including a swing behind the enemy's back.

Each filter carries Bypass On Context Tags: skip this filter when the warning carries any of these tags, so something loud enough to notice regardless, a roar or a shockwave, gets through a filter that would otherwise refuse it. A parent tag matches its children.

3. Say what the enemy does about it

On the enemy's Reaction Set, fill in Trigger Rules. Each rule reads as: when this kind of thing happens, try this kind of answer.

Trigger

Enabled

Rule ID

ParryFrontal

On Stimulus

SEC.Stimulus.AttackTelegraphed

Require Context Tags

0 Gameplay Tags

Block Context Tags

1 Gameplay Tag

SEC.Attack.Unblockable

Conditions

1 Array element

Index [ 0 ]

Incoming Angle Gate

Half Angle Degrees

60.0

Pass Without Direction

Invert

Answers

Reaction Links

2 Array elements

Reaction Category

SEC.Reaction.Defensive

Rule Priority

Chance

0.60

Min Interval

1.5

Field	Sets
Enabled	Turn this rule off without deleting it.
Rule ID	Short name, shown in the row title and in the logs when the rule fires or is skipped. Keep it descriptive: `ParryFrontal`, `DodgeUnblockable`.
On Stimulus	Which event this rule answers, matched against the name the warning carries. A rule on a parent tag catches every tag beneath it, so one authored on `SEC.Stimulus.AttackTelegraphed` also answers a project's own `SEC.Stimulus.AttackTelegraphed.Heavy`.
Require Context Tags	The event must carry all of these for this rule to fit, which is how a rule answers only heavy attacks. Empty requires nothing.
Block Context Tags	The rule is skipped when the event carries any of these, which is how a parry rule refuses an unblockable attack and lets the dodge rule below it answer instead. Empty refuses nothing.
Conditions	Gates that all have to pass before this rule answers. Put an Incoming Angle Gate here and the rule cannot answer a blow arriving from behind, which leaves the rule below it to take that one. Empty lets the tags decide on their own, which covers most rules.
Reaction Category	Which group of reactions answers, matching the Reaction Category on the reactions themselves.
Chance	How often this rule fires when everything else fits, from 0 to 1. 0.3 fires roughly a third of the time and lets the rules below it answer the rest, which is how an enemy parries sometimes rather than each time.
Min Interval	Shortest gap in seconds between two firings of this rule, so an enemy cannot parry every swing of a fast combo. Counted from the moment the rule started a reaction, not from each time it was considered. 0 sets no limit.

The enemy checks the rules from the top down and takes the first one that fits and yields a reaction, so put the specific ones above the general ones.

A rule names a category, not a reaction. The usual reaction scoring picks the winner inside that category, which means one rule covers parry, dodge, and backstep together. Trigger rules live on the Reaction Set rather than the component, so an enemy that swaps to an Elite set picks up that set's triggers with it. A set with no rules authored answers nothing on its own, which leaves an enemy on reactions fired by hand from Blueprint.

4. Make a reaction answer only what it can stop

On the parry reaction spec, under Scoring, add the Incoming Angle Gate and set its Half Angle Degrees.

Field	Sets
Half Angle Degrees	Half the width of the arc the blow must arrive inside, in degrees to either side of straight ahead. 60 accepts anything up to 60 degrees off the front; 180 accepts every direction, which turns the gate off. Starts at 60.
Pass Without Direction	Let something through when there is no direction to measure. On by default, so a reaction fired by hand still works. Untick it to refuse anything the gate cannot judge.

A blow from the side fails the parry's gate and the dodge wins instead, with no second rule.

The same gate goes in a rule's Conditions instead when the whole category is the wrong answer. The two placements read differently:

Placed in	Decides	A refusal means
A rule's Conditions	Whether this kind of answer is considered at all	The next rule down takes the stimulus
A reaction's Scoring	Whether this reaction is the right one inside a category that already matched	Another reaction in the same category takes it

Reach for the rule when nothing in the category can help. A hit landing from behind reports itself like any other, and a guard raised against it stops nothing, because the Defense component measures its own arc when the damage lands and refuses the block. Gate the rule instead and write a second rule under it:

Order	Rule	Conditions	Answers with
1	GuardFrontal	Incoming Angle Gate, half angle 60	Your defensive category
2	FlinchAnything	none	Your stagger category

A frontal blow takes rule 1 and gets the guard. A blow from behind fails rule 1's condition, falls to rule 2, and gets a flinch. Match the gate's Half Angle Degrees to the arc on the matching Defense response so the decision and the damage agree.

Four gates read the stimulus rather than the pawn, so each one belongs in a rule's Conditions or a reaction's Scoring:

Gate	Judges
Incoming Angle	Which side the blow arrives from.
Time To Impact	Whether there is time left to answer. Min Seconds set to the parry's own start-up stops it answering a swing already too close, and stops a parry rule answering a hit that already landed, which reports no time left.
Stimulus Magnitude	How big it is, in whatever the producer measured: incoming damage for a hit, a 0 to 1 charge for a wind-up. A ceiling on one rule and a floor on the next splits a flinch from a stagger.
Source Distance	How far off the attacker stands, measured to the source actor or to the stimulus origin when nothing named a source.

An action never carries a stimulus, so one of these added to an action has nothing to judge and passes.

Two dice, at two different stages

Notice Chance on the announcement and Chance on a trigger rule are separate rolls, and they multiply. Notice Chance rolls once per pawn when the warning goes out and decides who hears about it. Chance rolls when the enemy reaches a matching rule and decides how often one that heard answers. Set both to 0.5 and roughly a quarter of the enemies in the arc react.

Notice Chance is the crowd knob: it makes a group look like individuals rather than one mind. Chance is the per-enemy knob, and it makes a single enemy read as fallible. Reach for Notice Chance when four enemies all parry the same swing, and for Chance when one enemy parries too often.

A parry prompt for the player

The player wants the warning without any of the AI machinery behind it.

Add SEC Stimulus Listener to the player pawn.
Bind On Stimulus Noticed.
Read the payload. Source is who is attacking, Time To Impact is how long is left, and Context Tags says whether the attack is unblockable, so the prompt can show red rather than white.
Show the widget above Source's head, and hide it when Time To Impact runs out.

The player gets no perception filters by design. The player's eyes are the camera. The delegate fires for every announcement that reaches the pawn with nothing filtered out first, so branch on the stimulus when a prompt should stay hidden for an attack the player is facing away from.

Key the widget by Source and refresh it rather than spawning a new one. A moving attacker re-announces, and each announcement carries a fresher Time To Impact. Treat repeats as updates.

The listener decides nothing on its own: no filters, no trigger rules, no reactions. An AI pawn needs none of it, since its controller's Reaction Evaluation component already receives the same announcements.

Announcing without a montage

Report Area Stimulus is the same call the notify makes, available from any event graph. Reach for it for a projectile, a grab, a spell going off, or a scripted moment.

A fireball warns what is in front of it on spawn: pass the projectile as Source, its velocity as Facing, a radius and a narrow arc as the Shape, and a stimulus carrying SEC.Stimulus.AttackTelegraphed with the seconds until it arrives.

BP_Fireball · Event BeginPlay

TargetSelf

Return Value

SourceSelf

Stimulus

Shape

Facing

Return Value

The node returns how many pawns were told, which is worth printing while tuning a radius. Facing falls back to the source actor's forward vector when left at zero, and the stimulus Origin falls back to the source actor's location.

A projectile with no team id reads as neutral, and an Enemies Only filter then lets it warn your own side along with the target. Copy the shooter's team id onto it when you spawn it.

Debugging

SEC.Debug.Stimulus.Draw 1

Draws the announced radius, arc, and facing at its origin, then one sphere at every pawn the announcement reached, coloured by what happened, with a line back to the origin and a label naming the outcome. Markers last two seconds, and the same lines go to the Output Log.

Orangethe announcement

Drawn at the origin: a sphere for the reach, the covered wedge, and an arrow for the facing, labelled with the tag, the radius, the arc and the notice chance.

GreyTeam filtered

The team filter refused this pawn, which is what keeps an attack from startling its own side.

BlueOutside shape

In range but off the ground the shape covers. Widen the shape, or turn a cone with its yaw offset.

MagentaNotice roll failed

The announcement's Notice Chance dropped this pawn before its own perception ran.

RedNot noticed

One of the receiver's Stimulus Filters refused it. The label names which filter.

YellowNo reaction

Noticed, and nothing answered. The label says why: no trigger rule matched, or nothing in the category passed its gates.

GreenReacted

A reaction started, and the label names it.

CyanListener only

A pawn carrying a Stimulus Listener and no reaction component, which is the player.

WhiteNo receiver

Neither a reaction component nor a listener, so the announcement reached a pawn that cannot use it.

Draw Debug on one broadcast turns the same drawing on for that announcement alone. The console variable forces it on for all of them.

Read the colours as a funnel. Grey, blue, and magenta mean the announcement itself is mis-shaped: widen the radius or the arc, check the team ids, raise the notice chance. Red means the receiver's own perception refused it, and the label names the filter. Yellow means the enemy noticed and had no answer, which points at the trigger rules or at the gates on the reactions in that category.

AdvancedAnswering a hit that already landed

Report Damage Taken Stimulus covers the other half of the story: a flinch or a counter after a blow connects. Call it from the pawn's Handle Incoming Damage once the damage is resolved, and it reads the direction the blow came from off the damage info.

Leave Stimulus Tag empty for SEC.Stimulus.DamageTaken. A trigger rule on that tag answers it the way another rule answers a telegraph, so a flinch reaction and a parry reaction sit side by side in one Reaction Set.

Make Stimulus From Damage packages the same thing without reporting it, for a graph that wants to change a field before handing it on.

AdvancedThe order of checks inside a trigger rule

For each rule, top down: the stimulus tag has to match, then Require Context Tags, then Block Context Tags, then Min Interval, then every gate in Conditions, then Chance, and finally the category has to yield a reaction that passes its own gates. The enemy drops a rule that gets all the way through and finds nothing available, and the next rule down takes its turn.

One scoring context is built for the whole Conditions list, so several gates on one rule measure the same moment. An empty row in the list is skipped rather than treated as a refusal.

Chance rolls last among the rule's own checks, so a rule that cannot fire does not burn the roll. The component stamps Min Interval when the rule started a reaction, and skips the stamp when the reaction refused to start.

On Stimulus Received on the Reaction Evaluation component fires before the rule walk. Call Execute Reaction from there and the rules sit out that announcement, since a rule only fires when nothing already answered.

AdvancedReplacing a whole stage

Two Blueprint-overridable events on the Reaction Evaluation component let a project take a stage over outright.

Override	Replaces
Can Sense Stimulus	The whole perception step. The default runs every filter in force and requires all of them to pass.
Select Reaction Category	The whole rule walk. Return a category tag to route an announcement a project's own way without authoring rules.

Fallback Stimulus Filters on the component covers a pawn running without an AI Config. A config that lists any filters replaces that list outright rather than adding to it.

Writing a filter or a condition of your own is a Blueprint subclass either way: SEC Stimulus Filter answers Can Sense, and SEC Gate answers Passes Gate with the scoring context of the pawn, the target, and whatever set it off. A rule's Conditions take the same gate class an action or a reaction takes, so one gate you write serves all three. Keep both stateless, since every AI using the asset shares one instance.

C++The stimulus struct

FSECCombatStimulus is the package the whole pipeline passes around.

Field	Carries
`StimulusTag`	What happened, which is what a trigger rule matches on.
`Source`	Who produced it, usually the attacker. The reaction that answers receives it as its target. Weak, so a source destroyed before the reaction runs reads as none.
`Origin`	Where in the world it came from, for a spell landing across the room from whoever cast it.
`Direction`	Pointing from the source toward the receiver, normalized. The Incoming Angle Gate reads it straight off.
`Magnitude`	How big it is, in the producer's own units. Reaches the ability as the execution context's Magnitude.
`TimeToImpact`	Seconds until the blow is expected to land. 0 for something that already happened.
`ContextTags`	Extra tags describing it, read by trigger rules, filter bypasses, and the ability.
`Payload`	Any object the producer wants to hand along, such as the weapon or the projectile. Weak.

UReactionEvaluationComponent* Reactions = USECStimulusLibrary::FindReactionComponent(Receiver);
Reactions->ReceiveStimulus(Stimulus);

FindReactionComponent answers with the component on the pawn's controller, or one on the actor itself. MakeExecutionContextFromStimulus fills an FSECExecutionContext from a stimulus, so a reaction started by hand reaches its ability carrying what an automatic one would.

MultiplayerMultiplayer

Report Area Stimulus reports nothing when the source is not the authority, and the notify returns early on any machine that is not the server. A montage playing on a client announces nothing, so one swing cannot warn the same enemy twice.

Receive Stimulus and Report Stimulus To are server side for the same reason. The On Stimulus Noticed delegate on a listener therefore fires on the server; a true multiplayer parry prompt needs that replicated down to the owning client.

Clients see the outcome through the reaction ability and its animation, which replicate the way every other ability does. See Multiplayer.

Page	Why
Reaction System	Stages 4 and 5: the reaction set, the gates and scorers, and what happens once a reaction starts.
Defense System	What the raised guard is worth once the blow arrives.
Awareness System	The perception memory the Awareness filter reads, and the stealth opener it makes possible.
Melee Trace	The trace window the notify measures its time to impact against.
Animation Integration	The rest of the montage surface, including the windows that hold a defensive state tag.