Memory

Search & evidence#

Things you leave behind that an AI can find, a search that sends it where you could plausibly be, and places it will never look.

APS Evidence, APS Observer and APS Search componentsThe APS Knowledge module (part of APS)Demo: rooms Q5 and M4

The 30-second version

Room Q5. A forced lock is APS Evidence: the guard who finds it believes someone was here, and searches the points around it (the circles), the most likely first.

Add APS Evidence to anything an AI should be able to find: a body, a forced lock, blood.
An AI with APS Observer discovers it and fires On Evidence Discovered.
APS Search hands out the best place to look next, and Is Search Exhausted says when it has looked everywhere.

Evidence#

APS Evidence turns any actor into something an AI can discover and draw a conclusion from. Add the component: that is the setup.

Setting	Default	What it does
`Evidence Tag`	Evidence	What kind of thing it is: Body, ForcedLock, Blood, Footprints
`Conspicuousness`	0.6	How obvious it is, 0 to 1: 1 a body in a corridor, 0.2 a scuff mark. An AI has to be closer to notice the subtle ones.
`Belief Strength`	0.8	How strongly finding it convinces the AI: the confidence of the belief it forms
`Lifetime Seconds`	0	Fades away on its own after this long; 0 stays until removed
`Instigator`	(none)	Who did it, if your game knows: carried into the finder's memory
`Implied Direction`	(0, 0, 0)	Which way they went: drag marks, a blood trail, a door left swinging
`Auto Register as Perceivable`	On	Register itself so AI can perceive it, with nothing else to do

Get Age says how long it has existed ("still warm"); Remove Evidence takes it away: a body dragged off, a stain mopped up.

Implied Direction is the useful one. Most evidence says something happened here; evidence with a direction says and they went that way, which turns a sweep into a pursuit.

Discovering it#

An AI with an APS Observer component and Discover Evidence on finds evidence near it and fires On Evidence Discovered (Evidence Actor, Evidence Tag, Location), once per piece. By then the AI already holds a belief about that place. The rest is your logic: raise the alarm, start a search, change the patrol, file a memory. Get Discovered Evidence Count says how many it has found.

Evidence is a thing, not someone

A body is a thing found, not a person seen, and APS keeps them apart on purpose: an AI that took a body for someone would chase a target lying at its feet. An actor with APS Evidence is perceived as a thing: Get Belief Data and Get Perceived Objects say how well the AI has seen it, but it is never a target. No On AI Suspect, On AI Detect, On AI See or On AI Telegraph names it, it takes no attention, raises no threat, and Get Targets Sorted by Score leaves it out. Finding it is the Observer's On Evidence Discovered.

Any actor can be a thing without being evidence: call Set Perceived as Object on the APS subsystem. A guard that dies is the usual case: mark its body (or give it APS Evidence, which does the same) and the guards around it stop treating it as a person on their next update.

Search#

APS Search answers one question again and again: they were last seen here, and I've already looked there: where next?

On AI Lost (Target, Last Known)
  → Begin Search (Last Known)

Behavior Tree:
  → Get Best Search Point → Point
  → Move To (Point's Location)
  → Branch: Is Search Exhausted → give up, back to patrol

Node	What it does
Begin Search (Last Known Location)	Start searching around a point (replaces any search running)
End Search	Stop
Is Searching	Is one running?
Get Best Search Point	The single best place to look next; false when nothing is left
Get Ranked Search Points (Count)	The best few, most promising first: one each for a squad
Mark Cleared (Location, Radius)	"I've looked here": for a look through a window, or a squadmate's search
Is Search Exhausted	It has looked everywhere it can reach
Get Search Progress	How much of the reachable area is checked, 0 to 1
Get Search Duration	Seconds since Begin Search

It clears as it walks: while searching, everywhere the AI goes counts as checked (every quarter second, within Clear Radius). Call Mark Cleared yourself only for places it checked without walking there.

Setting	Default	What it does
`Cell Size`	300	Grid resolution in cm: smaller is more precise and costs more
`Grid Radius`	20	Half-width of the grid in cells: 20 at 300 cm covers a 120 m square
`Target Speed`	450	How fast the target could move, in cm/s: what turns elapsed time into an area. Set it near your player's sprint.
`Clear Radius`	450	How close the AI must get before a place counts as checked
`Require Navigable`	On	Only hand out places on the navmesh that the AI can walk to

Go deeperHow it ranks, and the navmesh

Probability follows reachability, not distance: the most likely place isn't next to where it lost you, because you've had time to move. The peak sits at the edge of how far you could plausibly have got, and it widens as time passes.

Points respect the navmesh, so the AI never searches inside a wall:

each point is the cell's spot on the navmesh, never a cell centre inside a wall or over a gap;
the first time a point comes up, APS checks the AI has a full path to it; a place it can't walk to (a closed room, a roof, the far side of a wall) is skipped for the rest of the search;
reaching a point clears its cell, even when the point sits off the cell's centre.

So every point is one an AI MoveTo can walk to, and Is Search Exhausted doesn't wait on places nobody can reach. One query path-tests at most 32 points; past that, points are handed out untested and checked on a later call, so a query never stalls a frame. With no navigation in the level (or Require Navigable off), every cell is accepted: a plain widening area.

Places it never searches#

Room M4. A designer-marked safe room (the green zone): the guard chases you to it, then searches everywhere but inside.

Give the player a guaranteed safe space: Register Never Search Zone (Center, Radius) on the APS subsystem marks a sphere; Unregister Never Search Zone and Clear Never Search Zones remove them.

APS doesn't enforce it by itself: your search and chase logic asks Is Location in Never Search Zone (on APS Core, which respects the profile's Respect Never Search Zones) before sending the AI somewhere, as the demo's M4 guard does.

The demo's safe zone Blueprint — BP_SafeZone › Set Zone On: unregister the zone, then register it again (Register Never Search Zone) when it is switched on.

Putting it together#

All of it your logic, with the parts APS gives you:

The player breaks a lock and leaves. The lock has APS Evidence: tag ForcedLock, Implied Direction down the corridor.
A guard with an APS Observer walks past: On Evidence Discovered fires.
Your Blueprint calls Begin Search at the lock, and Remember on a place subject so the guard finds that corridor suspicious for the rest of the session (Memory).
The Behavior Tree runs Get Best Search Point → move, until Is Search Exhausted.
The guard gives up; the memory of that corridor stays.