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EQS Node Reference: Contexts

Describes how Contexts are used within Tests and Generators in the EQS system.

Unreal Engine 4.21

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EnvQueryContext_Item
EnvQueryContext_Querier
EnvQueryContext_BlueprintBase

Within the Environment Query System (EQS), Contexts provide a frame of reference for any

[Tests](Engine/ArtificialIntelligence/EQS/EQSNodeReference/EQSNodeReferenceTests)

[Generators](Engine/ArtificialIntelligence/EQS/EQSNodeReference/EQSNodeReferenceGenerators)

used. A Context can be as simple as the Querier (who is performing the Test) or more complex such as All Actors of a Type. A Generator, such as a Points: Grid, can use a Context that returns multiple locations or Actors. This will create a grid (of the defined size and density) at the location of each Context. In addition to Engine supplied Contexts, you can create custom Contexts in Blueprint with the EnvQueryContext_BlueprintBase class or through C++ code.

EnvQueryContext_Item

Items are created by the Generator, and if using the EQS Testing Pawn, they are the spheres that appear in the Editor. An EnvQueryContext_Item is either a location (FVector) or an Actor (AActor).

EnvQueryContext_Querier

The Querier is the Pawn that is currently possessed by an AI Controller and is executing the

[Behavior Tree](Engine/ArtificialIntelligence/BehaviorTrees)

that initiated the Environment Query. An example of where Querier as the Context could be used is if you want to search the environment around the AI character for an item they can use, or to find a place that provides cover from the player, or just to determine the current location of the AI performing the query.

In the Details panel for a Generator type, you can assign the Querier as a Context for the following properties:


Generator	Property
Actors of Class	Search Center
Current Location	Query Context
Points: Circle	Circle Center
Points: Cone	Center Actor
Points: Donut	Center
Points: Grid	Generate Around
Points: Pathing Grid	Generate Around

EnvQueryContext_BlueprintBase

You can create a custom Context through Blueprint using the EnvQueryContext_BlueprintBase Class. This provides four functions that can be overridden, enabling you to add your own custom Contexts for use within Tests in a query.

To use a custom Context:

Create a new Blueprint of the EnvQueryContext_BlueprintBase class.
In EnvQueryContext_BlueprintBase, click Override and select the type of function you wish to use.

Refer to the table below a description of each function override:


Function	Description
Provide Single Location	This returns a single location (vector). How you generate that location is up to you. For example, the function below will return the trace hit location of a random Actor (one that is found in the DesiredObjectType array, such as Pawn, Vehicle) found within 1500 cm of the Querier: Click for full image.
Provide Single Actor	This returns a single Actor. You can obtain that Actor through any method you desire. In this example, the function will return Player 0's controlled Actor:
Provide Locations Set	This returns an array of locations (vectors). How you generate these locations is up to you. In the example below, this function will trace from 16 evenly spaced locations on a circle with a radius of 1500 units, returning successful hits on the environment: Click for full image.
Provide Actors Set	This returns an array of Actors. You can use any desired method to obtain those Actors. In the example below, we use a Get All Actors of Class node to retrieve our specified class as the Actors to return: