Actions
In the GOAP system, an action represents a discrete step an agent can undertake to achieve a specific goal. Actions are defined by their requirements and effects, which guide the chaining of actions to form a plan.
Components of an Action
Actions are composed of four primary parts:
Config: Configuration settings for the action.
Action Class: The logic and behavior of the action.
Action Data: Temporary data storage for the action's state.
Action Props: Additional properties for the action.
Action Config
The configuration provides essential settings for the action, enabling its integration into the GOAP graph.
Conditions
Conditions are a set of world states that must be met for the action to be executable. Each condition references a WorldKey
and specifies whether its value should be true or false.
Effects
Effects describe the changes in world states that result from performing the action. Each effect references a WorldKey
and indicates the expected outcome (true or false).
BaseCost
This represents the inherent cost of executing the action, excluding any additional costs (like distance) that the planner might add.
Target
Every action has an associated target position. Before executing the action, the agent will move towards this target, depending on the MoveMode
. Targets are identified using TargetKey
, such as ClosestApple
or ClosestEnemy
.
StopppingDistance
This value specifies the proximity required between the agent and the target position before the action can commence.
MoveMode
MoveMode
determines how the action and movement are coordinated:
MoveBeforePerforming: The agent moves to the target position before initiating the action.
PerformWhileMoving: The agent concurrently moves to the target and executes the action.
Action Data
Action data provides temporary storage for the action's state for an individual agent. This data is not shared across agents or across multiple invocations of the same action.
Action Props
Action props are additional properties that can be used to customize the action's behavior. They are defined as fields in the action class and can be set as configuration values on ScriptableObjects or through code.
Action Data Injection
To reference other classes on the agent, use the GetComponent
attribute. This provides a cached component instance, optimizing performance by avoiding frequent GetComponent
calls.
Action Class
The action class defines the behavior of the action. It should be stateless since a single instance might be used to execute the same action on different agents. The class inherits from ActionBase<TData>
, where TData
is the action data class.
IActionRunState Interface
The IActionRunState
interface is a crucial component in the GOAP system. It defines the contract for action run states, which are responsible for determining the behavior of actions during their execution. These states decide when an action should be updated, stopped, performed, completed, or even resolved. They can also be used to 'pause' running an action, and come back later to continue it.
Methods
void Update(IAgent agent, IActionContext context)
: Updates the state of the action based on the current context and agent state. This method is called every frame during the action's execution.bool ShouldStop(IAgent agent)
: Determines whether the action should be stopped. If this method returnstrue
, the action will be stopped.bool ShouldPerform(IAgent agent)
: Determines whether the action should continue performing. If this method returnstrue
, the action will continue its execution.bool IsCompleted(IAgent agent)
: Checks if the action has been completed. If this method returnstrue
, the action is considered completed.bool MayResolve(IAgent agent)
: Determines whether the action may resolve based on the current state of the agent. This is used for actions that have conditional completion criteria.bool IsRunning()
: Indicates whether the action is currently running. This can be used to check the state of the action outside of the usual update cycle.
Usage
IActionRunState
allows for the creation of custom run states for actions, providing flexibility in how actions are executed within the GOAP system. By implementing this interface, developers can define custom logic for when actions should start, stop, or update, allowing for complex behavior patterns.
Several predefined action run states are provided out of the box, such as Continue
, Stop
, Completed
, and various Wait
states, to cover common use cases.
Example
Here's a simple example of a custom action run state that stops the action after a certain time has elapsed:
Examples
The provided examples illustrate how to implement specific functionalities within the action class and action data. They've been retained in their original form for clarity.
Examples
Last updated