AIPath Class Reference

AI for following paths. More...

Detailed Description

AI for following paths.

This AI is the default movement script which comes with the A* Pathfinding Project. It is in no way required by the rest of the system, so feel free to write your own. But I hope this script will make it easier to set up movement for the characters in your game. This script works well for many types of units, but if you need the highest performance (for example if you are moving hundreds of characters) you may want to customize this script or write a custom movement script to be able to optimize it specifically for your game.

This script will try to follow a target transform. At regular intervals, the path to that target will be recalculated. It will in the Update method try to move towards the next point in the path. However it will only move in roughly forward direction (Z+ axis) of the character, but it will rotate around it's Y-axis to make it possible to reach the target.

Quick overview of the variables

In the inspector in Unity, you will see a bunch of variables. You can view detailed information further down, but here's a quick overview.
The repathRate determines how often it will search for new paths, if you have fast moving targets, you might want to set it to a lower value.
The target variable is where the AI will try to move, it can be a point on the ground where the player has clicked in an RTS for example. Or it can be the player object in a zombie game.
The speed is self-explanatory, so is rotationSpeed, however slowdownDistance might require some explanation. It is the approximate distance from the target where the AI will start to slow down.
pickNextWaypointDist is simply determines within what range it will switch to target the next waypoint in the path.

Below is an image illustrating several variables as well as some internal ones, but which are relevant for understanding how it works.

Note

The image is slightly outdated, replace forwardLook with pickNextWaypointDist in the image and ignore the circle for pickNextWaypointDist.

This script has many movement fallbacks. If it finds an RVOController attached to the same GameObject as this component, it will use that. If it fins a character controller it will also use that. Lastly if will fall back to simply modifying Transform.position which is guaranteed to always work and is also the most performant option.

Public Member Functions
virtual Vector3	GetFeetPosition ()
void	OnDisable ()
virtual void	OnPathComplete (Path _p)
	Called when a requested path has finished calculation.
virtual void	OnTargetReached ()
virtual void	SearchPath ()
	Requests a path to the target.
float	TrySearchPath ()
	Tries to search for a path.

Public Attributes
bool	alwaysDrawGizmos
	Draws detailed gizmos constantly in the scene view instead of only when the agent is selected and settings are being modified.
bool	canMove = true
	Enables or disables movement.
bool	canSearch = true
	Enables or disables searching for paths.
float	endReachedDistance = 0.2F
	Distance to the end point to consider the end of path to be reached.
float	pickNextWaypointDist = 2
	Determines within what range it will switch to target the next waypoint in the path.
float	repathRate = 0.5F
	Determines how often it will search for new paths.
float	rotationSpeed = 360
	Rotation speed.
float	slowdownDistance = 0.6F
	Distance from the target point where the AI will start to slow down.
float	speed = 3
	Maximum velocity.
Transform	target
	Target to move towards.
Public Attributes inherited from AIBase
float	centerOffset = 1
	Offset along the Y coordinate for the ground raycast start position.
Vector3	gravity = new Vector3(float.NaN, float.NaN, float.NaN)
	Gravity to use.
LayerMask	groundMask = -1
	Layer mask to use for ground placement.

Protected Member Functions
override void	MovementUpdate (float deltaTime)
	Called during either Update or FixedUpdate depending on if rigidbodies are used for movement or not.
virtual void	OnEnable ()
	Run at start and when reenabled.
override int	OnUpgradeSerializedData (int version)
	Handle serialization backwards compatibility.
IEnumerator	RepeatTrySearchPath ()
	Tries to search for a path every repathRate seconds.
virtual void	Start ()
	Starts searching for paths.
Protected Member Functions inherited from AIBase
void	ApplyGravity (float deltaTime)
override void	Awake ()
	Initializes reference variables.
Vector2	CalculateDeltaToMoveThisFrame (Vector2 position, float distanceToEndOfPath, float deltaTime)
virtual Vector3	ClampToNavmesh (Vector3 position)
	Constrains the character's position to lie on the navmesh.
virtual void	FixedUpdate ()
	Called every physics update.
void	Move (Vector3 position3D, Vector3 deltaPosition)
virtual void	OnDrawGizmos ()
Vector3	RaycastPosition (Vector3 position, float lastElevation)
	Find the world position of the ground below the character.
virtual void	RotateTowards (Vector2 direction, float maxDegrees)
	Rotates in the specified direction.
virtual void	Update ()
	Called every frame.

Protected Attributes
bool	canSearchAgain = true
	Only when the previous path has been returned should be search for a new path.
PathInterpolator	interpolator = new PathInterpolator()
float	lastRepath = -9999
	Time when the last path request was sent.
Path	path
	Current path which is followed.
Vector3	targetPoint
	Point to where the AI is heading.
Vector3	velocity
Protected Attributes inherited from AIBase
CharacterController	controller
	Cached CharacterController component.
IMovementPlane	movementPlane = GraphTransform.identityTransform
Rigidbody	rigid
	Cached Rigidbody component.
Rigidbody2D	rigid2D
	Cached Rigidbody component.
RVOController	rvoController
	Cached RVOController component.
Seeker	seeker
	Cached Seeker component.
Transform	tr
	Cached Transform component.
Vector2	velocity2D
	Current desired velocity of the agent.
float	verticalVelocity
	Velocity due to gravity.

Properties
bool	TargetReached [get, set]
	True if the end of the path has been reached.
float	turningSpeed [get, set]
	Rotation speed.
Properties inherited from AIBase
bool	usingGravity [get, set]
	Indicates if gravity is used during this frame.

Private Attributes
bool	startHasRun = false
	True if the Start function has been executed.

Additional Inherited Members
Static Protected Attributes inherited from AIBase
static readonly Color	GizmoColorRaycast = new Color(118.0f/255, 206.0f/255, 112.0f/255)

Member Function Documentation

virtual Vector3 GetFeetPosition ( )

virtual

override void MovementUpdate ( float  deltaTime )

protectedvirtual

Called during either Update or FixedUpdate depending on if rigidbodies are used for movement or not.

Implements AIBase.

void OnDisable

(

)

virtual void OnEnable ( )

protectedvirtual

Run at start and when reenabled.

Starts RepeatTrySearchPath.

See Also

Start

virtual void OnPathComplete ( Path  _p )

virtual

Called when a requested path has finished calculation.

A path is first requested by SearchPath, it is then calculated, probably in the same or the next frame. Finally it is returned to the seeker which forwards it to this function.

Reimplemented in LegacyAIPath.

virtual void OnTargetReached ( )

virtual

Reimplemented in MineBotAI.

override int OnUpgradeSerializedData ( int  version )

protectedvirtual

Handle serialization backwards compatibility.

Reimplemented from VersionedMonoBehaviour.

IEnumerator RepeatTrySearchPath ( )

protected

Tries to search for a path every repathRate seconds.

See Also

TrySearchPath

virtual void SearchPath ( )

virtual

Requests a path to the target.

virtual void Start ( )

protectedvirtual

Starts searching for paths.

If you override this function you should in most cases call base.Start () at the start of it.

See Also

OnEnable

RepeatTrySearchPath

Reimplemented in MineBotAI.

float TrySearchPath

(

)

Tries to search for a path.

Will search for a new path if there was a sufficient time since the last repath and both canSearchAgain and canSearch are true and there is a target.

Returns

The time to wait until calling this function again (based on repathRate)

Member Data Documentation

bool alwaysDrawGizmos

Draws detailed gizmos constantly in the scene view instead of only when the agent is selected and settings are being modified.

bool canMove = true

Enables or disables movement.

See Also

canSearch

bool canSearch = true

Enables or disables searching for paths.

Setting this to false does not stop any active path requests from being calculated or stop it from continuing to follow the current path.

See Also

canMove

bool canSearchAgain = true

protected

Only when the previous path has been returned should be search for a new path.

float endReachedDistance = 0.2F

Distance to the end point to consider the end of path to be reached.

When the end is within this distance then OnTargetReached will be called and TargetReached will return true.

PathInterpolator interpolator = new PathInterpolator()

protected

float lastRepath = -9999

protected

Time when the last path request was sent.

Path path

protected

Current path which is followed.

float pickNextWaypointDist = 2

Determines within what range it will switch to target the next waypoint in the path.

float repathRate = 0.5F

Determines how often it will search for new paths.

If you have fast moving targets or AIs, you might want to set it to a lower value. The value is in seconds between path requests.

float rotationSpeed = 360

Rotation speed.

Rotation is calculated using Quaternion.RotateTowards. This variable represents the rotation speed in degrees per second. The higher it is, the faster the character will be able to rotate.

float slowdownDistance = 0.6F

Distance from the target point where the AI will start to slow down.

Note that this doesn't only affect the end point of the path but also any intermediate points, so be sure to set pickNextWaypointDist to a higher value than this

float speed = 3

Maximum velocity.

This is the maximum speed in world units per second.

bool startHasRun = false

private

True if the Start function has been executed.

Used to test if coroutines should be started in OnEnable to prevent calculating paths in the awake stage (or rather before start on frame 0).

Transform target

Target to move towards.

The AI will try to follow/move towards this target. It can be a point on the ground where the player has clicked in an RTS for example, or it can be the player object in a zombie game.

Vector3 targetPoint

protected

Point to where the AI is heading.

Vector3 velocity

protected

Property Documentation

bool TargetReached

getset

True if the end of the path has been reached.

float turningSpeed

getset

Rotation speed.

Deprecated:

This field has been renamed to rotationSpeed and is now in degrees per second instead of a damping factor.

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The documentation for this class was generated from the following file:

• /Users/arong/Unity/a-pathfinding-project/Assets/AstarPathfindingProject/Core/AI/AIPath.cs