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 move to a given destination. At regular intervals, the path to the destination will be recalculated. If you want to make the AI to follow a particular object you can attach the AIDestinationSetter component. Take a look at the Get Started With The A* Pathfinding Project tutorial for more instructions on how to configure this script.

Here is a video of this script being used move an agent around (technically it uses the Pathfinding.Examples.MineBotAI script that inherits from this one but adds a bit of animation support for the example scenes):

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 destination field 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 maxSpeed is self-explanatory, as is rotationSpeed. however slowdownDistance might require some explanation: It is the approximate distance from the target where the AI will start to slow down. Setting it to a large value will make the AI slow down very gradually. pickNextWaypointDist determines the distance to the point the AI will move to (see image below).

Below is an image illustrating several variables that are exposed by this class (pickNextWaypointDist, steeringTarget, desiredVelocity)

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 finds a character controller it will also use that. If it finds a rigidbody it will use that. Lastly it will fall back to simply modifying Transform.position which is guaranteed to always work and is also the most performant option.

How it works

In this section I'm going to go over how this script is structured and how information flows. This is useful if you want to make changes to this script or if you just want to understand how it works a bit more deeply. However you do not need to read this section if you are just going to use the script as-is.

This script inherits from the AIBase class. The movement happens either in Unity's standard Update or FixedUpdate method. They are both defined in the AIBase class. Which one is actually used depends on if a rigidbody is used for movement or not. Rigidbody movement has to be done inside the FixedUpdate method while otherwise it is better to do it in Update.

From there a call is made to the MovementUpdate method (which in turn calls MovementUpdateInternal). This method contains the main bulk of the code and calculates how the AI *wants* to move. However it doesn't do any movement itself. Instead it returns the position and rotation it wants the AI to move to have at the end of the frame. The Update (or FixedUpdate) method then passes these values to the FinalizeMovement method which is responsible for actually moving the character. That method also handles things like making sure the AI doesn't fall through the ground using raycasting.

The AI recalculates its path regularly. This happens in the Update method which checks shouldRecalculatePath and if that returns true it will call SearchPath. The SearchPath method will prepare a path request and send it to the Seeker component which should be attached to the same GameObject as this script. Since this script will when waking up register to the Seeker.pathCallback delegate this script will be notified every time a new path is calculated by the OnPathComplete method being called. It may take one or sometimes multiple frames for the path to be calculated, but finally the OnPathComplete method will be called and the current path that the AI is following will be replaced.

Public Member Functions
Vector3	CalculateVelocity (Vector3 position)
	Current desired velocity of the agent (excluding physics and local avoidance but it includes gravity). More...
virtual void	OnTargetReached ()
	The end of the path has been reached. More...
override void	Teleport (Vector3 newPosition, bool clearPath=true)
	Instantly move the agent to a new position. More...
Public Member Functions inherited from AIBase
virtual void	FinalizeMovement (Vector3 nextPosition, Quaternion nextRotation)
	Moves the agent to a position. More...
virtual Vector3	GetFeetPosition ()
	Position of the base of the character. More...
virtual void	Move (Vector3 deltaPosition)
	Move the agent. More...
void	MovementUpdate (float deltaTime, out Vector3 nextPosition, out Quaternion nextRotation)
	Calculate how the character wants to move during this frame. More...
virtual void	SearchPath ()
	Recalculate the current path. More...
void	SetPath (Path path)
	Make the AI follow the specified path. More...
Quaternion	SimulateRotationTowards (Vector3 direction, float maxDegrees)
	Simulates rotating the agent towards the specified direction and returns the new rotation. More...
Public Member Functions inherited from IAstarAI
void	FinalizeMovement (Vector3 nextPosition, Quaternion nextRotation)
	Move the agent. More...
void	Move (Vector3 deltaPosition)
	Move the agent. More...
void	MovementUpdate (float deltaTime, out Vector3 nextPosition, out Quaternion nextRotation)
	Calculate how the character wants to move during this frame. More...
void	SearchPath ()
	Recalculate the current path. More...
void	SetPath (Path path)
	Make the AI follow the specified path. More...

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. More...
bool	constrainInsideGraph = false
	Ensure that the character is always on the traversable surface of the navmesh. More...
float	endReachedDistance = 0.2F
	Distance to the end point to consider the end of path to be reached. More...
float	maxAcceleration = -2.5f
	How quickly the agent accelerates. More...
float	pickNextWaypointDist = 2
	How far the AI looks ahead along the path to determine the point it moves to. More...
float	rotationSpeed = 360
	Rotation speed in degrees per second. More...
float	slowdownDistance = 0.6F
	Distance from the end of the path where the AI will start to slow down. More...
bool	slowWhenNotFacingTarget = true
	Slow down when not facing the target direction. More...
CloseToDestinationMode	whenCloseToDestination = CloseToDestinationMode.Stop
	What to do when within endReachedDistance units from the destination. More...
Public Attributes inherited from AIBase
bool	canMove = true
	Enables or disables movement completely. More...
bool	canSearch = true
	Enables or disables recalculating the path at regular intervals. More...
float	centerOffset = 1
	Offset along the Y coordinate for the ground raycast start position. More...
Vector3	gravity = new Vector3(float.NaN, float.NaN, float.NaN)
	Gravity to use. More...
LayerMask	groundMask = -1
	Layer mask to use for ground placement. More...
float	maxSpeed = 1
	Max speed in world units per second. More...
IMovementPlane	movementPlane = GraphTransform.identityTransform
	Plane which this agent is moving in. More...
float	repathRate = 0.5f
	Determines how often the agent will search for new paths (in seconds). More...
bool	rotationIn2D = false
	If true, the forward axis of the character will be along the Y axis instead of the Z axis. More...
bool	updatePosition = true
	Determines if the character's position should be coupled to the Transform's position. More...
bool	updateRotation = true
	Determines if the character's rotation should be coupled to the Transform's rotation. More...

Protected Member Functions
virtual void	CalculateNextRotation (float slowdown, out Quaternion nextRotation)
override Vector3	ClampToNavmesh (Vector3 position, out bool positionChanged)
	Constrains the character's position to lie on the navmesh. More...
override void	MovementUpdateInternal (float deltaTime, out Vector3 nextPosition, out Quaternion nextRotation)
	Called during either Update or FixedUpdate depending on if rigidbodies are used for movement or not. More...
override void	OnDisable ()
override void	OnPathComplete (Path newPath)
	Called when a requested path has been calculated. More...
override int	OnUpgradeSerializedData (int version, bool unityThread)
	Handle serialization backwards compatibility. More...
Protected Member Functions inherited from AIBase
	AIBase ()
void	ApplyGravity (float deltaTime)
	Accelerates the agent downwards. More...
Vector2	CalculateDeltaToMoveThisFrame (Vector2 position, float distanceToEndOfPath, float deltaTime)
	Calculates how far to move during a single frame. More...
virtual void	CalculatePathRequestEndpoints (out Vector3 start, out Vector3 end)
	Outputs the start point and end point of the next automatic path request. More...
void	CancelCurrentPathRequest ()
virtual void	FindComponents ()
virtual void	FixedUpdate ()
	Called every physics update. More...
virtual void	OnDrawGizmos ()
virtual void	OnDrawGizmosSelected ()
virtual void	OnEnable ()
	Called when the component is enabled. More...
Vector3	RaycastPosition (Vector3 position, float lastElevation)
	Checks if the character is grounded and prevents ground penetration. More...
Quaternion	SimulateRotationTowards (Vector2 direction, float maxDegrees)
	Simulates rotating the agent towards the specified direction and returns the new rotation. More...
virtual void	Start ()
	Starts searching for paths. More...
virtual void	Update ()
	Called every frame. More...
void	UpdateVelocity ()
Protected Member Functions inherited from VersionedMonoBehaviour
virtual void	Awake ()

Protected Attributes
PathInterpolator	interpolator = new PathInterpolator()
	Helper which calculates points along the current path. More...
Path	path
	Current path which is followed. More...
Protected Attributes inherited from AIBase
CharacterController	controller
	Cached CharacterController component. More...
Vector2	lastDeltaPosition
	Amount which the character wants or tried to move with during the last frame. More...
float	lastDeltaTime
	Delta time used for movement during the last frame. More...
float	lastRepath = float.NegativeInfinity
	Time when the last path request was started. More...
int	prevFrame
	Last frame index when prevPosition1 was updated. More...
Vector3	prevPosition1
	Position of the character at the end of the last frame. More...
Vector3	prevPosition2
	Position of the character at the end of the frame before the last frame. More...
Rigidbody	rigid
	Cached Rigidbody component. More...
Rigidbody2D	rigid2D
	Cached Rigidbody component. More...
RVOController	rvoController
	Cached RVOController component. More...
Seeker	seeker
	Cached Seeker component. More...
Vector3	simulatedPosition
	Position of the agent. More...
Quaternion	simulatedRotation
	Rotation of the agent. More...
Transform	tr
	Cached Transform component. More...
Vector2	velocity2D
	Current desired velocity of the agent (does not include local avoidance and physics). More...
float	verticalVelocity
	Velocity due to gravity. More...
bool	waitingForPathCalculation = false
	Only when the previous path has been calculated should the script consider searching for a new path. More...

Properties
bool IAstarAI.	canMove [get, set]
	Enables or disables movement completely. More...
bool IAstarAI.	canSearch [get, set]
	Enables or disables recalculating the path at regular intervals. More...
bool	hasPath [get]
	True if this agent currently has a path that it follows. More...
float IAstarAI.	maxSpeed [get, set]
	Max speed in world units per second. More...
bool	pathPending [get]
	True if a path is currently being calculated. More...
bool	reachedEndOfPath [get, protected set]
	True if the agent has reached the end of the current path. More...
float	remainingDistance [get]
	Remaining distance along the current path to the end of the path. More...
float	speed [get, set]
	Maximum speed in world units per second. More...
Vector3	steeringTarget [get]
	Point on the path which the agent is currently moving towards. More...
Vector3	targetDirection [get]
	Direction that the agent wants to move in (excluding physics and local avoidance). More...
bool	TargetReached [get]
	True if the end of the path has been reached. More...
float	turningSpeed [get, set]
	Rotation speed. More...
Properties inherited from AIBase
Vector3	desiredVelocity [get]
	Velocity that this agent wants to move with. More...
Vector3	destination [get, set]
	Position in the world that this agent should move to. More...
bool	isStopped [get, set]
	Gets or sets if the agent should stop moving. More...
System.Action	onSearchPath [get, set]
	Called when the agent recalculates its path. More...
Vector3	position [get]
	Position of the agent. More...
Quaternion	rotation [get]
	Rotation of the agent. More...
virtual bool	shouldRecalculatePath [get]
	True if the path should be automatically recalculated as soon as possible. More...
Transform	target [get, set]
	Target to move towards. More...
bool	usingGravity [get, private set]
	Indicates if gravity is used during this frame. More...
Vector3	velocity [get]
	Actual velocity that the agent is moving with. More...
Properties inherited from IAstarAI
bool	canMove [get, set]
	Enables or disables movement completely. More...
bool	canSearch [get, set]
	Enables or disables recalculating the path at regular intervals. More...
Vector3	desiredVelocity [get]
	Velocity that this agent wants to move with. More...
Vector3	destination [get, set]
	Position in the world that this agent should move to. More...
bool	hasPath [get]
	True if this agent currently has a path that it follows. More...
bool	isStopped [get, set]
	Gets or sets if the agent should stop moving. More...
float	maxSpeed [get, set]
	Max speed in world units per second. More...
System.Action	onSearchPath [get, set]
	Called when the agent recalculates its path. More...
bool	pathPending [get]
	True if a path is currently being calculated. More...
Vector3	position [get]
	Position of the agent. More...
bool	reachedEndOfPath [get]
	True if the agent has reached the end of the current path. More...
float	remainingDistance [get]
	Remaining distance along the current path to the end of the path. More...
Quaternion	rotation [get]
	Rotation of the agent. More...
Vector3	steeringTarget [get]
	Point on the path which the agent is currently moving towards. More...
Vector3	velocity [get]
	Actual velocity that the agent is moving with. More...

Static Private Attributes
static NNConstraint	cachedNNConstraint = NNConstraint.Default

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

CalculateNextRotation()

virtual void CalculateNextRotation ( float  slowdown, out Quaternion  nextRotation  )

protectedvirtual

CalculateVelocity()

Vector3 CalculateVelocity

(

Vector3

position

)

Current desired velocity of the agent (excluding physics and local avoidance but it includes gravity).

Deprecated:

This method no longer calculates the velocity. Use the desiredVelocity property instead.

ClampToNavmesh()

override Vector3 ClampToNavmesh ( Vector3  position, out bool  positionChanged  )

protectedvirtual

Constrains the character's position to lie on the navmesh.

Not all movement scripts have support for this.

Parameters

position	Current position of the character.
positionChanged	True if the character's position was modified by this method.

Returns

New position of the character that has been clamped to the navmesh.

Reimplemented from AIBase.

MovementUpdateInternal()

override void MovementUpdateInternal ( float  deltaTime, out Vector3  nextPosition, out Quaternion  nextRotation  )

protectedvirtual

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

Implements AIBase.

OnDisable()

override void OnDisable ( )

protectedvirtual

Reimplemented from AIBase.

OnPathComplete()

override void OnPathComplete ( Path  newPath )

protectedvirtual

Called when a requested path has been calculated.

A path is first requested by #UpdatePath, 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.

Implements AIBase.

Reimplemented in LegacyAIPath.

OnTargetReached()

virtual void OnTargetReached ( )

virtual

The end of the path has been reached.

If you want custom logic for when the AI has reached it's destination add it here. You can also create a new script which inherits from this one and override the function in that script.

This method will be called again if a new path is calculated as the destination may have changed. So when the agent is close to the destination this method will typically be called every repathRate seconds.

OnUpgradeSerializedData()

override int OnUpgradeSerializedData ( int  version, bool  unityThread  )

protectedvirtual

Handle serialization backwards compatibility.

Reimplemented from AIBase.

Teleport()

override void Teleport ( Vector3  newPosition, bool  clearPath = true  )

virtual

Instantly move the agent to a new position.

This will trigger a path recalculation (if clearPath is true, which is the default) so if you want to teleport the agent and change its destination it is recommended that you set the destination before calling this method.

The current path will be cleared by default.

See also

Works similarly to Unity's NavmeshAgent.Warp.

SearchPath

Reimplemented from AIBase.

Member Data Documentation

alwaysDrawGizmos

bool alwaysDrawGizmos

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

cachedNNConstraint

NNConstraint cachedNNConstraint = NNConstraint.Default

staticprivate

constrainInsideGraph

bool constrainInsideGraph = false

Ensure that the character is always on the traversable surface of the navmesh.

When this option is enabled a GetNearest query will be done every frame to find the closest node that the agent can walk on and if the agent is not inside that node, then the agent will be moved to it.

This is especially useful together with local avoidance in order to avoid agents pushing each other into walls.

See also

Local Avoidance for more info about this.

This option also integrates with local avoidance so that if the agent is say forced into a wall by other agents the local avoidance system will be informed about that wall and can take that into account.

Enabling this has some performance impact depending on the graph type (pretty fast for grid graphs, slightly slower for navmesh/recast graphs). If you are using a navmesh/recast graph you may want to switch to the RichAI movement script which is specifically written for navmesh/recast graphs and does this kind of clamping out of the box. In many cases it can also follow the path more smoothly around sharp bends in the path.

It is not recommended that you use this option together with the funnel modifier on grid graphs because the funnel modifier will make the path go very close to the border of the graph and this script has a tendency to try to cut corners a bit. This may cause it to try to go slightly outside the traversable surface near corners and that will look bad if this option is enabled.

Warning

This option makes no sense to use on point graphs because point graphs do not have a surface. Enabling this option when using a point graph will lead to the agent being snapped to the closest node every frame which is likely not what you want.

Below you can see an image where several agents using local avoidance were ordered to go to the same point in a corner. When not constraining the agents to the graph they are easily pushed inside obstacles.

endReachedDistance

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 reachedEndOfPath will return true.

interpolator

PathInterpolator interpolator = new PathInterpolator()

protected

Helper which calculates points along the current path.

maxAcceleration

float maxAcceleration = -2.5f

How quickly the agent accelerates.

Positive values represent an acceleration in world units per second squared. Negative values are interpreted as an inverse time of how long it should take for the agent to reach its max speed. For example if it should take roughly 0.4 seconds for the agent to reach its max speed then this field should be set to -1/0.4 = -2.5. For a negative value the final acceleration will be: -acceleration*maxSpeed. This behaviour exists mostly for compatibility reasons.

In the Unity inspector there are two modes: Default and Custom. In the Default mode this field is set to -2.5 which means that it takes about 0.4 seconds for the agent to reach its top speed. In the Custom mode you can set the acceleration to any positive value.

path

Path path

protected

Current path which is followed.

pickNextWaypointDist

float pickNextWaypointDist = 2

How far the AI looks ahead along the path to determine the point it moves to.

In world units. If you enable the alwaysDrawGizmos toggle this value will be visualized in the scene view as a blue circle around the agent.

Here are a few example videos showing some typical outcomes with good values as well as how it looks when this value is too low and too high.

{aipath/picknext/video_02_default.mp4}	A too low value and a too low acceleration will result in the agent overshooting a lot and not managing to follow the path well.
{aipath/picknext/video_02_100.mp4}	A low value but a high acceleration works decently to make the AI follow the path more closely. Note that the AILerp component is better suited if you want the agent to follow the path without any deviations.
{aipath/picknext/video_07_default.mp4}	A reasonable value in this example.
{aipath/picknext/video_10_default.mp4}	A reasonable value in this example, but the path is followed slightly more loosely than in the previous video.
{aipath/picknext/video_20_default.mp4}	A too high value will make the agent follow the path too loosely and may cause it to try to move through obstacles.

rotationSpeed

float rotationSpeed = 360

Rotation speed in degrees per second.

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.

slowdownDistance

float slowdownDistance = 0.6F

Distance from the end of the path where the AI will start to slow down.

slowWhenNotFacingTarget

bool slowWhenNotFacingTarget = true

Slow down when not facing the target direction.

Incurs at a small performance overhead.

whenCloseToDestination

CloseToDestinationMode whenCloseToDestination = CloseToDestinationMode.Stop

What to do when within endReachedDistance units from the destination.

The character can either stop immediately when it comes within that distance, which is useful for e.g archers or other ranged units that want to fire on a target. Or the character can continue to try to reach the exact destination point and come to a full stop there. This is useful if you want the character to reach the exact point that you specified.

Note

reachedEndOfPath will become true when the character is within endReachedDistance units from the destination regardless of what this field is set to.

Property Documentation

canMove

bool IAstarAI. canMove

getsetprivate

Enables or disables movement completely.

If you want the agent to stand still, but still react to local avoidance and use gravity: use isStopped instead.

This is also useful if you want to have full control over when the movement calculations run. Take a look at MovementUpdate

See also

canSearch

isStopped

canSearch

bool IAstarAI. canSearch

getsetprivate

Enables or disables recalculating the path at regular intervals.

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

Note that this only disables automatic path recalculations. If you call the SearchPath() method a path will still be calculated.

See also

canMove

isStopped

hasPath

bool hasPath

get

True if this agent currently has a path that it follows.

maxSpeed

float IAstarAI. maxSpeed

getsetprivate

Max speed in world units per second.

pathPending

bool pathPending

get

True if a path is currently being calculated.

reachedEndOfPath

bool reachedEndOfPath

getprotected set

True if the agent has reached the end of the current path.

This is the approximate distance the AI has to move to reach the end of the path it is currently traversing.

Note that setting the destination does not immediately update the path, nor is there any guarantee that the AI will actually be able to reach the destination that you set. The AI will try to get as close as possible.

It is very hard to provide a method for detecting if the AI has reached the destination that works across all different games because the destination may not even lie on the navmesh and how that is handled differs from game to game (see also the code snippet in the docs for destination).

See also

remainingDistance

remainingDistance

float remainingDistance

get

Remaining distance along the current path to the end of the path.

For the RichAI movement script this may not always be precisely known, especially when far away from the destination. In those cases an approximate distance will be returned.

If the agent does not currently have a path, then positive infinity will be returned.

See also

reachedEndOfPath

speed

float speed

getset

Maximum speed in world units per second.

Deprecated:

Use maxSpeed instead

steeringTarget

Vector3 steeringTarget

get

Point on the path which the agent is currently moving towards.

This is usually a point a small distance ahead of the agent or the end of the path.

If the agent does not have a path at the moment, then the agent's current position will be returned.

targetDirection

Vector3 targetDirection

get

Direction that the agent wants to move in (excluding physics and local avoidance).

Deprecated:

Only exists for compatibility reasons. Use desiredVelocity or steeringTarget instead instead.

TargetReached

bool TargetReached

get

True if the end of the path has been reached.

Deprecated:

When unifying the interfaces for different movement scripts, this property has been renamed to reachedEndOfPath

turningSpeed

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 files:

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