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 destination.

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Note: The image is slightly outdated, replace forwardLook with pickNextWaypointDist in the image and ignore the circle for pickNextWaypointDist.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
Vector3	CalculateVelocity (Vector3 position)
	Current desired velocity of the agent (excluding physics and local avoidance but it includes gravity).

override void	OnPathComplete (Path newPath)
	Called when a requested path has been calculated.

virtual void	OnTargetReached ()
	The end of the path has been reached.

override void	Teleport (Vector3 newPosition, bool clearPath=true)
	Instantly move the agent to a new position.

Public Member Functions inherited from AIBase
virtual Vector3	GetFeetPosition ()
	Position of the base of the character.

void	MovementUpdate (float deltaTime, bool useGravity)
	Calculate all movement for a single movement step and move the character.

virtual void	SearchPath ()
	Recalculate the current path.

Public Member Functions inherited from IAstarAIMovement
Vector3	ClampToNavmesh (Vector3 position, out bool positionChanged)
	Clamps the agent's position to the navmesh.

void	Move (Vector3 position, Vector3 deltaPosition)
	Move the agent.

void	RotateTowards (Vector3 direction, float maxDegrees)
	Rotates towards the specified direction.

void	UpdateVelocity (Vector3 position)
	To be called after all movement is done with the position of the agent.

Public Member Functions inherited from IAstarAI
void	MovementUpdate (float deltaTime, bool useGravity)
	Calculate all movement for a single movement step and move the agent.

void	SearchPath ()
	Recalculate the current path.

void	Teleport (Vector3 newPosition, bool clearPath=true)
	Instantly move the agent to a new position.

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.

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	rotationSpeed = 360
	Rotation speed.

float	slowdownDistance = 0.6F
	Distance from the target point where the AI will start to slow down.

bool	slowWhenNotFacingTarget = true
	Slow down when not facing the target direction.

CloseToDestinationMode	whenCloseToDestination = CloseToDestinationMode.Stop
	What to do when within endReachedDistance units from the destination.

Public Attributes inherited from AIBase
bool	canMove = true
	Enables or disables movement completely.

bool	canSearch = true
	Enables or disables recalculating the path at regular intervals.

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.

float	maxSpeed = 1
	Max speed in world units per second.

IMovementPlane	movementPlane = GraphTransform.identityTransform
	Plane which this agent is moving in.

float	repathRate = 0.5f
	Determines how often the agent will search for new paths (in seconds).

bool	rotationIn2D = false
	If true, the forward axis of the character will be along the Y axis instead of the Z axis.

bool	updatePosition = true
	Determines if the character should move or if just the desired velocities should be calculated.

bool	updateRotation = true
	Determines if the character should rotate automatically.

Protected Member Functions
override void	MovementUpdateInternal (float deltaTime)
	Called during either Update or FixedUpdate depending on if rigidbodies are used for movement or not.

override void	OnDisable ()

override int	OnUpgradeSerializedData (int version, bool unityThread)
	Handle serialization backwards compatibility.

Protected Member Functions inherited from AIBase
	AIBase ()

void	ApplyGravity (float deltaTime)
	Accelerates the agent downwards.

override void	Awake ()
	Initializes reference variables.

Vector2	CalculateDeltaToMoveThisFrame (Vector2 position, float distanceToEndOfPath, float deltaTime)
	Calculates how far to move during a single frame.

virtual void	CalculatePathRequestEndpoints (out Vector3 start, out Vector3 end)
	Outputs the start point and end point of the next automatic path request.

void	CancelCurrentPathRequest ()

virtual void	FixedUpdate ()
	Called every physics update.

virtual void	OnDrawGizmos ()

virtual void	OnEnable ()
	Called when the component is enabled.

Vector3	RaycastPosition (Vector3 position, float lastElevation)
	Checks if the character is grounded and prevents ground penetration.

IEnumerator	RepeatTrySearchPath ()
	Tries to search for a path every repathRate seconds.

virtual void	RotateTowards (Vector2 direction, float maxDegrees)
	Rotates towards the specified direction.

virtual void	Start ()
	Starts searching for paths.

virtual void	Update ()
	Called every frame.

void	UpdateVelocity (Vector3 position)

Protected Attributes
PathInterpolator	interpolator = new PathInterpolator()
	Helper which calculates points along the current path.

Path	path
	Current path which is followed.

Protected Attributes inherited from AIBase
CharacterController	controller
	Cached CharacterController component.

Vector3	lastDeltaPosition
	Amount which the character wants or tried to move with during the last frame.

float	lastDeltaTime
	Delta time used for movement during the last frame.

float	lastRepath = float.NegativeInfinity
	Time when the last path request was started.

Vector3	prevPosition1
	Position of the character at the end of the last frame.

Vector3	prevPosition2
	Position of the character at the end of the frame before the last frame.

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 (does not include local avoidance and physics).

float	verticalVelocity
	Velocity due to gravity.

bool	waitingForPathCalculation = false
	Only when the previous path has been calculated should the script consider searching for a new path.

Properties
bool IAstarAI.	canMove `[get, set]`
	Enables or disables movement completely.

bool IAstarAI.	canSearch `[get, set]`
	Enables or disables recalculating the path at regular intervals.

bool	hasPath `[get]`
	True if this agent currently has a path that it follows.

float IAstarAI.	maxSpeed `[get, set]`
	Max speed in world units per second.

bool	pathPending `[get]`
	True if a path is currently being calculated.

Vector3 IAstarAI.	position `[get]`
	Position of the agent.

float	remainingDistance `[get]`
	Remaining distance along the current path to the destination.

float	speed `[get, set]`
	Maximum speed in world units per second.

Vector3	steeringTarget `[get]`
	Point on the path which the agent is currently moving towards.

Vector3	targetDirection `[get]`
	Direction that the agent wants to move in (excluding physics and local avoidance).

bool	TargetReached `[get]`
	True if the end of the path has been reached.

bool	targetReached `[get, set]`
	True if the agent has reached the end of the current path.

float	turningSpeed `[get, set]`
	Rotation speed.

Properties inherited from AIBase
Vector3	desiredVelocity `[get]`
	Velocity that this agent wants to move with.

Vector3	destination `[get, set]`
	Position in the world that this agent should move to.

bool	isStopped `[get, set]`
	Gets or sets if the agent should stop moving.

System.Action	onSearchPath `[get, set]`

virtual bool	shouldRecalculatePath `[get]`
	True if the path should be automatically recalculated as soon as possible.

Transform	target `[get, set]`
	Target to move towards.

bool	usingGravity `[get, set]`
	Indicates if gravity is used during this frame.

Vector3	velocity `[get]`
	Actual velocity that the agent is moving with.

Private Member Functions
Vector3 IAstarAIMovement.	ClampToNavmesh (Vector3 position, out bool positionChanged)
	Clamps the agent's position to the navmesh.

void IAstarAIMovement.	Move (Vector3 position, Vector3 deltaPosition)
	Move the agent.

void IAstarAIMovement.	RotateTowards (Vector3 direction, float maxDegrees)
	Rotates towards the specified direction.

void IAstarAIMovement.	UpdateVelocity (Vector3 position)
	To be called after all movement is done with the position of the agent.

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

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.

Vector3 IAstarAIMovement. ClampToNavmesh	(	Vector3	position,
		out bool	positionChanged
	)

privatevirtual

Clamps the agent's position to the navmesh.

Parameters

position	Position of the agent.
positionChanged	True if the agent's position had to be modified.

Returns: New position of the agent that has been clamped to the navmesh.

Note: This will not update the position of the agent's Transform component. It is assumed that the caller will do that later.

Reimplemented from AIBase.

void IAstarAIMovement. Move	(	Vector3	position,
		Vector3	deltaPosition
	)

privatevirtual

Move the agent.

Parameters

position	Position of the agent.
deltaPosition	Direction and distance to move the agent in world space.

Reimplemented from AIBase.

override void MovementUpdateInternal ( float deltaTime )

protectedvirtual

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

Implements AIBase.

override void OnDisable ( )

protectedvirtual

Reimplemented from AIBase.

override void OnPathComplete ( Path newPath )

virtual

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.

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.

Reimplemented in MineBotAI.

override int OnUpgradeSerializedData	(	int	version,
		bool	unityThread
	)

protectedvirtual

Handle serialization backwards compatibility.

Reimplemented from AIBase.

void IAstarAIMovement. RotateTowards	(	Vector3	direction,
		float	maxDegrees
	)

private

Rotates towards the specified direction.

Parameters

direction	Direction rotate towards.
maxDegrees	Maximum number of degrees to rotate this frame.

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.

void IAstarAIMovement. UpdateVelocity ( Vector3 position )

private

To be called after all movement is done with the position of the agent.

Parameters

position Current position of the agent (as a parameter mostly for performance reasons as reading from transform.position can be slow).

You have to call this if you are handling movement manually to make sure e.g the velocity field is up to date.This is automatically called by the Move method, so if you are using that method this should not be called.

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.

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

Helper which calculates points along the current path.

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 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

bool slowWhenNotFacingTarget = true

Slow down when not facing the target direction.

Incurs at a small performance overhead.

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

Property Documentation

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.

See Also: canSearch; isStopped

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

bool hasPath

get

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

float IAstarAI. maxSpeed

getsetprivate

Max speed in world units per second.

bool pathPending

get

True if a path is currently being calculated.

Vector3 IAstarAI. position

getprivate

Position of the agent.

In world space.

See Also: Teleport

float remainingDistance

get

Remaining distance along the current path to the destination.

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.

float speed

getset

Maximum speed in world units per second.

Deprecated:: Use maxSpeed instead

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.

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.

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 targetReached (lowercase t)

bool targetReached

getset

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

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.

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

Detailed Description

Quick overview of the variables

Public Member Functions

Public Attributes

Protected Member Functions

Protected Attributes

Properties

Private Member Functions

Additional Inherited Members

Member Function Documentation

Member Data Documentation

Property Documentation