A* Pathfinding Project  4.0.7
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LegacyAIPath 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 is not written for high performance, so I do not recommend using it for large groups of units.

This script will try to follow a target transform, in regular intervals, the path to that target will be recalculated. It will on FixedUpdate try to move towards the next point in the path. However it will only move in the forward direction, but it will rotate around it's Y-axis to make it 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 turningSpeed, however slowdownDistance might require some explanation. It is the approximate distance from the target 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 forwardLook and pickNextWaypointDist to a higher value than this.
pickNextWaypointDist is simply determines within what range it will switch to target the next waypoint in the path.
forwardLook will try to calculate an interpolated target point on the current segment in the path so that it has a distance of forwardLook from the AI
Below is an image illustrating several variables as well as some internal ones, but which are relevant for understanding how it works. Note that the forwardLook range will not match up exactly with the target point practically, even though that's the goal.

This script has many movement fallbacks. If it finds a NavmeshController, it will use that, otherwise it will look for a character controller, then for a rigidbody and if it hasn't been able to find any it will use Transform.Translate which is guaranteed to always work.

Use the AIPath class instead. This class only exists for compatibility reasons.

Public Member Functions

override void OnPathComplete (Path _p)
 Called when a requested path has finished calculation.
- Public Member Functions inherited from AIPath
Vector3 CalculateVelocity (Vector3 position)
 Current desired velocity of the agent (excluding physics and local avoidance but it includes gravity).
virtual Vector3 GetFeetPosition ()
void OnDisable ()
virtual void OnTargetReached ()
virtual void SearchPath ()
 Requests a path to the target.
float TrySearchPath ()
 Tries to search for a path.

Public Attributes

bool closestOnPathCheck = true
 Do a closest point on path check when receiving path callback.
float forwardLook = 1
 Target point is Interpolated on the current segment in the path so that it has a distance of forwardLook from the AI.
- Public Attributes inherited from AIPath
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 Awake ()
 Initializes reference variables.
Vector3 CalculateTargetPoint (Vector3 p, Vector3 a, Vector3 b)
 Calculates target point from the current line segment.
new Vector3 CalculateVelocity (Vector3 currentPosition)
 Calculates desired velocity.
void RotateTowards (Vector3 dir)
 Rotates in the specified direction.
override void Update ()
 Called every frame.
float XZSqrMagnitude (Vector3 a, Vector3 b)
- Protected Member Functions inherited from AIPath
override void MovementUpdate (float deltaTime)
 Called during either Update or FixedUpdate depending on if rigidbodies are used for movement or not.
virtual void OnEnable ()
 Called when the component is enabled.
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)
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.

Protected Attributes

int currentWaypointIndex = 0
 Current index in the path which is current target.
Vector3 lastFoundWaypointPosition
float lastFoundWaypointTime = -9999
float minMoveScale = 0.05F
new Vector3 targetDirection
 Relative direction to where the AI is heading.
- Protected Attributes inherited from AIPath
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.

Additional Inherited Members

- Static Protected Attributes inherited from AIBase
static readonly Color GizmoColorRaycast = new Color(118.0f/255, 206.0f/255, 112.0f/255)
- Properties inherited from AIPath
Vector3 targetDirection [get]
 Direction that the agent wants to move in (excluding physics and local avoidance).
bool TargetReached [get, set]
 True if the end of the path has been reached.
float turningSpeed [get, set]
 Rotation speed.

Member Function Documentation

override void Awake ( )

Initializes reference variables.

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

Reimplemented from AIBase.

Vector3 CalculateTargetPoint ( Vector3  p,
Vector3  a,
Vector3  b 

Calculates target point from the current line segment.

pCurrent position
aLine segment start
bLine segment end The returned point will lie somewhere on the line segment.
See Also
This function uses .magnitude quite a lot, can it be optimized?
new Vector3 CalculateVelocity ( Vector3  currentPosition)

Calculates desired velocity.

Finds the target path segment and returns the forward direction, scaled with speed. A whole bunch of restrictions on the velocity is applied to make sure it doesn't overshoot, does not look too far ahead, and slows down when close to the target. /see speed /see endReachedDistance /see slowdownDistance /see CalculateTargetPoint /see targetPoint /see targetDirection /see currentWaypointIndex

override void OnPathComplete ( Path  _p)

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 from AIPath.

void RotateTowards ( Vector3  dir)

Rotates in the specified direction.

Rotates around the Y-axis.

See Also
override void Update ( )

Called every frame.

If no rigidbodies are used then all movement happens here

Reimplemented from AIBase.

float XZSqrMagnitude ( Vector3  a,
Vector3  b 

Member Data Documentation

bool closestOnPathCheck = true

Do a closest point on path check when receiving path callback.

Usually the AI has moved a bit between requesting the path, and getting it back, and there is usually a small gap between the AI and the closest node. If this option is enabled, it will simulate, when the path callback is received, movement between the closest node and the current AI position. This helps to reduce the moments when the AI just get a new path back, and thinks it ought to move backwards to the start of the new path even though it really should just proceed forward.

int currentWaypointIndex = 0

Current index in the path which is current target.

float forwardLook = 1

Target point is Interpolated on the current segment in the path so that it has a distance of forwardLook from the AI.

See the detailed description of AIPath for an illustrative image

Vector3 lastFoundWaypointPosition
float lastFoundWaypointTime = -9999
float minMoveScale = 0.05F
new Vector3 targetDirection

Relative direction to where the AI is heading.

Filled in by CalculateVelocity

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