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AStar Class

A* (A star) is a computer algorithm that is widely used in pathfinding and graph traversal, the process of plotting short paths among vertices (points), passing through a given set of edges (segments). It enjoys widespread use due to its performance and accuracy. Godot's A* implementation uses points in three-dimensional space and Euclidean distances by default.

You must add points manually with AddPoint(Int32, Vector3, Single) and create segments manually with ConnectPoints(Int32, Int32, Boolean). Then you can test if there is a path between two points with the ArePointsConnected(Int32, Int32, Boolean) function, get a path containing indices by GetIdPath(Int32, Int32), or one containing actual coordinates with GetPointPath(Int32, Int32).

It is also possible to use non-Euclidean distances. To do so, create a class that extends AStar and override methods _ComputeCost(Int32, Int32) and _EstimateCost(Int32, Int32). Both take two indices and return a length, as is shown in the following example.

class MyAStar:
    extends AStar

    func _compute_cost(u, v):
        return abs(u - v)

    func _estimate_cost(u, v):
        return min(0, abs(u - v) - 1)

_EstimateCost(Int32, Int32) should return a lower bound of the distance, i.e. _estimate_cost(u, v) <= _compute_cost(u, v). This serves as a hint to the algorithm because the custom _compute_cost might be computation-heavy. If this is not the case, make _EstimateCost(Int32, Int32) return the same value as _ComputeCost(Int32, Int32) to provide the algorithm with the most accurate information.

If the default _EstimateCost(Int32, Int32) and _ComputeCost(Int32, Int32) methods are used, or if the supplied _EstimateCost(Int32, Int32) method returns a lower bound of the cost, then the paths returned by A* will be the lowest cost paths. Here, the cost of a path equals to the sum of the _ComputeCost(Int32, Int32) results of all segments in the path multiplied by the weight_scales of the end points of the respective segments. If the default methods are used and the weight_scales of all points are set to 1.0, then this equals to the sum of Euclidean distances of all segments in the path.

Inheritance Hierarchy

Namespace:  Godot
Assembly:  GodotSharp (in GodotSharp.dll) Version: 1.0.0
Syntax
C#
public class AStar : Reference

The AStar type exposes the following members.

Constructors
  NameDescription
Public methodAStar
Initializes a new instance of the AStar class
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Properties
  NameDescription
Public propertyDynamicObject
Gets a new DynamicGodotObject associated with this instance.
(Inherited from Object.)
Public propertyNativeInstance (Inherited from Object.)
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Methods
  NameDescription
Public method_ComputeCost

Called when computing the cost between two connected points.

Note that this function is hidden in the default AStar class.

Public method_EstimateCost

Called when estimating the cost between a point and the path's ending point.

Note that this function is hidden in the default AStar class.

Public method_Get

Virtual method which can be overridden to customize the return value of Get(String).

Returns the given property. Returns null if the property does not exist.

(Inherited from Object.)
Public method_GetPropertyList

Virtual method which can be overridden to customize the return value of GetPropertyList.

Returns the object's property list as an Array of dictionaries.

Each property's Dictionary must contain at least name: String and type: int (see VariantType) entries. Optionally, it can also include hint: int (see PropertyHint), hint_string: String, and usage: int (see PropertyUsageFlags).

(Inherited from Object.)
Public method_Notification

Called whenever the object receives a notification, which is identified in what by a constant. The base Object has two constants and , but subclasses such as Node define a lot more notifications which are also received by this method.

(Inherited from Object.)
Public method_Set

Virtual method which can be overridden to customize the return value of Set(String, Object).

Sets a property. Returns true if the property exists.

(Inherited from Object.)
Public methodAddPoint

Adds a new point at the given position with the given identifier. The id must be 0 or larger, and the weight_scale must be 1 or larger.

The weight_scale is multiplied by the result of _ComputeCost(Int32, Int32) when determining the overall cost of traveling across a segment from a neighboring point to this point. Thus, all else being equal, the algorithm prefers points with lower weight_scales to form a path.

var astar = AStar.new()
astar.add_point(1, Vector3(1, 0, 0), 4) # Adds the point (1, 0, 0) with weight_scale 4 and id 1

If there already exists a point for the given id, its position and weight scale are updated to the given values.

Public methodAddUserSignal

Adds a user-defined signal. Arguments are optional, but can be added as an Array of dictionaries, each containing name: String and type: int (see VariantType) entries.

(Inherited from Object.)
Public methodArePointsConnected

Returns whether the two given points are directly connected by a segment. If bidirectional is false, returns whether movement from id to to_id is possible through this segment.

Public methodCall

Calls the method on the object and returns the result. This method supports a variable number of arguments, so parameters are passed as a comma separated list. Example:

call("set", "position", Vector2(42.0, 0.0))

Note: In C#, the method name must be specified as snake_case if it is defined by a built-in Godot node. This doesn't apply to user-defined methods where you should use the same convention as in the C# source (typically PascalCase).

(Inherited from Object.)
Public methodCallDeferred

Calls the method on the object during idle time. This method supports a variable number of arguments, so parameters are passed as a comma separated list. Example:

call_deferred("set", "position", Vector2(42.0, 0.0))

Note: In C#, the method name must be specified as snake_case if it is defined by a built-in Godot node. This doesn't apply to user-defined methods where you should use the same convention as in the C# source (typically PascalCase).

(Inherited from Object.)
Public methodCallv

Calls the method on the object and returns the result. Contrarily to Call(String, Object), this method does not support a variable number of arguments but expects all parameters to be via a single Array.

callv("set", [ "position", Vector2(42.0, 0.0) ])

(Inherited from Object.)
Public methodCanTranslateMessages

Returns true if the object can translate strings. See SetMessageTranslation(Boolean) and Tr(String).

(Inherited from Object.)
Public methodClear

Clears all the points and segments.

Public methodConnect

Connects a signal to a method on a target object. Pass optional binds to the call as an Array of parameters. These parameters will be passed to the method after any parameter used in the call to EmitSignal(String, Object). Use flags to set deferred or one-shot connections. See ObjectConnectFlags constants.

A signal can only be connected once to a method. It will throw an error if already connected, unless the signal was connected with . To avoid this, first, use IsConnected(String, Object, String) to check for existing connections.

If the target is destroyed in the game's lifecycle, the connection will be lost.

Examples:

connect("pressed", self, "_on_Button_pressed") # BaseButton signal
connect("text_entered", self, "_on_LineEdit_text_entered") # LineEdit signal
connect("hit", self, "_on_Player_hit", [ weapon_type, damage ]) # User-defined signal

An example of the relationship between binds passed to Connect(String, Object, String, Array, UInt32) and parameters used when calling EmitSignal(String, Object):

connect("hit", self, "_on_Player_hit", [ weapon_type, damage ]) # weapon_type and damage are passed last
emit_signal("hit", "Dark lord", 5) # "Dark lord" and 5 are passed first
func _on_Player_hit(hit_by, level, weapon_type, damage):
    print("Hit by %s (lvl %d) with weapon %s for %d damage" % [hit_by, level, weapon_type, damage])

(Inherited from Object.)
Public methodConnectPoints

Creates a segment between the given points. If bidirectional is false, only movement from id to to_id is allowed, not the reverse direction.

var astar = AStar.new()
astar.add_point(1, Vector3(1, 1, 0))
astar.add_point(2, Vector3(0, 5, 0))
astar.connect_points(1, 2, false)

Public methodDisconnect

Disconnects a signal from a method on the given target.

If you try to disconnect a connection that does not exist, the method will throw an error. Use IsConnected(String, Object, String) to ensure that the connection exists.

(Inherited from Object.)
Public methodDisconnectPoints

Deletes the segment between the given points. If bidirectional is false, only movement from id to to_id is prevented, and a unidirectional segment possibly remains.

Public methodDispose (Inherited from Object.)
Protected methodDispose(Boolean) (Inherited from Object.)
Public methodEmitSignal

Emits the given signal. The signal must exist, so it should be a built-in signal of this class or one of its parent classes, or a user-defined signal. This method supports a variable number of arguments, so parameters are passed as a comma separated list. Example:

emit_signal("hit", weapon_type, damage)
emit_signal("game_over")

(Inherited from Object.)
Public methodEquals (Inherited from Object.)
Protected methodFinalize (Inherited from Object.)
Public methodFree

Deletes the object from memory immediately. For Nodes, you may want to use QueueFree to queue the node for safe deletion at the end of the current frame.

Important: If you have a variable pointing to an object, it will not be assigned to null once the object is freed. Instead, it will point to a previously freed instance and you should validate it with @GDScript.is_instance_valid before attempting to call its methods or access its properties.

(Inherited from Object.)
Public methodGet

Returns the Variant value of the given property. If the property doesn't exist, this will return null.

Note: In C#, the property name must be specified as snake_case if it is defined by a built-in Godot node. This doesn't apply to user-defined properties where you should use the same convention as in the C# source (typically PascalCase).

(Inherited from Object.)
Public methodGetAvailablePointId

Returns the next available point ID with no point associated to it.

Public methodGetClass

Returns the object's class as a String.

(Inherited from Object.)
Public methodGetClosestPoint

Returns the ID of the closest point to to_position, optionally taking disabled points into account. Returns -1 if there are no points in the points pool.

Note: If several points are the closest to to_position, the one with the smallest ID will be returned, ensuring a deterministic result.

Public methodGetClosestPositionInSegment

Returns the closest position to to_position that resides inside a segment between two connected points.

var astar = AStar.new()
astar.add_point(1, Vector3(0, 0, 0))
astar.add_point(2, Vector3(0, 5, 0))
astar.connect_points(1, 2)
var res = astar.get_closest_position_in_segment(Vector3(3, 3, 0)) # Returns (0, 3, 0)

The result is in the segment that goes from y = 0 to y = 5. It's the closest position in the segment to the given point.

Public methodGetHashCode (Inherited from Object.)
Public methodGetIdPath

Returns an array with the IDs of the points that form the path found by AStar between the given points. The array is ordered from the starting point to the ending point of the path.

var astar = AStar.new()
astar.add_point(1, Vector3(0, 0, 0))
astar.add_point(2, Vector3(0, 1, 0), 1) # Default weight is 1
astar.add_point(3, Vector3(1, 1, 0))
astar.add_point(4, Vector3(2, 0, 0))

astar.connect_points(1, 2, false)
astar.connect_points(2, 3, false)
astar.connect_points(4, 3, false)
astar.connect_points(1, 4, false)

var res = astar.get_id_path(1, 3) # Returns [1, 2, 3]

If you change the 2nd point's weight to 3, then the result will be [1, 4, 3] instead, because now even though the distance is longer, it's "easier" to get through point 4 than through point 2.

Public methodGetIncomingConnections

Returns an Array of dictionaries with information about signals that are connected to the object.

Each Dictionary contains three String entries:

- source is a reference to the signal emitter.

- signal_name is the name of the connected signal.

- method_name is the name of the method to which the signal is connected.

(Inherited from Object.)
Public methodGetIndexed

Gets the object's property indexed by the given NodePath. The node path should be relative to the current object and can use the colon character (:) to access nested properties. Examples: "position:x" or "material:next_pass:blend_mode".

(Inherited from Object.)
Public methodGetInstanceId

Returns the object's unique instance ID.

This ID can be saved in EncodedObjectAsID, and can be used to retrieve the object instance with @GDScript.instance_from_id.

(Inherited from Object.)
Public methodGetMeta

Returns the object's metadata entry for the given name.

(Inherited from Object.)
Public methodGetMetaList

Returns the object's metadata as a String.

(Inherited from Object.)
Public methodGetMethodList

Returns the object's methods and their signatures as an Array.

(Inherited from Object.)
Public methodGetPointCapacity

Returns the capacity of the structure backing the points, useful in conjunction with reserve_space.

Public methodGetPointConnections

Returns an array with the IDs of the points that form the connection with the given point.

var astar = AStar.new()
astar.add_point(1, Vector3(0, 0, 0))
astar.add_point(2, Vector3(0, 1, 0))
astar.add_point(3, Vector3(1, 1, 0))
astar.add_point(4, Vector3(2, 0, 0))

astar.connect_points(1, 2, true)
astar.connect_points(1, 3, true)

var neighbors = astar.get_point_connections(1) # Returns [2, 3]

Public methodGetPointCount

Returns the number of points currently in the points pool.

Public methodGetPointPath

Returns an array with the points that are in the path found by AStar between the given points. The array is ordered from the starting point to the ending point of the path.

Note: This method is not thread-safe. If called from a Thread, it will return an empty Vector3 and will print an error message.

Public methodGetPointPosition

Returns the position of the point associated with the given id.

Public methodGetPoints

Returns an array of all points.

Public methodGetPointWeightScale

Returns the weight scale of the point associated with the given id.

Public methodGetPropertyList

Returns the object's property list as an Array of dictionaries.

Each property's Dictionary contain at least name: String and type: int (see VariantType) entries. Optionally, it can also include hint: int (see PropertyHint), hint_string: String, and usage: int (see PropertyUsageFlags).

(Inherited from Object.)
Public methodGetScript

Returns the object's Script instance, or null if none is assigned.

(Inherited from Object.)
Public methodGetSignalConnectionList

Returns an Array of connections for the given signal.

(Inherited from Object.)
Public methodGetSignalList

Returns the list of signals as an Array of dictionaries.

(Inherited from Object.)
Public methodGetType (Inherited from Object.)
Public methodHasMeta

Returns true if a metadata entry is found with the given name.

(Inherited from Object.)
Public methodHasMethod

Returns true if the object contains the given method.

(Inherited from Object.)
Public methodHasPoint

Returns whether a point associated with the given id exists.

Public methodHasSignal

Returns true if the given signal exists.

(Inherited from Object.)
Public methodHasUserSignal

Returns true if the given user-defined signal exists. Only signals added using AddUserSignal(String, Array) are taken into account.

(Inherited from Object.)
Public methodInitRef

Initializes the internal reference counter. Use this only if you really know what you are doing.

Returns whether the initialization was successful.

(Inherited from Reference.)
Public methodIsBlockingSignals

Returns true if signal emission blocking is enabled.

(Inherited from Object.)
Public methodIsClass

Returns true if the object inherits from the given class.

(Inherited from Object.)
Public methodIsConnected

Returns true if a connection exists for a given signal, target, and method.

(Inherited from Object.)
Public methodIsPointDisabled

Returns whether a point is disabled or not for pathfinding. By default, all points are enabled.

Public methodIsQueuedForDeletion (Inherited from Object.)
Protected methodMemberwiseClone (Inherited from Object.)
Public methodNotification

Send a given notification to the object, which will also trigger a call to the _Notification(Int32) method of all classes that the object inherits from.

If reversed is true, _Notification(Int32) is called first on the object's own class, and then up to its successive parent classes. If reversed is false, _Notification(Int32) is called first on the highest ancestor (Object itself), and then down to its successive inheriting classes.

(Inherited from Object.)
Public methodPropertyListChangedNotify

Notify the editor that the property list has changed, so that editor plugins can take the new values into account. Does nothing on export builds.

(Inherited from Object.)
Public methodReference_

Increments the internal reference counter. Use this only if you really know what you are doing.

Returns true if the increment was successful, false otherwise.

(Inherited from Reference.)
Public methodRemoveMeta

Removes a given entry from the object's metadata. See also SetMeta(String, Object).

(Inherited from Object.)
Public methodRemovePoint

Removes the point associated with the given id from the points pool.

Public methodReserveSpace

Reserves space internally for num_nodes points, useful if you're adding a known large number of points at once, for a grid for instance. New capacity must be greater or equals to old capacity.

Public methodSet

Assigns a new value to the given property. If the property does not exist, nothing will happen.

Note: In C#, the property name must be specified as snake_case if it is defined by a built-in Godot node. This doesn't apply to user-defined properties where you should use the same convention as in the C# source (typically PascalCase).

(Inherited from Object.)
Public methodSetBlockSignals

If set to true, signal emission is blocked.

(Inherited from Object.)
Public methodSetDeferred

Assigns a new value to the given property, after the current frame's physics step. This is equivalent to calling Set(String, Object) via CallDeferred(String, Object), i.e. call_deferred("set", property, value).

Note: In C#, the property name must be specified as snake_case if it is defined by a built-in Godot node. This doesn't apply to user-defined properties where you should use the same convention as in the C# source (typically PascalCase).

(Inherited from Object.)
Public methodSetIndexed

Assigns a new value to the property identified by the NodePath. The node path should be relative to the current object and can use the colon character (:) to access nested properties. Example:

set_indexed("position", Vector2(42, 0))
set_indexed("position:y", -10)
print(position) # (42, -10)

(Inherited from Object.)
Public methodSetMessageTranslation

Defines whether the object can translate strings (with calls to Tr(String)). Enabled by default.

(Inherited from Object.)
Public methodSetMeta

Adds, changes or removes a given entry in the object's metadata. Metadata are serialized and can take any Variant value.

To remove a given entry from the object's metadata, use RemoveMeta(String). Metadata is also removed if its value is set to null. This means you can also use set_meta("name", null) to remove metadata for "name".

(Inherited from Object.)
Public methodSetPointDisabled

Disables or enables the specified point for pathfinding. Useful for making a temporary obstacle.

Public methodSetPointPosition

Sets the position for the point with the given id.

Public methodSetPointWeightScale

Sets the weight_scale for the point with the given id. The weight_scale is multiplied by the result of _ComputeCost(Int32, Int32) when determining the overall cost of traveling across a segment from a neighboring point to this point.

Public methodSetScript

Assigns a script to the object. Each object can have a single script assigned to it, which are used to extend its functionality.

If the object already had a script, the previous script instance will be freed and its variables and state will be lost. The new script's method will be called.

(Inherited from Object.)
Public methodCode exampleToSignal
Returns a new SignalAwaiter awaiter configured to complete when the instance source emits the signal specified by the signal parameter.
(Inherited from Object.)
Public methodToString (Inherited from Object.)
Public methodTr

Translates a message using translation catalogs configured in the Project Settings.

Only works if message translation is enabled (which it is by default), otherwise it returns the message unchanged. See SetMessageTranslation(Boolean).

(Inherited from Object.)
Public methodUnreference

Decrements the internal reference counter. Use this only if you really know what you are doing.

Returns true if the decrement was successful, false otherwise.

(Inherited from Reference.)
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See Also