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AStar3D

Inherits: RefCounted < Object

An implementation of A* for finding the shortest path between two vertices on a connected graph in 3D space.

Description

A* (A star) is a computer algorithm 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 3D space and Euclidean distances by default.

You must add points manually with add_point and create segments manually with connect_points. Once done, you can test if there is a path between two points with the are_points_connected function, get a path containing indices by get_id_path, or one containing actual coordinates with get_point_path.

It is also possible to use non-Euclidean distances. To do so, create a class that extends AStar3D and override methods _compute_cost and _estimate_cost. Both take two indices and return a length, as is shown in the following example.

class MyAStar:
    extends AStar3D

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

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

_estimate_cost 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 _estimate_cost return the same value as _compute_cost to provide the algorithm with the most accurate information.

If the default _estimate_cost and _compute_cost methods are used, or if the supplied _estimate_cost 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 the sum of the _compute_cost results of all segments in the path multiplied by the weight_scales of the endpoints 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 the sum of Euclidean distances of all segments in the path.

Methods

float

_compute_cost ( int from_id, int to_id ) virtual const

float

_estimate_cost ( int from_id, int to_id ) virtual const

void

add_point ( int id, Vector3 position, float weight_scale=1.0 )

bool

are_points_connected ( int id, int to_id, bool bidirectional=true ) const

void

clear ( )

void

connect_points ( int id, int to_id, bool bidirectional=true )

void

disconnect_points ( int id, int to_id, bool bidirectional=true )

int

get_available_point_id ( ) const

int

get_closest_point ( Vector3 to_position, bool include_disabled=false ) const

Vector3

get_closest_position_in_segment ( Vector3 to_position ) const

PackedInt64Array

get_id_path ( int from_id, int to_id )

int

get_point_capacity ( ) const

PackedInt64Array

get_point_connections ( int id )

int

get_point_count ( ) const

PackedInt64Array

get_point_ids ( )

PackedVector3Array

get_point_path ( int from_id, int to_id )

Vector3

get_point_position ( int id ) const

float

get_point_weight_scale ( int id ) const

bool

has_point ( int id ) const

bool

is_point_disabled ( int id ) const

void

remove_point ( int id )

void

reserve_space ( int num_nodes )

void

set_point_disabled ( int id, bool disabled=true )

void

set_point_position ( int id, Vector3 position )

void

set_point_weight_scale ( int id, float weight_scale )


Method Descriptions

float _compute_cost ( int from_id, int to_id ) virtual const

Called when computing the cost between two connected points.

Note that this function is hidden in the default AStar3D class.


float _estimate_cost ( int from_id, int to_id ) virtual const

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

Note that this function is hidden in the default AStar3D class.


void add_point ( int id, Vector3 position, float weight_scale=1.0 )

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 0.0 or greater.

The weight_scale is multiplied by the result of _compute_cost 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 = AStar3D.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