Class AStar3D

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

Inheritance: RefCounted

Object

AStar3D

Remarks

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 AStar3D.add_point and create segments manually with AStar3D.connect_points. Once done, you can test if there is a path between two points with the AStar3D.are_points_connected function, get a path containing indices by AStar3D.get_id_path, or one containing actual coordinates with AStar3D.get_point_path.

It is also possible to use non-Euclidean distances. To do so, create a script that extends AStar3D and override the methods AStar3D._compute_cost and AStar3D._estimate_cost. Both should take two point IDs and return the distance between the corresponding points.

Example: Use Manhattan distance instead of Euclidean distance:

gdscript
C#

class_name MyAStar3D
extends AStar3D

func _compute_cost(u, v):
    var u_pos = get_point_position(u)
    var v_pos = get_point_position(v)
    return abs(u_pos.x - v_pos.x) + abs(u_pos.y - v_pos.y) + abs(u_pos.z - v_pos.z)

func _estimate_cost(u, v):
    var u_pos = get_point_position(u)
    var v_pos = get_point_position(v)
    return abs(u_pos.x - v_pos.x) + abs(u_pos.y - v_pos.y) + abs(u_pos.z - v_pos.z)

using Godot;

[GlobalClass]
public partial class MyAStar3D : AStar3D
{
    public override float _ComputeCost(long fromId, long toId)
    {
        Vector3 fromPoint = GetPointPosition(fromId);
        Vector3 toPoint = GetPointPosition(toId);

        return Mathf.Abs(fromPoint.X - toPoint.X) + Mathf.Abs(fromPoint.Y - toPoint.Y) + Mathf.Abs(fromPoint.Z - toPoint.Z);
    }

    public override float _EstimateCost(long fromId, long toId)
    {
        Vector3 fromPoint = GetPointPosition(fromId);
        Vector3 toPoint = GetPointPosition(toId);
        return Mathf.Abs(fromPoint.X - toPoint.X) + Mathf.Abs(fromPoint.Y - toPoint.Y) + Mathf.Abs(fromPoint.Z - toPoint.Z);

    }

}

AStar3D._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 AStar3D._compute_cost might be computation-heavy. If this is not the case, make AStar3D._estimate_cost return the same value as AStar3D._compute_cost to provide the algorithm with the most accurate information.

If the default AStar3D._estimate_cost and AStar3D._compute_cost methods are used, or if the supplied AStar3D._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 AStar3D._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

_compute_cost(int, int)

Qualifiers: virtualconst

Called when computing the cost between two connected points.

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

float _compute_cost(int from_id, int to_id)

Parameters

from_id int
to_id int

_estimate_cost(int, int)

Qualifiers: virtualconst

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.

float _estimate_cost(int from_id, int end_id)

Parameters

from_id int
end_id int

add_point(int, Vector3, float)

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 AStar3D._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.

gdscript
C#

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

var astar = new AStar3D();
astar.AddPoint(1, new 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.

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

Parameters

id int
position Vector3
weight_scale float

are_points_connected(int, int, bool)

Qualifiers: const

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.

bool are_points_connected(int id, int to_id, bool bidirectional)

Parameters

id int
to_id int
bidirectional bool

clear

Clears all the points and segments.

void clear

connect_points(int, int, bool)

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

gdscript
C#

var astar = AStar3D.new()
astar.add_point(1, Vector3(1, 1, 0))
astar.add_point(2, Vector3(0, 5, 0))
astar.connect_points(1, 2, false)

var astar = new AStar3D();
astar.AddPoint(1, new Vector3(1, 1, 0));
astar.AddPoint(2, new Vector3(0, 5, 0));
astar.ConnectPoints(1, 2, false);

void connect_points(int id, int to_id, bool bidirectional)

Parameters

id int
to_id int
bidirectional bool

disconnect_points(int, int, bool)

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.

void disconnect_points(int id, int to_id, bool bidirectional)

Parameters

id int
to_id int
bidirectional bool

get_available_point_id

Qualifiers: const

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

int get_available_point_id

get_closest_point(Vector3, bool)

Qualifiers: const

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.

int get_closest_point(Vector3 to_position, bool include_disabled)

Parameters

to_position Vector3
include_disabled bool

get_closest_position_in_segment(Vector3)

Qualifiers: const

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

gdscript
C#

var astar = AStar3D.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)

var astar = new AStar3D();
astar.AddPoint(1, new Vector3(0, 0, 0));
astar.AddPoint(2, new Vector3(0, 5, 0));
astar.ConnectPoints(1, 2);
Vector3 res = astar.GetClosestPositionInSegment(new 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.

Vector3 get_closest_position_in_segment(Vector3 to_position)

Parameters

to_position Vector3

get_id_path(int, int, bool)

Returns an array with the IDs of the points that form the path found by AStar3D between the given points. The array is ordered from the starting point to the ending point of the path.

If there is no valid path to the target, and allow_partial_path is true, returns a path to the point closest to the target that can be reached.

Note: When allow_partial_path is true and to_id is disabled the search may take an unusually long time to finish.

gdscript
C#

var astar = AStar3D.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]

var astar = new AStar3D();
astar.AddPoint(1, new Vector3(0, 0, 0));
astar.AddPoint(2, new Vector3(0, 1, 0), 1); // Default weight is 1
astar.AddPoint(3, new Vector3(1, 1, 0));
astar.AddPoint(4, new Vector3(2, 0, 0));
astar.ConnectPoints(1, 2, false);
astar.ConnectPoints(2, 3, false);
astar.ConnectPoints(4, 3, false);
astar.ConnectPoints(1, 4, false);
long[] res = astar.GetIdPath(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.

PackedInt64Array get_id_path(int from_id, int to_id, bool allow_partial_path)

Parameters

from_id int
to_id int
allow_partial_path bool

get_point_capacity

Qualifiers: const

Returns the capacity of the structure backing the points, useful in conjunction with AStar3D.reserve_space.

int get_point_capacity

get_point_connections(int)

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

gdscript
C#

var astar = AStar3D.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]

var astar = new AStar3D();
astar.AddPoint(1, new Vector3(0, 0, 0));
astar.AddPoint(2, new Vector3(0, 1, 0));
astar.AddPoint(3, new Vector3(1, 1, 0));
astar.AddPoint(4, new Vector3(2, 0, 0));
astar.ConnectPoints(1, 2, true);
astar.ConnectPoints(1, 3, true);

long[] neighbors = astar.GetPointConnections(1); // Returns [2, 3]

PackedInt64Array get_point_connections(int id)

Parameters

id int

get_point_count

Qualifiers: const

Returns the number of points currently in the points pool.

int get_point_count

get_point_ids

Returns an array of all point IDs.

PackedInt64Array get_point_ids

get_point_path(int, int, bool)

Returns an array with the points that are in the path found by AStar3D between the given points. The array is ordered from the starting point to the ending point of the path.

If there is no valid path to the target, and allow_partial_path is true, returns a path to the point closest to the target that can be reached.

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

Additionally, when allow_partial_path is true and to_id is disabled the search may take an unusually long time to finish.

PackedVector3Array get_point_path(int from_id, int to_id, bool allow_partial_path)

Parameters

from_id int
to_id int
allow_partial_path bool

get_point_position(int)

Qualifiers: const

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

Vector3 get_point_position(int id)

Parameters

id int

get_point_weight_scale(int)

Qualifiers: const

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

float get_point_weight_scale(int id)

Parameters

id int

has_point(int)

Qualifiers: const

Returns whether a point associated with the given id exists.

bool has_point(int id)

Parameters

id int

is_point_disabled(int)

Qualifiers: const

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

bool is_point_disabled(int id)

Parameters

id int

remove_point(int)

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

void remove_point(int id)

Parameters

id int

reserve_space(int)

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

void reserve_space(int num_nodes)

Parameters

num_nodes int

set_point_disabled(int, bool)

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

void set_point_disabled(int id, bool disabled)

Parameters

id int
disabled bool

set_point_position(int, Vector3)

Sets the position for the point with the given id.

void set_point_position(int id, Vector3 position)

Parameters

id int
position Vector3

set_point_weight_scale(int, float)

Sets the weight_scale for the point with the given id. The weight_scale is multiplied by the result of AStar3D._compute_cost when determining the overall cost of traveling across a segment from a neighboring point to this point.

void set_point_weight_scale(int id, float weight_scale)

Parameters

id int
weight_scale float

Table of Contents

Class AStar3D

Remarks

Methods

_compute_cost(int, int)

Parameters

_estimate_cost(int, int)

Parameters

add_point(int, Vector3, float)

Parameters

are_points_connected(int, int, bool)

Parameters

clear

connect_points(int, int, bool)

Parameters

disconnect_points(int, int, bool)

Parameters

get_available_point_id

get_closest_point(Vector3, bool)

Parameters

get_closest_position_in_segment(Vector3)

Parameters

get_id_path(int, int, bool)

Parameters

get_point_capacity

get_point_connections(int)

Parameters

get_point_count

get_point_ids

get_point_path(int, int, bool)

Parameters

get_point_position(int)

Parameters

get_point_weight_scale(int)

Parameters

has_point(int)

Parameters

is_point_disabled(int)

Parameters

remove_point(int)

Parameters

reserve_space(int)

Parameters

set_point_disabled(int, bool)

Parameters

set_point_position(int, Vector3)

Parameters

set_point_weight_scale(int, float)

Parameters