AStar2D

Inherits: RefCounted < Object

An implementation of A* for finding the shortest path between two vertices on a connected graph in 2D space.

Description

An implementation of the A* algorithm, used to find the shortest path between two vertices on a connected graph in 2D space.

See AStar3D for a more thorough explanation on how to use this class. AStar2D is a wrapper for AStar3D that enforces 2D coordinates.

Methods

Method Descriptions

float _compute_cost(from_id: int, to_id: int) virtual const 🔗

Called when computing the cost between two connected points.

Note that this function is hidden in the default AStar2D class.

float _estimate_cost(from_id: int, to_id: int) 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 AStar2D class.

void add_point(id: int, position: Vector2, weight_scale: float = 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.

GDScriptC#

var astar = AStar2D.new()
astar.add_point(1, Vector2(1, 0), 4) # Adds the point (1, 0) with weight_scale 4 and id 1

var astar = new AStar2D();
astar.AddPoint(1, new Vector2(1, 0), 4); // Adds the point (1, 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.

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

Returns whether there is a connection/segment between the given points. If bidirectional is false, returns whether movement from id to to_id is possible through this segment.

void clear() 🔗

Clears all the points and segments.

void connect_points(id: int, to_id: int, bidirectional: bool = true) 🔗

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

GDScriptC#

var astar = AStar2D.new()
astar.add_point(1, Vector2(1, 1))
astar.add_point(2, Vector2(0, 5))
astar.connect_points(1, 2, false)

var astar = new AStar2D();
astar.AddPoint(1, new Vector2(1, 1));
astar.AddPoint(2, new Vector2(0, 5));
astar.ConnectPoints(1, 2, false);

void disconnect_points(id: int, to_id: int, bidirectional: bool = true) 🔗

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.

int get_available_point_id() const 🔗

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

int get_closest_point(to_position: Vector2, include_disabled: bool = false) 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.

Vector2 get_closest_position_in_segment(to_position: Vector2) const 🔗

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

GDScriptC#

var astar = AStar2D.new()
astar.add_point(1, Vector2(0, 0))
astar.add_point(2, Vector2(0, 5))
astar.connect_points(1, 2)
var res = astar.get_closest_position_in_segment(Vector2(3, 3)) # Returns (0, 3)

var astar = new AStar2D();
astar.AddPoint(1, new Vector2(0, 0));
astar.AddPoint(2, new Vector2(0, 5));
astar.ConnectPoints(1, 2);
Vector2 res = astar.GetClosestPositionInSegment(new Vector2(3, 3)); // Returns (0, 3)

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.

PackedInt64Array get_id_path(from_id: int, to_id: int, allow_partial_path: bool = false) 🔗

Returns an array with the IDs of the points that form the path found by AStar2D 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.

GDScriptC#

var astar = AStar2D.new()
astar.add_point(1, Vector2(0, 0))
astar.add_point(2, Vector2(0, 1), 1) # Default weight is 1
astar.add_point(3, Vector2(1, 1))
astar.add_point(4, Vector2(2, 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 AStar2D();
astar.AddPoint(1, new Vector2(0, 0));
astar.AddPoint(2, new Vector2(0, 1), 1); // Default weight is 1
astar.AddPoint(3, new Vector2(1, 1));
astar.AddPoint(4, new Vector2(2, 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.

int get_point_capacity() const 🔗

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

PackedInt64Array get_point_connections(id: int) 🔗

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

GDScriptC#

var astar = AStar2D.new()
astar.add_point(1, Vector2(0, 0))
astar.add_point(2, Vector2(0, 1))
astar.add_point(3, Vector2(1, 1))
astar.add_point(4, Vector2(2, 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 AStar2D();
astar.AddPoint(1, new Vector2(0, 0));
astar.AddPoint(2, new Vector2(0, 1));
astar.AddPoint(3, new Vector2(1, 1));
astar.AddPoint(4, new Vector2(2, 0));
astar.ConnectPoints(1, 2, true);
astar.ConnectPoints(1, 3, true);
long[] neighbors = astar.GetPointConnections(1); // Returns [2, 3]

int get_point_count() const 🔗

Returns the number of points currently in the points pool.

PackedInt64Array get_point_ids() 🔗

Returns an array of all point IDs.

PackedVector2Array get_point_path(from_id: int, to_id: int, allow_partial_path: bool = false) 🔗

Returns an array with the points that are in the path found by AStar2D 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.

Vector2 get_point_position(id: int) const 🔗

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

float get_point_weight_scale(id: int) const 🔗

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

bool has_point(id: int) const 🔗

Returns whether a point associated with the given id exists.

bool is_point_disabled(id: int) const 🔗

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

void remove_point(id: int) 🔗

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

void reserve_space(num_nodes: 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 set_point_disabled(id: int, disabled: bool = true) 🔗

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

void set_point_position(id: int, position: Vector2) 🔗

Sets the position for the point with the given id.

void set_point_weight_scale(id: int, weight_scale: float) 🔗

Sets the weight_scale for the point with the given id. 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.

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