Documentation
¶
Overview ¶
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 AddPoint and create segments manually with ConnectPoints. Once done, you can test if there is a path between two points with the ArePointsConnected function, get a path containing indices by GetIdPath, or one containing actual coordinates with GetPointPath.
It is also possible to use non-Euclidean distances. To do so, create a script that extends AStar3D and override the methods ComputeCost and EstimateCost. Both should take two point IDs and return the distance between the corresponding points.
Example: Use Manhattan distance instead of Euclidean distance:
package main
import (
"graphics.gd/classdb/AStar3D"
"graphics.gd/variant/Float"
)
type MyAStar3D struct {
AStar3D.Extension[MyAStar3D]
}
func (astar *MyAStar3D) ComputeCost(u, v AStar3D.Point) Float.X {
var u_pos = astar.AsAStar3D().GetPointPosition(u)
var v_pos = astar.AsAStar3D().GetPointPosition(v)
return Float.Abs(u_pos.X-v_pos.X) + Float.Abs(u_pos.Y-v_pos.Y) + Float.Abs(u_pos.Z-v_pos.Z)
}
func (astar *MyAStar3D) EstimateCost(u, v AStar3D.Point) Float.X {
var u_pos = astar.AsAStar3D().GetPointPosition(u)
var v_pos = astar.AsAStar3D().GetPointPosition(v)
return Float.Abs(u_pos.X-v_pos.X) + Float.Abs(u_pos.Y-v_pos.Y) + Float.Abs(u_pos.Z-v_pos.Z)
}
EstimateCost 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 ComputeCost might be computation-heavy. If this is not the case, make EstimateCost return the same value as ComputeCost to provide the algorithm with the most accurate information.
If the default EstimateCost and ComputeCost methods are used, or if the supplied EstimateCost 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 ComputeCost 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.
Index ¶
- type Advanced
- type Any
- type Expanded
- type Extension
- type ID
- type Implementation
- type Instance
- func (self Instance) AddPoint(id Point, position Vector3.XYZ)
- func (self Instance) ArePointsConnected(id Point, to_id Point) bool
- func (self Instance) AsAStar3D() Instance
- func (self Instance) AsObject() [1]gd.Object
- func (self Instance) AsRefCounted() [1]gd.RefCounted
- func (self Instance) Clear()
- func (self Instance) ConnectPoints(id Point, to_id Point)
- func (self Instance) DisconnectPoints(id Point, to_id Point)
- func (self Instance) GetAvailablePointId() int
- func (self Instance) GetClosestPoint(to_position Vector3.XYZ) int
- func (self Instance) GetClosestPositionInSegment(to_position Vector3.XYZ) Vector3.XYZ
- func (self Instance) GetIdPath(from_id Point, to_id Point) []Point
- func (self Instance) GetPointCapacity() int
- func (self Instance) GetPointConnections(id Point) []Point
- func (self Instance) GetPointCount() int
- func (self Instance) GetPointIds() []Point
- func (self Instance) GetPointPath(from_id Point, to_id Point) []Vector3.XYZ
- func (self Instance) GetPointPosition(id Point) Vector3.XYZ
- func (self Instance) GetPointWeightScale(id Point) Float.X
- func (self Instance) HasPoint(id Point) bool
- func (self Instance) ID() ID
- func (self Instance) IsPointDisabled(id Point) bool
- func (self Instance) MoreArgs() MoreArgs
- func (self Instance) NeighborFilterEnabled() bool
- func (self Instance) RemovePoint(id Point)
- func (self Instance) ReserveSpace(num_nodes int)
- func (self Instance) SetNeighborFilterEnabled(value bool)
- func (self *Instance) SetObject(obj [1]gd.Object) bool
- func (self Instance) SetPointDisabled(id Point)
- func (self Instance) SetPointPosition(id Point, position Vector3.XYZ)
- func (self Instance) SetPointWeightScale(id Point, weight_scale Float.X)
- func (self Instance) Virtual(name string) reflect.Value
- type Interface
- type MoreArgs
- func (self MoreArgs) AddPoint(id Point, position Vector3.XYZ, weight_scale Float.X)
- func (self MoreArgs) ArePointsConnected(id Point, to_id Point, bidirectional bool) bool
- func (self MoreArgs) ConnectPoints(id Point, to_id Point, bidirectional bool)
- func (self MoreArgs) DisconnectPoints(id Point, to_id Point, bidirectional bool)
- func (self MoreArgs) GetClosestPoint(to_position Vector3.XYZ, include_disabled bool) int
- func (self MoreArgs) GetIdPath(from_id Point, to_id Point, allow_partial_path bool) []Point
- func (self MoreArgs) GetPointPath(from_id Point, to_id Point, allow_partial_path bool) []Vector3.XYZ
- func (self MoreArgs) SetPointDisabled(id Point, disabled bool)
- type Point
Constants ¶
This section is empty.
Variables ¶
This section is empty.
Functions ¶
This section is empty.
Types ¶
type Advanced ¶
type Advanced = class
Advanced exposes a 1:1 low-level instance of the class, undocumented, for those who know what they are doing.
type Extension ¶
Extension can be embedded in a new struct to create an extension of this class. T should be the type that is embedding this [Extension]See Interface for methods that can be overridden by T.
func (*Extension[T]) AsRefCounted ¶
func (self *Extension[T]) AsRefCounted() [1]gd.RefCounted
type ID ¶
ID is a typed object ID (reference) to an instance of this class, use it to store references to objects with unknown lifetimes, as an ID will not panic on use if the underlying object has been destroyed.
type Implementation ¶
type Implementation = implementation
Implementation implements Interface with empty methods.
type Instance ¶
Instance of the class with convieniently typed arguments and results.
var Nil Instance
Nil is a nil/null instance of the class. Equivalent to the zero value.
func (Instance) AddPoint ¶
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 ComputeCost 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_scale's to form a path.
If there already exists a point for the given 'id', its position and weight scale are updated to the given values.
func (Instance) ArePointsConnected ¶
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.
func (Instance) AsRefCounted ¶
func (self Instance) AsRefCounted() [1]gd.RefCounted
func (Instance) ConnectPoints ¶
Creates a segment between the given points. If 'bidirectional' is false, only movement from 'id' to 'to_id' is allowed, not the reverse direction.
func (Instance) DisconnectPoints ¶
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.
func (Instance) GetAvailablePointId ¶
Returns the next available point ID with no point associated to it.
func (Instance) GetClosestPoint ¶
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.
func (Instance) GetClosestPositionInSegment ¶
Returns the closest position to 'to_position' that resides inside a segment between two connected points.
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.
func (Instance) GetIdPath ¶
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.
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.
func (Instance) GetPointCapacity ¶
Returns the capacity of the structure backing the points, useful in conjunction with ReserveSpace.
func (Instance) GetPointConnections ¶
Returns an array with the IDs of the points that form the connection with the given point.
func (Instance) GetPointCount ¶
Returns the number of points currently in the points pool.
func (Instance) GetPointIds ¶
Returns an array of all point IDs.
func (Instance) GetPointPath ¶
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; it can only be used from a single Thread at a given time. Consider using Mutex to ensure exclusive access to one thread to avoid race conditions.
Additionally, when 'allow_partial_path' is true and 'to_id' is disabled the search may take an unusually long time to finish.
func (Instance) GetPointPosition ¶
Returns the position of the point associated with the given 'id'.
func (Instance) GetPointWeightScale ¶
Returns the weight scale of the point associated with the given 'id'.
func (Instance) IsPointDisabled ¶
Returns whether a point is disabled or not for pathfinding. By default, all points are enabled.
func (Instance) MoreArgs ¶
MoreArgs enables certain functions to be called with additional 'optional' arguments.
func (Instance) NeighborFilterEnabled ¶
If true enables the filtering of neighbors via FilterNeighbor.
func (Instance) RemovePoint ¶
Removes the point associated with the given 'id' from the points pool.
func (Instance) ReserveSpace ¶
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.
func (Instance) SetNeighborFilterEnabled ¶
SetNeighborFilterEnabled sets the property returned by [IsNeighborFilterEnabled].
func (Instance) SetPointDisabled ¶
Disables or enables the specified point for pathfinding. Useful for making a temporary obstacle.
func (Instance) SetPointPosition ¶
Sets the 'position' for the point with the given 'id'.
func (Instance) SetPointWeightScale ¶
Sets the 'weight_scale' for the point with the given 'id'. The 'weight_scale' is multiplied by the result of ComputeCost when determining the overall cost of traveling across a segment from a neighboring point to this point.
type Interface ¶
type Interface interface {
// Called when neighboring point enters processing and if [NeighborFilterEnabled] is true. If true is returned the point will not be processed.
//
// Note that this function is hidden in the default [AStar3D] class.
//
// [AStar3D]: https://pkg.go.dev/graphics.gd/classdb/AStar3D
// [NeighborFilterEnabled]: https://pkg.go.dev/graphics.gd/classdb/AStar3D#Instance.NeighborFilterEnabled
FilterNeighbor(from_id Point, neighbor_id Point) bool
// 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.
//
// [AStar3D]: https://pkg.go.dev/graphics.gd/classdb/AStar3D
EstimateCost(from_id Point, end_id Point) Float.X
// Called when computing the cost between two connected points.
//
// Note that this function is hidden in the default [AStar3D] class.
//
// [AStar3D]: https://pkg.go.dev/graphics.gd/classdb/AStar3D
ComputeCost(from_id Point, to_id Point) Float.X
}
type MoreArgs ¶
MoreArgs is a container for Instance functions with additional 'optional' arguments.
func (MoreArgs) AddPoint ¶
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 ComputeCost 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_scale's to form a path.
If there already exists a point for the given 'id', its position and weight scale are updated to the given values.
func (MoreArgs) ArePointsConnected ¶
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.
func (MoreArgs) ConnectPoints ¶
Creates a segment between the given points. If 'bidirectional' is false, only movement from 'id' to 'to_id' is allowed, not the reverse direction.
func (MoreArgs) DisconnectPoints ¶
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.
func (MoreArgs) GetClosestPoint ¶
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.
func (MoreArgs) GetIdPath ¶
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.
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.
func (MoreArgs) GetPointPath ¶
func (self MoreArgs) GetPointPath(from_id Point, to_id Point, allow_partial_path bool) []Vector3.XYZ
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; it can only be used from a single Thread at a given time. Consider using Mutex to ensure exclusive access to one thread to avoid race conditions.
Additionally, when 'allow_partial_path' is true and 'to_id' is disabled the search may take an unusually long time to finish.
func (MoreArgs) SetPointDisabled ¶
Disables or enables the specified point for pathfinding. Useful for making a temporary obstacle.
Source Files