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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)
public partial class MyAStar : AStar3D
{
public override float _ComputeCost(long fromId, long toId)
{
return Mathf.Abs((int)(fromId - toId));
}
public override float _EstimateCost(long fromId, long toId)
{
return Mathf.Min(0, Mathf.Abs((int)(fromId - toId)) - 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¶
_compute_cost ( int from_id, int to_id ) virtual const |
|
_estimate_cost ( int from_id, int to_id ) virtual const |
|
void |
add_point ( int id, Vector3 position, float weight_scale=1.0 ) |