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Explain A Star pathfinding algorithm cost calcuation 

(cherry picked from commit f6634648ce)
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Maganty Rushyendra 2021-01-05 18:03:16 +08:00 committed by Rémi Verschelde
parent 66bfe855a8
commit 90d1d580af
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2 changed files with 7 additions and 4 deletions
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6
doc/classes/AStar.xml
View File

@ -18,6 +18,7 @@
return min(0, abs(u - v) - 1)
[/codeblock]
[method _estimate_cost] should return a lower bound of the distance, i.e. [code]_estimate_cost(u, v) <= _compute_cost(u, v)[/code]. This serves as a hint to the algorithm because the custom [code]_compute_cost[/code] might be computation-heavy. If this is not the case, make [method _estimate_cost] return the same value as [method _compute_cost] to provide the algorithm with the most accurate information.
If the default [method _estimate_cost] and [method _compute_cost] methods are used, or if the supplied [method _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 to the sum of the [method _compute_cost] results of all segments in the path multiplied by the [code]weight_scale[/code]s of the end points of the respective segments. If the default methods are used and the [code]weight_scale[/code]s of all points are set to [code]1.0[/code], then this equals to the sum of Euclidean distances of all segments in the path.
</description>
<tutorials>
</tutorials>
@ -56,7 +57,8 @@
<argument index="2" name="weight_scale" type="float" default="1.0">
</argument>
<description>
Adds a new point at the given position with the given identifier. The algorithm prefers points with lower [code]weight_scale[/code] to form a path. The [code]id[/code] must be 0 or larger, and the [code]weight_scale[/code] must be 1 or larger.
Adds a new point at the given position with the given identifier. The [code]id[/code] must be 0 or larger, and the [code]weight_scale[/code] must be 1 or larger.
The [code]weight_scale[/code] is multiplied by the result of [method _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 [code]weight_scale[/code]s to form a path.
[codeblock]
var astar = AStar.new()
astar.add_point(1, Vector3(1, 0, 0), 4) # Adds the point (1, 0, 0) with weight_scale 4 and id 1
@ -315,7 +317,7 @@
<argument index="1" name="weight_scale" type="float">
</argument>
<description>
Sets the [code]weight_scale[/code] for the point with the given [code]id[/code].
Sets the [code]weight_scale[/code] for the point with the given [code]id[/code]. The [code]weight_scale[/code] is multiplied by the result of [method _compute_cost] when determining the overall cost of traveling across a segment from a neighboring point to this point.
</description>
</method>
</methods>

5
doc/classes/AStar2D.xml
View File

@ -43,7 +43,8 @@
<argument index="2" name="weight_scale" type="float" default="1.0">
</argument>
<description>
Adds a new point at the given position with the given identifier. The algorithm prefers points with lower [code]weight_scale[/code] to form a path. The [code]id[/code] must be 0 or larger, and the [code]weight_scale[/code] must be 1 or larger.
Adds a new point at the given position with the given identifier. The [code]id[/code] must be 0 or larger, and the [code]weight_scale[/code] must be 1 or larger.
The [code]weight_scale[/code] is multiplied by the result of [method _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 [code]weight_scale[/code]s to form a path.
[codeblock]
var astar = AStar2D.new()
astar.add_point(1, Vector2(1, 0), 4) # Adds the point (1, 0) with weight_scale 4 and id 1
@ -298,7 +299,7 @@
<argument index="1" name="weight_scale" type="float">
</argument>
<description>
Sets the [code]weight_scale[/code] for the point with the given [code]id[/code].
Sets the [code]weight_scale[/code] for the point with the given [code]id[/code]. The [code]weight_scale[/code] is multiplied by the result of [method _compute_cost] when determining the overall cost of traveling across a segment from a neighboring point to this point.
</description>
</method>
</methods>