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Add a hierarchical path finder to improve pathfinding performance.

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Replaces the existing bi-directional search between points used by the pathfinder with a guided hierarchical search. The old search was a standard A* search with a heuristic of advancing in straight line towards the target. This heuristic performs well if a mostly direct path to the target exists, it performs poorly it the path has to navigate around blockages in the terrain. The hierarchical path finder maintains a simplified, abstract graph. When a path search is performed it uses this abstract graph to inform the heuristic. Instead of moving blindly towards the target, it will instead steer around major obstacles, almost as if it had been provided a map which ensures it can move in roughly the right direction. This allows it to explore less of the area overall, improving performance.

When a path needs to steer around terrain on the map, the hierarchical path finder is able to greatly improve on the previous performance. When a path is able to proceed in a straight line, no performance benefit will be seen. If the path needs to steer around actors on the map instead of terrain (e.g. trees, buildings, units) then the same poor pathfinding performance as before will be observed.
This commit is contained in:
RoosterDragon
2022-04-18 20:29:15 +01:00
committed by Matthias Mailänder
parent cea9ceb72e
commit 5a8f91aa21
26 changed files with 1497 additions and 56 deletions
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8
OpenRA.Mods.Common/Pathfinder/DensePathGraph.cs
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@@ -60,7 +60,7 @@ namespace OpenRA.Mods.Common.Pathfinder
/// allowable to be returned in a <see cref="GraphConnection"/>.
/// </summary>
/// <param name="neighbor">The candidate cell. This might not lie within map bounds.</param>
protected virtual bool NeighborAllowable(CPos neighbor)
protected virtual bool IsValidNeighbor(CPos neighbor)
{
return true;
}
@@ -125,7 +125,7 @@ namespace OpenRA.Mods.Common.Pathfinder
{
var dir = directions[i];
var neighbor = position + dir;
if (!NeighborAllowable(neighbor))
if (!IsValidNeighbor(neighbor))
continue;
var pathCost = GetPathCostToNode(position, neighbor, dir);
@@ -142,7 +142,7 @@ namespace OpenRA.Mods.Common.Pathfinder
continue;
var layerPosition = new CPos(position.X, position.Y, cml.Index);
if (!NeighborAllowable(layerPosition))
if (!IsValidNeighbor(layerPosition))
continue;
var entryCost = cml.EntryMovementCost(locomotor.Info, layerPosition);
@@ -155,7 +155,7 @@ namespace OpenRA.Mods.Common.Pathfinder
else
{
var groundPosition = new CPos(position.X, position.Y, 0);
if (NeighborAllowable(groundPosition))
if (IsValidNeighbor(groundPosition))
{
var exitCost = CustomMovementLayers[layer].ExitMovementCost(locomotor.Info, groundPosition);
if (exitCost != PathGraph.MovementCostForUnreachableCell &&