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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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21
OpenRA.Game/Map/Map.cs
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@@ -151,6 +151,7 @@ namespace OpenRA
public class Map : IReadOnlyFileSystem
{
public const int SupportedMapFormat = 11;
const short InvalidCachedTerrainIndex = -1;
/// <summary>Defines the order of the fields in map.yaml</summary>
static readonly MapField[] YamlFields =
@@ -448,6 +449,19 @@ namespace OpenRA
}
AllEdgeCells = UpdateEdgeCells();
// Invalidate the entry for a cell if anything could cause the terrain index to change.
Action<CPos> invalidateTerrainIndex = c =>
{
if (cachedTerrainIndexes != null)
cachedTerrainIndexes[c] = InvalidCachedTerrainIndex;
};
// Even though the cache is lazily initialized, we must attach these event handlers on init.
// This ensures our handler to invalidate the cache runs first,
// so other listeners to these same events will get correct data when calling GetTerrainIndex.
CustomTerrain.CellEntryChanged += invalidateTerrainIndex;
Tiles.CellEntryChanged += invalidateTerrainIndex;
}
void UpdateRamp(CPos cell)
@@ -1069,18 +1083,11 @@ namespace OpenRA
public byte GetTerrainIndex(CPos cell)
{
const short InvalidCachedTerrainIndex = -1;
// Lazily initialize a cache for terrain indexes.
if (cachedTerrainIndexes == null)
{
cachedTerrainIndexes = new CellLayer<short>(this);
cachedTerrainIndexes.Clear(InvalidCachedTerrainIndex);
// Invalidate the entry for a cell if anything could cause the terrain index to change.
Action<CPos> invalidateTerrainIndex = c => cachedTerrainIndexes[c] = InvalidCachedTerrainIndex;
CustomTerrain.CellEntryChanged += invalidateTerrainIndex;
Tiles.CellEntryChanged += invalidateTerrainIndex;
}
var uv = cell.ToMPos(this);