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Fix reversed path searches from inaccessible locations.

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The Harvester trait and MoveAdjacentTo activity called the pathfinder but had a single source and multiple targets. The pathfinder interface only allows for the opposite: multiple sources and a single target. To work around this they would swap the inputs. This works in most cases but not all cases. One aspect of asymmetry is that an actor may move out of an inaccessible source cell, but not onto an inaccessible target cell.

Searches that involved an inaccessible source cell and that applied this swapping method would therefore fail to return a path, when a valid path was possible. Although a rare case, once good way to reproduce is to use a production building that spawns actors on inaccessible cells around it, such as the RA naval yard. A move order uses the pathfinder correctly and the unit will move out. Using a force attack causes the unit to use the broken "swapped" mechanism in MoveAdjacentTo and it will be stuck.

This asymmetry has been longstanding but the pathfinding infrastructure only sporadically accounted for it. It is now documented and applied consistently. Create a new overload on the pathfinder trait that allows a single source and multiple targets, so callers have an overload that does what they need and won't be tempted to swap the positions and run into this issue.

Internally, this requires us to teach Locomotor to ignore the self actor when performing movement cost checks for these "in reverse" searches so the unit doesn't consider the cell blocked by itself.
This commit is contained in:
RoosterDragon
2023-03-27 18:32:51 +01:00
committed by Paul Chote
parent e4ba9733fe
commit 4ec5a4b34a
11 changed files with 171 additions and 38 deletions
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20
OpenRA.Mods.Common/Traits/World/Locomotor.cs
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@@ -204,30 +204,30 @@ namespace OpenRA.Mods.Common.Traits
return terrainInfos[index].Speed;
}
public short MovementCostToEnterCell(Actor actor, CPos destNode, BlockedByActor check, Actor ignoreActor, SubCell subCell = SubCell.FullCell)
public short MovementCostToEnterCell(Actor actor, CPos destNode, BlockedByActor check, Actor ignoreActor, bool ignoreSelf = false, SubCell subCell = SubCell.FullCell)
{
var cellCost = MovementCostForCell(destNode);
if (cellCost == PathGraph.MovementCostForUnreachableCell ||
!CanMoveFreelyInto(actor, destNode, subCell, check, ignoreActor))
!CanMoveFreelyInto(actor, destNode, subCell, check, ignoreActor, ignoreSelf))
return PathGraph.MovementCostForUnreachableCell;
return cellCost;
}
public short MovementCostToEnterCell(Actor actor, CPos srcNode, CPos destNode, BlockedByActor check, Actor ignoreActor)
public short MovementCostToEnterCell(Actor actor, CPos srcNode, CPos destNode, BlockedByActor check, Actor ignoreActor, bool ignoreSelf = false)
{
var cellCost = MovementCostForCell(destNode, srcNode);
if (cellCost == PathGraph.MovementCostForUnreachableCell ||
!CanMoveFreelyInto(actor, destNode, SubCell.FullCell, check, ignoreActor))
!CanMoveFreelyInto(actor, destNode, SubCell.FullCell, check, ignoreActor, ignoreSelf))
return PathGraph.MovementCostForUnreachableCell;
return cellCost;
}
// Determines whether the actor is blocked by other Actors
bool CanMoveFreelyInto(Actor actor, CPos cell, SubCell subCell, BlockedByActor check, Actor ignoreActor)
bool CanMoveFreelyInto(Actor actor, CPos cell, SubCell subCell, BlockedByActor check, Actor ignoreActor, bool ignoreSelf)
{
// If the check allows: We are not blocked by other actors.
if (check == BlockedByActor.None)
@@ -260,7 +260,7 @@ namespace OpenRA.Mods.Common.Traits
// Cache doesn't account for ignored actors, subcells, temporary blockers or transit only actors.
// These must use the slow path.
if (ignoreActor == null && subCell == SubCell.FullCell &&
if (ignoreActor == null && !ignoreSelf && subCell == SubCell.FullCell &&
!cellFlag.HasCellFlag(CellFlag.HasTemporaryBlocker) && !cellFlag.HasCellFlag(CellFlag.HasTransitOnlyActor))
{
// We already know there are uncrushable actors in the cell so we are always blocked.
@@ -282,7 +282,7 @@ namespace OpenRA.Mods.Common.Traits
var otherActors = subCell == SubCell.FullCell ? world.ActorMap.GetActorsAt(cell) : world.ActorMap.GetActorsAt(cell, subCell);
foreach (var otherActor in otherActors)
if (IsBlockedBy(actor, otherActor, ignoreActor, cell, check, cellFlag))
if (IsBlockedBy(actor, otherActor, ignoreActor, ignoreSelf, cell, check, cellFlag))
return false;
return true;
@@ -303,7 +303,7 @@ namespace OpenRA.Mods.Common.Traits
if (check > BlockedByActor.None)
{
bool CheckTransient(Actor otherActor) => IsBlockedBy(self, otherActor, ignoreActor, cell, check, GetCache(cell).CellFlag);
bool CheckTransient(Actor otherActor) => IsBlockedBy(self, otherActor, ignoreActor, false, cell, check, GetCache(cell).CellFlag);
if (!sharesCell)
return world.ActorMap.AnyActorsAt(cell, SubCell.FullCell, CheckTransient) ? SubCell.Invalid : SubCell.FullCell;
@@ -320,9 +320,9 @@ namespace OpenRA.Mods.Common.Traits
/// <remarks>This logic is replicated in <see cref="HierarchicalPathFinder.ActorIsBlocking"/> and
/// <see cref="HierarchicalPathFinder.ActorCellIsBlocking"/>. If this method is updated please update those as
/// well.</remarks>
bool IsBlockedBy(Actor actor, Actor otherActor, Actor ignoreActor, CPos cell, BlockedByActor check, CellFlag cellFlag)
bool IsBlockedBy(Actor actor, Actor otherActor, Actor ignoreActor, bool ignoreSelf, CPos cell, BlockedByActor check, CellFlag cellFlag)
{
if (otherActor == ignoreActor)
if (otherActor == ignoreActor || (ignoreSelf && otherActor == actor))
return false;
var otherMobile = otherActor.OccupiesSpace as Mobile;