By tracking updates on the ActorMap the HierarchicalPathFinder can be aware of actors moving around the map. We track a subset of immovable actors that always block. These actors can be treated as impassable obstacles just like terrain. When a path needs to be found the abstract path will guide the search around this subset of immovable actors just like it can guide the search around impassable terrain. For path searches that were previously imperformant because some immovable actors created a bottleneck that needed to be routed around, these will now be performant instead. Path searches with bottlenecks created by items such as trees, walls and buildings should see a performance improvement. Bottlenecks created by other units will not benefit.
We now maintain two sets of HPFs. One is aware of immovable actors and will be used for path searches that request BlockedByActor.Immovable, BlockedByActor.Stationary and BlockedByActor.All to guide that around the immovable obstacles. The other is aware of terrain only and will be used for searches that request BlockedByActor.None, or if an ignoreActor is provided. A new UI dropdown when using the `/hpf` command will allow switching between the visuals of the two sets.
When asked to find a path from multiple source locations, the abstract search is used to determine which source locations are viable. Source locations that cannot be reached on the abstract graph are excluded from the local path search. As we know the locations are unreachable, this prevents the local path search from expanding over the entire search space in an attempt to find these unreachable locations, preventing wasted effort.
In order to determine these reachable locations, the abstract search is expanded successively trying to reach each source location each time. However, this failed to account for a property of the ExpandToTarget for which a comment is now added. If the location was found previously, then expanding to try and find it again will fail. If the source locations were close together, it was likely that the initial expansions of the search space would have included them, and thus they would not be found on a later expansion. This would mean these locations would incorrectly be thought unreachable.
To fix this, we check if the location has already been explored (has CellStatus.Closed in the graph). If so we can check the cost to determine if it is reachable.
Activated with the '/path-debug' chat command, this displays the explored search space and costs when searching for paths. It supports custom movement layers, bi-directional searches as well as visualizing searches over the abstract graph of the HierarchicalPathFinder. The most recent search among selected units is shown.
Teach HierarchicalPathFinder to keep a cache of domain indices, refreshing them only on demand and when invalidated by terrain changes. This provides an accurate and quick determination for checking if paths exist between given locations.
By exposing PathExistsForLocomotor on the IPathFinder interface, we can remove the DomainIndex trait entirely.
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.
