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 the UpdateCellBlocking encountered a transit-only cell (the bibs around a building) it would bail from the loop. This would leave the cellCrushablePlayers set to all players. It would update the cell cache and mark that cell as a crushable location.
When CanMoveFreelyInto would later evaluate a cell, it would consider it passable because the crushable check would pass (cellCache.Crushable.Overlaps(actor.Owner.PlayerMask)) rather than because the transit check (otherActor.OccupiesSpace is Building building && building.TransitOnlyCells().Contains(cell)) would pass.
Although this meant the cell was treated as passable in either scenario, it means the cache contained incorrect data. The cell does not contain any crushable actors but the cache would indicate it did. Correcting this means we can rely on the crushability information stored in the cache to be accurate.
Since bbf5970bc1 we update frozen actors only when required.
In 8339c6843e a regression was fixed where actors created in line of sight would be invisible.
Here, we fix a related regression where cloaked units that are revealed, and then frozen when you move out of line of sight would lack tooltips.
The fix centers around the setting of the Hidden flag. In the old code this used CanBeViewedByPlayer which checks for visibility modifiers and then uses the default visibility. The bug with this code is that when a visibility modifier was not hiding the actor, then we would report the default visibility state instead. However the frozen visibility state applies here which means if the frozen actor is visible, then we consider the actor to be hidden and therefore tooltips will not appear. In the fixed version we only consider the modifiers. This means a visibility modifier such as Cloak can hide the frozen actor tooltips. But otherwise we do not consider the frozen actor to be hidden. This prevents a frozen actor from hiding its own tooltips in some unintended circular logic. Hidden now becomes just a flag to indicate if the visibility modifiers are overriding things, as intended.
Since bbf5970bc1 we only update frozen actor state on demand rather than every tick. However when the actor was initially created we were failing to set the initial visibility state if the frozen actor was invisible.
With this fix, we now set the visibility states on creation correctly. This fixes an issue where enemy actors created within line of sight would not appear.
During the refactoring to introduce HierarchicalPathFinder, custom costs were no longer applied to source locations. The logic being that if we are already in the source location, then there should be no cost added to it to get there - we are already there!
Path searches support the ability to go from multiple sources to a single target, but the reverse is not supported. Some callers that require a search from a single source to one of multiple targets perform their search in reverse, swapping the source and targets so they can run the search, then reversing the path they are given so things are the correct way around again. For callers that also use a custom cost like the harvester code that do this in order to find free refineries, they might want the custom cost to be applied to the source location. The harvester code uses this to filter out overloaded refineries. It wants to search from a harvester to multiple refineries, and thus reverses this in order to perform the path search. Without the custom cost being applied to the "source" locations, this filtering logic never gets applied.
To fix this, we now apply the custom cost to source locations. If the custom cost provides an invalid path, then the source location is excluded entirely. Although this seems unintuitive on its own, this allows searches done "in reverse" to work again.
Previously, actors that were visible would refresh their frozen actor state every tick in preparation for the actor becoming hidden, and the frozen actor appearing as a placeholder instead.
By using ICreatesFrozenActors.OnVisibilityChanged when can avoid refreshing the state constantly, and instead just refresh it the moment the frozen actor needs to appear. This provides a nice performance improvement on the cost on managing frozen actors.
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.
To prepare them for documentation generation.
Also added descriptions to SpriteSequence implementations and their properties.
Also made a few code style fixes.
Prior to ef44c31a72eab61a597cf539ee4b138e94b254fe, Locomotor would be earlier in the trait initialization sequence than SpawnStartingUnits. After this commit, the initialization sequence was perturbed and SpawnStartingUnits would initialize first. When SpawnStartingUnits would query CanEnterCell this would generate a null reference as Locomotor had not yet initialized.
SpawnStartingUnitsInfo is made to initialize NotBefore LocomotorInfo to enforce the required trait ordering.
The restores the previous behaviour before FindUnitPathToTargetCell was introduced. This prevents callers such as the harvester code crashing when a harvester tries to route home to a refinery, but there are no refineries.
Prior to ef44c31a72eab61a597cf539ee4b138e94b254fe, Locomotor would be earlier in the trait initialization sequence than SpawnMapActors. Locomotor would assume no actors on the map, and register to update blocked cells when new ones were added. When SpawnMapActors created actors, Locomotor was made aware and kept up-to-date.
After this commit, the initialization sequence was perturbed and SpawnMapActors would initialize first. Locomotor would assume no actors on the map and thus be unaware of these starting units, meaning those starting units would not cause blocking, allowing units to pass through them.
There are two possible fixes. SpawnMapActorsInfo can initialize NotBefore<LocomotorInfo>, enforcing that actors are spawned after locomotor is ready. Or we can remove the assumption in Locomotor that the map starts empty, and have it update blocked cells on startup. The latter seems cleaner, so any other traits that may want to spawn actors don't have to be aware sequencing their initialization with the Locomotor trait, instead things would "just work".
Some path searches, using PathSearch, were created directly at the callsite rather than using the pathfinder trait. This means some searches did not not benefit from the performance checks done in the pathfinder trait. It also means the pathfinder trait was not responsible for all pathing done in the game. Fix this with the following changes:
- Create a sensible shape for the IPathFinder interface and promote it to a trait interface, allowing theoretical replacements of the implementation. Ensure none of the concrete classes in OpenRA.Mods.Common.Pathfinder are exposed in the interface to ensure this is possible.
- Update the PathFinder class to implement the interface, and update several callsites manually running pathfinding code to instead call the IPathFinder interface.
- Overall, this allows any implementation of the IPathFinder interface to intercept and control all path searching performed by the game. Previously some searches would not have used it, and no alternate implementations were possible as the existing implementation was hardcoded into the interface shape.
Additionally:
- Move the responsibility of finding paths on completed path searches from pathfinder to path search, which is a more sensible location.
- Clean up the pathfinder pre-search optimizations.
Requires<T> means that trait of type T will be initialized first, and asserts that at least one exists. The new NotBefore<T> means that trait of type T will be initialized first, but allows no traits.
This allows traits to control initialization order for optional dependencies. They want to be initialized second so they can rely on the dependencies having been initialized. But if the dependencies are optional then to not throw if none are present.
We apply this to Locomotor which was previously using AddFrameEndTask to work around trait order initialization. This improves the user experience as the initialization is applied whilst the loading screen is still visible, rather than the game starting and creating jank by performing initialization on the first tick.
