dee0e014b1
bugfix: IndexOutOfRangeException in pathfinding due to byte overflow (cherry picked from commit 26fc908ba8fccae04c5f7bee0b9a5784d89ae830)
Pathfinding
This projects includes an a-star pathfinding algorithm, specifically for maps which have a maximum size of 256 x 256. This limitation arises by using byte fields for the coordinates, which saves some memory. There are a few heuristics available but by default the PathFinder uses NoHeuristic which is basically equal to using the Dijkstra algorithm.
Priority Queue
There are two implementations of a priority queue of the Open-List: BinaryMinHeap and IndexedLinkedList. I suggest using the BinaryMinHeap because it's commonly used and it's hard to get IndexedLinkedList working faster under real circumstances. The reason is, that it's pretty hard to get the index fast under all conditions, because the expected open list lengths and estimated costs are always different.
Scoped
The implementation can be used in a scoped way, which means that the pathfinder is only used for a scoped area of the map. This is useful if you want to calculate paths very quickly and you know that the path is only needed in a small area. You can read about that on my blog post: Optimized Pathfinding.
Safezones
Safezones are areas on the map where usually no path should be calculated, except
for special NPCs like guards. By default, the pathfinder will not calculate paths
on the safezone tiles. You can change this behavior by passing the parameter
includeSafezone. The safezones are encoded into the grid cost values as the
highest bit.
Pre-Calculation
In the sub-folder PreCalculation includes a pathfinder which makes use of pre-calculated paths. It's not used yet by OpenMU and needs some further testing.
For more information, visit http://www.gamedev.net/page/resources/_/technical/artificial-intelligence/precalculated-pathfinding-revisited-r1939.
Further optimizations
If we find out that the current implementation is too slow, we could implement Jump Point Search.