For reference I am use Unity as my game engine and the A* Pathfinding Project for path finding as there is no chance I would be able to create anything close to as performant as that in any reasonable amount of time.
So I am looking to build a game that is going to have a very similar style as Prison Architect / Rim World / SimAirport / etc. One of the things that I assume is going to effect performance is path finding. Decisions about the game I have already made that I think relate to this are:
- While I am going to be using Colliders, all of them will be trigger colliders so everything can pass through each other and I will not be use physics for anything else as it has no relevance for my game
- I am going to want to have a soft cap at the map size being 300x300 (90,000 tiles), I might allow bigger sizes but do something like Rim World does in warning the player about possible side effect (whether it be performance or gameplay)
- The map will be somewhat dynamic in that the user will be able to build / gather stuff from the map but outside of that, it should not change very much
Now I am going to build my game around the idea that users would be in control of no more than 50 pawns at any given time (which is something I can probably enforce through the game play) but I am also going to want to have number other pawns that are AI controlled on the map (NPCs, animals, etc.) that would also need path finding enabled. Now I did a basic test in which I have X number of pawns pick a random location in the 300 x 300 map. move towards it, and then change the location every 3-5 seconds. My initial test was pretty slow (not surprising as I was calculating the path every frame for each pawn) so I decided to cache the calculated path results and only update it ever 2 seconds which got me:
100 pawns: 250 - 450 FPS
150 pawns: 160 - 300 FPS
200 pawns: 90 - 150 FPS
250 pawns: 50 - 100 FPS
There is very little extra happening in the game outside of rendering the tilemap.
I would imagine the most pawns on the map at a given time that need path finding might be a 1000 (and I would probably be able to make due with like 500 - 600). Now obviously I would not need all the pawn to be calculation paths every 2 seconds nor would they need to be calculating paths that are so long but even at a 5 second path refresh rate and paths that are up to 10 tiles long, I am still only able to get to about 400 pawns before I start to see some big performance issues. The issue with reducing the refresh rate is that there are going to be cases where maybe a wall is built before the pawns path is refreshed having them walk through the wall but not sure if there is a clean way to update the path only when needed.
I am sure when I don’t run the game in the Unity editor I will see increase performance but I am just trying to figure out what things I could be doing to make sure path finding is as smaller of a performance hit as possible as there is a lot of other simulation stuff I am going to want to run on top of the path finding.