Water: Spawning, Pathfinding and Ladder Building

Continuing the discussion from New villager spawns in an inaccessible area:

This is an extension of the linked bug report. Hostile mobs and livestock also spawn in inaccessible places. I know hostile mobs have been reported before as well, but water is pretty universally not well considered in terms of AI logic.

Water-Related Problems:

  1. Non-aquatic hostile mobs spawn there.
  2. Livestock (Shepherd spawns) spawn there.
  3. Loot and log blocks drop there.
  4. Ladders placed from shore down into water stop when they hit water, and pathfinding logic takes a very long time to return and finish the job.
  5. Pathfinding through water takes a very long time.

Bonus Bug!
Did you know Entlings can climb ladders? Is that intentional?

Steps to Reproduce:
For #2 above: Place a ladder leading down into the water. Promote someone to shepherd. Define all three livestock zones nearby. Observe shepherd constantly going up and down the water ladder to retrieve spawned livestock (and get attacked by Water Wolves and Water Entlings).

For #4 above: Spawn a hearthling underwater. Spawn a class talisman and place it in a stockpile. Spawn another hearthling on land. Spawn some wood for a ladder. Request a ladder to be placed that allows the underwater hearthling to reach the stockpile. Wait for the ladder to be placed the first time (note it may only place one block of ladder down to the water line). Attempt to promote the underwater hearthling. It cannot path to the talisman because the ladder is incomplete. Wait to see if the pathfinder ever figures out the ladder needs to be finished. If it does, the promotion will succeed and the hearthling will escape the water.

For #5 above: Same test as above but this time use a peninsula and mine a standard 4-block mineshaft width from one side to the other. Now place ladders on both sides and spawn a hearthling on the far side of the water and attempt to promote her. Note: This problem may only be a symptom of #4, because when I experienced it, I did not yet realize the ladders were only partially deployed, and it may have resolved itself once the hearthling could path down one and up the other properly.

On a related note re #5, underwater items, marked looted or not, often take much longer for the AI to retrieve.

Alpha 14, Dev 2818 x64

Save Game:
One is Day 4, the other Day 9, so you can observe the progression in case it’s helpful

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