LovaP48
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File: Soldier weirdness.hold (2.1 KB)
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In my recently posted hold, A Walk in the Park, I use a soldier horn in one of my rooms to activate a pressure plate in a secluded area Beethro would not be able to reach.
I copied this room over into a new hold, which is attached, I tried to strip it fairly barebones. The two adjacent rooms are empty, I simply wanted to keep the exits and not have "errors".
FYI, I use DROD 5.1.0.6512.

The setup:
I have a horn which is, purely tile-wise, equally apart from two entrances to the east, both being accessible. The aim is to get the soldier to spawn in the southern entrance of these two.
While initially testing, I thought that this is done by some tiebreaking behind the scenes, in which south-eastern direction is somehow preferred to north-eastern.
Seeing KituU's demos, I realized that this does not always happen with the trapdoor & bridge setup that I have in my room.

Labelling the trapdoors with numbers like this (B stands for the bridge between, W for water):

here are the results of all possible dropped trapdoors and the location of the soldier spawn.


Is this intended?
Can anyone point me to a resource about soldier horns, if this was discussed before somewhere?
Or maybe explain exactly HOW do soldier horns work?

Nuntar
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hyperme's "A Detailed Guide to DROD Pathfinding" doesn't mention horns specifically, but since they need to find the closest of multiple targets, they probably have very similar issues to the types discussed. In short: the pathfinding algorithm is impossible for humans to predict because it's inherently chaotic, and making changes to the room that are off the path can change the outcome.

What this means for room design is that if you want a horn to prefer tile A to B, and especially if you want this to be something the player has to achieve deliberately as part of a puzzle, you should try to make sure the player has some way of making the path to A shorter, rather than relying on the algorithm's tiebreaking.

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LovaP48
Level: Master Delver
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Nuntar wrote:
hyperme's "A Detailed Guide to DROD Pathfinding" doesn't mention horns specifically, but since they need to find the closest of multiple targets, they probably have very similar issues to the types discussed. In short: the pathfinding algorithm is impossible for humans to predict because it's inherently chaotic, and making changes to the room that are off the path can change the outcome.

What this means for room design is that if you want a horn to prefer tile A to B, and especially if you want this to be something the player has to achieve deliberately as part of a puzzle, you should try to make sure the player has some way of making the path to A shorter, rather than relying on the algorithm's tiebreaking.

Thanks for the swift reply, Nuntar. I'll take a skim of the linked guide.
Also will try and tweak the room so this is no longer an issue!

hyperme
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Horns shouldn't be subject to pathfinding "chaos", as they use a modified version of brain pathing which doesn't have the flaws that make Stalwart-style pathing unpredictable.

However, there is some weirdness with how room entrances are handled. To determine the "entrance score" for a tile, multiple it's brain score by 100, then add the smaller of the player's X distance or Y distance from that tile. Yeah.

(Having just found out about this I should make an update to the pathing post.)

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hyperme
Level: Smitemaster

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On closer inspection, the bad comparator function that makes Stalwart-style pathing unpredictable is also present in the algorithm that generates brain pathmaps. But since the evaluation order doesn't matter for the final outcome (each tile gets a score), it didn't cause problems.

Except when horns are involved. If two entrances get the same score, they will be subjected to pathfinding "chaos". This because an entrance has to be picked, and there isn't any tiebreaking for equally-scored entrances, so the winner is the one that's earlier in the list of reachable entrances.

Since there are only 44 published rooms with horns according to the search tool, I think fixing this is likely to be safe. Plus a non-zero amount of published rooms have been literally erased due to a bug fix so eradicating some demos isn't that bad.

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[Last edited by hyperme at 01-08-2023 12:27 PM]

mrimer
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Thank you, hyperme!

PR

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