Often no passable path on unknown map with 2 players

[Langbart]

A problem was noticed by rollieoo on a certain map, both opponents cannot reach each other.

• Forum: ​Two halves map (21/Jan/22)

to reproduce

• Set up a game
  • Player: 2
  • Maptype: Random
  • Map: Unknown
  • Landscape: Passes
• try to get your units across the mountain, often this won't work

example:

~/0ad/binaries/system/pyrogenesis -conf=mod.enabledmods:"mod public" -quickstart -autostart="random/unknown" -autostart-seed=1563851758  -autostart-size=256 -autostart-player=-1

bisect

• It was not possible for me to find the changeset number.
• In a quick test in A24b, the mountain was overcomeable, but if you try a few times, the problem could also occur there.
• The problem also occurs in A23b.

solution (1)

A simple solution would be to adjust the map creation for 2 players || numPlayers == 2 so that there is always a lake in between.

​Line 656 in Unknown.js

Line
656	if (randBool(2/5) *|| numPlayers == 2*)
657	{
658	g_Map.log("Create central lake");
659	createArea(
660	new ClumpPlacer(diskArea(fractionToTiles(0.1)), 0.7, 0.1, Infinity, mapCenter),
661	[
662	new SmoothElevationPainter(ELEVATION_SET, waterHeight, 3),
663	new TileClassPainter(clWater)
664	]);
665	}

input from elexis (1) (22/Jan/22)

[08:52:57] Langbart Hello, do you think the solution is good enough for https://trac.wildfiregames.com/ticket/6422 ?
[...]
[10:34:17] elexis making a lake is certainly a possibility but it changes the map gameplay a lot
[...]
[10:44:32] elexis so I guess either the placer isnt returning an area or the painter isnt doing something to it
[10:45:24] elexis same with the "Fill area between the paths" part, also Im not sure why that one paints clWater there when there isnt any water, probably to have nothing else placed there, but thats often asking for bugs like fish on land
[10:45:57] elexis better would be to add a specific class clPassage and have all the remaining statements make sure not to place on clPassage (water and land alike), but (probably) unrelated
[...]
[10:49:12] elexis could also be that the passage is too small on the given mapsize or something
[10:49:27] elexis yeah that looks like it
[...]
[10:55:53] elexis but its probably a wrong parameter in the mapscript rather than a rmgen library bug, judging by the screenshot

solution (2)

Replace diskArea(fractionToTiles(0.05)) with 0. ​Line 666 in Unknown.js

Line
666	else
667	{
668	g_Map.log("Fill area between the paths");
669	createArea(
670	new ClumpPlacer(*0*, 0.7, 0.1, Infinity, mapCenter),
671	[
672	new SmoothElevationPainter(ELEVATION_SET, heightMountain, 4),
673	new TileClassPainter(clWater)
674	]);
675	}

input from elexis (2) (22/Jan/22)

[13:18:07] elexis so the problem is first it places the passage through the middle then it places the mountain in the middle blocking the passage
[...]
[13:19:23] elexis then the bug was probably introduced in the first version of the map

solution (3) by elexis

[13:25:51] elexis you add an if (n != 2)
[13:26:22] // Dont block the passage we just created if the passage goes through the center

[Langbart]

add a new solution and input from elexis

[Langbart]

issue was found, the map should not create a passage and then block it on numPlayers == 2

[Langbart]

added patch number

[Stan]

In 26578:

Fix unknown map: opponent being unreachable
Patch by: @elexis
Tweaks by: @Langbart, @marder
Fixes: #6422
Differential Revision: ​https://code.wildfiregames.com/D4457