Custom level generation by thicco-catto · Pull Request #750 · TeamREPENTOGON/REPENTOGON

thicco-catto · 2025-11-03T11:51:27Z

Added a new callback and a couple functions that allow for mods to generate custom floors.

MC_PRE_GENERATE_DUNGEON
Called before level::generate_dungeon is called, which places all the rooms in a floor. Passes an RNG.
Return true to cancel vanilla floor generation.

Level:ResetRoomList(bool)
Needs to be called before placing any rooms in the custom level.
The bool is the same as the one in level::init. Testing it so far, setting it to true makes it work all the time.

Level:SetLastBossRoomListIndex(int)
Also needs to be called after creating the custom floor, since not setting it crashes the game when continuing.
Doesn't actually need to be set to a boss room for the game to not crash, but I haven't tested any other side effects apart from boss rooms not spawning the trapdoor if they are not the last.

Sample

local TestMod = RegisterMod("Test Mod", 1)

local function place_at(room, col, row, seed)
    local level = Game():GetLevel()

    local entry = Isaac.LevelGeneratorEntry()
    entry:SetAllowedDoors(15)
    entry:SetColIdx(col)
    entry:SetLineIdx(row)

    level:PlaceRoom(entry, room, seed)
end

local function get_normal_room(seed)
    return RoomConfigHolder.GetRandomRoom(seed, false, StbType.BASEMENT, RoomType.ROOM_DEFAULT, RoomShape.ROOMSHAPE_1x1, -1, -1, 0, 10, 15)
end

TestMod:AddCallback(ModCallbacks.MC_PRE_GENERATE_DUNGEON, function (_, rng)
    local level = Game():GetLevel()
    level:ResetRoomList(true)

    print(rng:GetSeed())

    local start_room = RoomConfigHolder.GetRandomRoom(rng:Next(), false, StbType.SPECIAL_ROOMS, RoomType.ROOM_DEFAULT, RoomShape.ROOMSHAPE_1x1, 2, 2)
    local big_room = RoomConfigHolder.GetRandomRoom(rng:Next(), false, StbType.BASEMENT, RoomType.ROOM_DEFAULT, RoomShape.ROOMSHAPE_2x2, -1, -1, 0, 10, 255)
    local boss_room = RoomConfigHolder.GetRandomRoom(rng:Next(), false, 0, RoomType.ROOM_BOSS, RoomShape.ROOMSHAPE_1x1)

    place_at(start_room, 6, 6, rng:Next())
    place_at(get_normal_room(rng:Next()), 7, 6, rng:Next())
    place_at(boss_room, 8, 6, rng:Next())
    place_at(get_normal_room(rng:Next()), 6, 7, rng:Next())
    place_at(get_normal_room(rng:Next()), 6, 8, rng:Next())
    place_at(get_normal_room(rng:Next()), 7, 8, rng:Next())
    place_at(get_normal_room(rng:Next()), 8, 7, rng:Next())
    place_at(big_room, 8, 8, rng:Next())

    level:SetLastBossRoomListIndex(2)

    return true
end)

EliteMasterEric · 2025-11-04T22:07:20Z

Was going to test this out but it appears to be under heavy development still (I downloaded d313242 and after figuring out the dungeon generator controller, invoking it caused a 0xc0000005 (access violation) error).

Very excited for it to be stable enough to do more stress testing with.

repentogon/Patches/ASMPatches/ASMLevel.cpp

ConnorForan · 2025-11-05T01:43:36Z

repentogon/LuaInterfaces/LuaDungeonGenerator.cpp

+}
+
+LUA_FUNCTION(place_room) {
+	DungeonGenerator* generator = GetDungeonGenerator(L);


I think it would be good for DungeonGenerator itself to contain all its functions such as PlaceRoom (ie, generator->PlaceRoom(config, row, col, seed), and the lua bindings just parse the inputs from lua and redirect to the generator's functions. This will separate the DungeonGenerator logic from the lua bindings, and allow DungeonGenerator code to call its own functions.

Bump. Refactor this logic as DungeonGenerator::PlaceRoom, and just call that from here.

IE, make lua functions minimal (get params from lua, push return values) and do most other things within the DungeonGenerator

repentogon/LuaInterfaces/LuaDungeonGenerator.cpp

ConnorForan · 2025-11-05T01:47:41Z

repentogon/LuaInterfaces/LuaDungeonGenerator.cpp

+#include "Log.h"
+#include "LuaDungeonGenerator.h"
+
+DungeonGenerator* GetDungeonGenerator(lua_State* L) {


LUALIB_API DungeonGenerator* GetDungeonGenerator(lua_State* L)

I don't know exactly how important the LUALIB_API bit is, but its typically used for such functions. Might impact properly surfacing lua errors.

repentogon/LuaInterfaces/LuaDungeonGenerator.h

repentogon/Patches/ASMPatches/ASMLevel.cpp

repentogon/LuaInterfaces/LuaDungeonGenerator.cpp

repentogon/LuaInterfaces/CustomCallbacks.cpp

Guantol-Lemat · 2025-11-07T23:23:27Z

repentogon/LuaInterfaces/LuaDungeonGenerator.cpp

+
+	std::vector<RoomCoords> forbidden_coords = GetForbiddenNeighbors(base_coords, room_shape, doors);
+
+	for (int i = 0; i < this->num_rooms; i++) {


I would suggest having the generator hold a map that ties gridIdx to roomIdx, in order to quickly find the neighboring rooms, and see if a room already occupies this room's slot, as going through the whole room list is not really efficient.

repentogon/LuaInterfaces/LuaDungeonGenerator.cpp

Guantol-Lemat · 2025-11-07T23:34:42Z

repentogon/LuaInterfaces/LuaDungeonGenerator.cpp

+LUA_FUNCTION(Lua_PlaceDefaultStartingRoom) {
+	DungeonGenerator* generator = GetDungeonGenerator(L);
+
+	int doors = (int)luaL_optinteger(L, 2, 15);


Since the start room has essentially a predefined config, and GetRandomRoom can only ever pick one room, due to the variant range being set to just the value 2, there is no need to pass the doors parameter.

The doors parameter limits the allowed doors for the room. It could be useful to mimick the behaviour of the mega satan door/polaroid door

It would be better to use a system similar to the blocked grid indices, rather than having the user having to deal with doors directly. In the original level gen the doors parameter is meant as a way to specify which doors are necessary, not those that are allowed. Of course, we should still allow control over the doors parameter, when doing very specific things, like how secret rooms and ultra secret room generation has to mark certain doors as allowed, post layout generation.

I was basing the doors parameter on the LevelGeneratorEntry.doors parameter, since I'm later setting the LevelGeneratorEntry doors field to that. There it does specify the doors argument refers to the allowed doors.
https://repentogon.com/LevelGeneratorEntry.html

LevelGeneratorEntry is a wrapper for a LevelGenerator_Room and LevelGenerator_Room only specifies the necessary rooms, not the allowed ones. Most likely the parameter was named like that because the necessary rooms end up being used as the allowed rooms when placing the room.

Bump. IDK if I have input here but need to decide how we want to handle non-standard door layouts for the starting room.

Maybe DM guantol.

repentogon/LuaInterfaces/CustomCallbacks.cpp

libzhl/functions/Level.zhl

repentogon/LuaInterfaces/CustomCallbacks.cpp

repentogon/Patches/ASMPatches/ASMLevel.cpp

Guantol-Lemat · 2025-11-10T18:15:59Z

repentogon/LuaInterfaces/LuaDungeonGenerator.cpp

 	this->shape = room->Shape;
 }

+RoomConfig_Room* DungeonGeneratorRoom::GetRoomConfig(uint32_t seed, int required_doors) {


I presume this function was originally meant to do something else due to the unused parameters and unnecessary check for nullptr, what was this supposed to do originally?

bump.

Remove unused parameter, and simply return this->room;

repentogon/LuaInterfaces/CustomCallbacks.cpp

repentogon/LuaInterfaces/LuaDungeonGenerator.cpp

repentogon/LuaInterfaces/CustomCallbacks.cpp

ConnorForan · 2026-03-01T02:47:57Z

repentogon/LuaInterfaces/LuaDungeonGenerator.cpp

 	this->shape = room->Shape;
 }

+RoomConfig_Room* DungeonGeneratorRoom::GetRoomConfig(uint32_t seed, int required_doors) {


bump.

Remove unused parameter, and simply return this->room;

repentogon/LuaInterfaces/LuaDungeonGenerator.cpp

ConnorForan · 2026-03-01T02:52:24Z

repentogon/LuaInterfaces/LuaDungeonGenerator.cpp

+#include "Log.h"
+#include "LuaDungeonGenerator.h"
+
+DungeonGenerator* GetDungeonGenerator(lua_State* L) {


ConnorForan · 2026-03-01T02:53:42Z

repentogon/LuaInterfaces/LuaDungeonGenerator.cpp

+}
+
+LUA_FUNCTION(place_room) {
+	DungeonGenerator* generator = GetDungeonGenerator(L);


Bump. Refactor this logic as DungeonGenerator::PlaceRoom, and just call that from here.

IE, make lua functions minimal (get params from lua, push return values) and do most other things within the DungeonGenerator

ConnorForan · 2026-03-01T02:58:21Z

repentogon/LuaInterfaces/LuaDungeonGenerator.cpp

+
+		return 1;
+	} else {
+		return 0;


I'd prefer this

... luaL_setmetatable(L, lua::metatables::DungeonGeneratorRoomMT); } else { lua_pushnil(L); } return 1;

ConnorForan · 2026-03-01T03:59:13Z

repentogon/resources/scripts/main_ex.lua

+	for callback in GetCallbackIterator(callbackID, param) do
+		local ret = RunCallbackInternal(callbackID, callback, dungeonGenerator, rng, dungeonType)
+
+		if type(ret) == "boolean" and ret then


I think this is very little room for any semblance of mod compatibility for this callback. I believe we've discussed this a bit before.

MC_PRE_GENERATE_DUNGEON is simply not suitable for modifying layouts, only creating them. The use-case being served here is completely custom layouts, and that is not something that mods can collaborate on without explicit compatibility.

With that in mind, I wonder if instead of having a return value at all, we could just do this:

RunCallbackInternal(callbackID, callback, dungeonGenerator, rng, dungeonType) if dungeonGenerator:Validate() then return true else dungeonGenerator:Reset() end

If there was a version of this that was intended to support modifications, it would either be MC_POST_GENERATE_DUNGEON, or a more fleshed out MC_POST_LEVEL_LAYOUT_GENERATED. But that is a weird case. Tacking additional rooms onto the floor is easy enough to do now post-levelgen, so this would come down to practical use-cases for modifying layouts that cannot simply be done later. Stuff to think about/discuss separately, perhaps.

ConnorForan · 2026-03-01T04:36:45Z

repentogon/LuaInterfaces/LuaDungeonGenerator.cpp

+	}
+
+	g_Game->_lastBossRoomListIdx = this->final_boss_index;
+


The DungeonGenerator should support off-grid rooms.

Most likely by adding DungeonGeneratorRoom offGridRooms[21]; (just flip the index)

It should maybe be possible for lua to place RoomConfig_Rooms into these slots (but only by placing RoomConfig_Rooms).

Now, if they were not populated by the mod, we must initialize the following off-grid rooms for (mostly) ALL dungeons:

Error room (-2)

Crawlspace dungeon (-4)

Black market (-6)

Members card secret shop (-13) (except home & ascent)

Stairway to heaven angel shop (-18) (except home)

The Rep+ lil portal room (-20)

The Beast's room in Home?? (-10)

For generate_dungeon specifically we need these as well, regardless of floor with some exceptions (yes, the game always populates boss rush / mega satan / etc):

Boss Rush (-5)

Mega Satan (-7)

Blue Womb trapdoor (-8) (for all stages except blue womb)

Void trapdoor (-9) (for blue womb only)

The "secret exit" room SPECIFICALLY for returning to the main path from Repentance alt path floors (-10)

These will (mostly) boil down to GetRandomRoom calls, but please refer to the 1.7.9b logic (easier to read, tho doesnt help for lil portal) to make sure we do this correctly. Ask for help in the discord thread if needed.

ConnorForan · 2026-03-01T04:40:54Z

repentogon/LuaInterfaces/CustomCallbacks.cpp

+{
+	bool skip = ProcessGenerateDungeonCallback(this, *rng, DEFAULT);
+	if (skip) {
+		return;


I think we need to call generate_mirror_world here, for the appropriate stages. In theory it should just do what it normally does and flips the main layout... Guess we'll find out if it works.

ConnorForan · 2026-03-01T05:04:29Z

repentogon/LuaInterfaces/CustomCallbacks.cpp

+{
+	bool skip = ProcessGenerateDungeonCallback(this, *rng, DEFAULT);
+	if (skip) {
+		return;


We'll need to confirm if there's anything else we need to do here since we're skipping the vanilla code, like anything the game changes or sets that isnt directly tied to the LevelGenerator portion.

I'll need to defer to Guantol for that, though.

thicco-catto and others added 5 commits November 2, 2025 21:23

Reset room list function

8b17521

Added bool parameter

7c047e1

Added callback enum

ea8320c

Merge branch 'TeamREPENTOGON:main' into level-gen

d2bf067

Added RNG parameter to callback

2490b78

epfly6 requested a review from ConnorForan November 3, 2025 11:57

thicco-catto added 4 commits November 4, 2025 18:43

Added dungeon generator controller

8f8c157

Removed test functions and fixed final boss not set

f9fb019

Callback triggers for more dungeon types

f65b5f5

Filter by generation type

d313242

ConnorForan requested a review from Guantol-Lemat November 5, 2025 00:24

ConnorForan reviewed Nov 5, 2025

View reviewed changes

thicco-catto added 15 commits November 5, 2025 18:30

Moved custom callback to appropiate file

e2f77b4

Fixed return values for lua functions

32e508d

Renamed lua functions

1feba7f

PlaceRoom returns the room

bfab985

Generator returns bool

845072c

Dungeon generator has own RNG

c2cc975

Refactored floor generation

47dbdd9

Moved implementations to source file

7d5ce08

Added room shape check and swapped col/row

57a718d

Added door validation

05c839a

Added shape field to DungeonGeneratorRoom

9a7e37e

Added PlaceDefaultStartingRoom

40605fd

Fixed constructors

797a52d

Added dungeon type param to callback

8ad7897

Changed some pointers to references

2e6f9f4

Guantol-Lemat reviewed Nov 7, 2025

View reviewed changes

Changed resetLilPortalRoom param

e1b7d98

thicco-catto added 8 commits November 8, 2025 11:08

Removed unnecesary include

bd2415e

Use bitset to check room placement

52c50b5

Created utils file and generation type enum

c308a3e

Enum is passed as number to callback

0bbb155

DungeonGenerator now holds index for final boss

d89ff98

Removed some debug logs

fc5098b

Refactored DungeonGenerator to use LevelGenerator

6edd184

Removed ununsed fields

2c37191

Guantol-Lemat reviewed Nov 10, 2025

View reviewed changes

ConnorForan reviewed Nov 11, 2025

View reviewed changes

thicco-catto added 3 commits November 11, 2025 17:04

Added BlockIndex function

86ff2bb

Changed optional return

062d157

Added custom callback logic

4732779

ConnorForan reviewed Mar 1, 2026

View reviewed changes


		std::vector<RoomCoords> forbidden_coords = GetForbiddenNeighbors(base_coords, room_shape, doors);

		for (int i = 0; i < this->num_rooms; i++) {

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thicco-catto commented Nov 3, 2025

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Guantol-Lemat Nov 8, 2025 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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Guantol-Lemat Nov 8, 2025 •

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