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.

ConnorForan · 2025-11-05T01:47:41Z

+#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.

Guantol-Lemat · 2025-11-07T23:23:27Z

+
+	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.

Guantol-Lemat · 2025-11-07T23:34:42Z

+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.

Guantol-Lemat · 2025-11-10T18:15:59Z

 	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;

ConnorForan · 2026-03-01T02:47:57Z

 	this->shape = room->Shape;
 }

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


bump.

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

ConnorForan · 2026-03-01T02:52:24Z

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


ConnorForan · 2026-03-01T04:36:45Z

+	}
+
+	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.

Added support for all of these except for the last one "The "secret exit" room SPECIFICALLY for returning to the main path from Repentance alt path floors (-10)", I couldn't really see when this room spawns exactly (or at all). Could you specify further?

ConnorForan · 2026-03-01T05:04:29Z

+{
+	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.

Sync branch

Guantol-Lemat · 2026-05-28T15:25:11Z

+
+	bool CanRoomBePlaced(XY& base_coords, int shape, int allowed_doors, bool allow_unconnected);
+
+	void BlockPositionsFromAllowedDoords(XY& base_coords, int shape, int allowed_doors);


Typo.
Also this is unused.

Guantol-Lemat · 2026-05-28T15:26:37Z

+
+#pragma region Helpers
+
+void PushCoordsIfValid(std::vector<XY>& list, XY& coords) {


This method should be static, as it is not exposed in the LevelGenUtils API

Guantol-Lemat · 2026-05-28T15:27:20Z

All methods here should be in their a "LevelGenUtils" namespace.

Guantol-Lemat · 2026-05-28T15:30:31Z

+}
+
+std::vector<XY> GetOccupiedCoords(XY& base_coords, int shape) {
+	std::vector<XY> occupied_coords = {};


Minor optimization: since we know the max amount of occupied coords, we can safely reserve enough space for the vector and avoid reallocations.

Guantol-Lemat · 2026-05-28T15:32:29Z

+}
+
+std::vector<XY> GetForbiddenNeighbors(XY& base_coords, int shape, int doors) {
+	std::vector<XY> forbidden_neighbors = {};


You can preallocate enough memory for this vector as well.

Guantol-Lemat · 2026-05-28T21:26:20Z

+	bool has_final_room = this->final_boss_index >= 0;
+
+	// Check if all rooms can fetch a room config
+	int initial_seed = this->rng->_seed;


It might be better to just create a copy of the RNG, that way it's guaranteed there are no side effects.

Guantol-Lemat · 2026-05-28T21:48:41Z

+	}
+
+	int maxVariant = (int)luaL_optinteger(L, 8, -1);
+	if (maxVariant < minVariant && maxVariant >= 0) {


Not really a problem with this implementation, since this is a copy of the GetRandomRoom checks, but using int instead of unsigned int complicates the logic a bit. -1 is used as a way to quickly reach the maximum unsigned integer, making it "uncapped", rather than being a special value.

Guantol-Lemat · 2026-05-28T21:49:47Z

+	this->ResetLevelGenerator();
+
+	this->final_boss_index = -1;
+	for (size_t i = 0; i < 169; i++)


Nitpick: Given that rooms need to be synchronized with the LevelGenerator rooms I would place this reset in ResetLevelGenerator.

Guantol-Lemat · 2026-05-28T21:50:05Z

+	this->level_generator._rooms.clear();
+}
+
+void DungeonGenerator::Reset() {


Offgrid rooms are not reset.

Guantol-Lemat · 2026-05-28T22:16:13Z

+	DungeonGeneratorRoom rooms[169];
+	DungeonGeneratorRoom off_grid_rooms[20];
+	RNG* rng;
+	Level* level;


Is this necessary?

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

Comment thread repentogon/LuaInterfaces/CustomCallbacks.cpp Outdated

Comment thread repentogon/LuaInterfaces/LuaDungeonGenerator.cpp

Comment thread repentogon/LuaInterfaces/LuaDungeonGenerator.cpp Outdated

Comment thread repentogon/LuaInterfaces/LuaDungeonGenerator.cpp Outdated

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

thicco-catto and others added 12 commits May 25, 2026 19:11

Merge branch 'level-gen' into main

070fb5b

Merge pull request #2 from thicco-catto/main

f685113

Sync branch

Clean up and added PlaceRandomRoom

8ab1113

Callback doesn't require return value

7dcae5d

Off grid rooms get initialized

3d8c9ab

Lua methods to place off grid rooms

4b7b38c

Added LUALIB_API to helper func

a42a1e0

Lil portal room resets according to vanilla logic

f425662

Fixed off grid rooms for blue womb

9027c2f

Generate downpour and mines dungeons

9194c9e

Removed test log

68ae5e0

Reset flags and donationModGreed

f8b2626

Guantol-Lemat reviewed May 28, 2026

View reviewed changes


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

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


		bool CanRoomBePlaced(XY& base_coords, int shape, int allowed_doors, bool allow_unconnected);

		void BlockPositionsFromAllowedDoords(XY& base_coords, int shape, int allowed_doors);


		#pragma region Helpers

		void PushCoordsIfValid(std::vector<XY>& list, XY& coords) {

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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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