A random map generator for Doom engine games
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What is ObHack?

ObHack is my name for some modifications Fritz and myself have made to Oblige, a random map generator for the original Doom, Doom 2, and Heretic. It is name thusly because it is a hacked Oblige, and as a tribute to the ObHacks posted to the once-great Usenet newsgroup alt.hackers.

ObHack can make random maps for Doom, Doom2, TNT, Plutonia, FreeDoom (Phase II), Heretic, and Blasphemer.

ObHack is a fork of version 2 of Oblige (Oblige 0.81-0.97).


ObHack has the following features that Oblige2 does not have:

  • Real secret areas that take work to find
  • Improved random number generator which allows arbitrary English or Spanish text to be the seed, resulting in a nearly infinite number of possible seeds
  • New modes: Single Player + Deathmatch, Deathmatch without exits, and Capture the Flag
  • Progressive level size: Levels get bigger as one gets to higher levels in the wad
  • Enclosures and variable room sizes
  • Adjustable light level
  • Tiny and gigantic level sizes
  • Option to have swarms or even more monsters
  • Monster traps are back (removed in Oblige 0.94)
  • Boss levels now have boss monsters in them
  • Choice of player starting weapon
  • More texture packs, including contributions from Mr. Chris
  • Deathmatch starts in single player maps
  • And other features not listed here

Oblige URL: http://oblige.sourceforge.net/

Using ObHack

To use ObHack in Windows, copy over the ObHack.exe binary from Win32-binary/ to the directory ObHack-engine-00#.# (replace “#” with numbers), and then run the ObHack binary from that directory. To use ObHack in other operating systems, compile ObHack (see below for instructions) and then run the built binary.

ObHack settings

  • Random seed: This determines the random numbers used to generate the .wad file. Using the same settings and seed will generate the same levels again. Note that, unlike Oblige, the seed is a string, not a number.
  • New seed: Change the seed, replacing it by a four digit number.
  • Game: The game to generate wad files for.
  • Length: How many levels to put in the randomly generated megawad. Note that, as of ObHack 008.3, generating an episode or full game results in there being boss arenas in the final episode levels (E#M8 or MAP30).
  • Port: This was originally planned to allow a level to have, say, Boom extensions, but was never implemented (later versions of Oblige did end up implementing this)
  • Mode: Single player makes a monster fight. Co-op makes a harder monster fight, but one can have multiple players fight the monsters together. Deathmatch makes maps without monsters and a different layout designed for players to fight each other. “SP and DM” makes single player maps which can also be used for deathmatch matches. “DM (no exit)” removes the exit from the no-monster deathmatch maps; these are for ports which allow the level to change after a certain number of frags or time. “CTF”, as of ObHack 008.2, generates random Capture the Flag maps for Doom ports with CTF support; note that the CTF maps are not symmetric.
  • Level size: How big the levels are. “Progressive” makes the maps in a megawad bigger as one goes through the levels, resetting the size to small at the beginning of an episode. “Expansive” is similar, but keeps making the levels bigger until making the boss arena.
  • Prog/Exp. Max Level Size: If using the “Progressive” or “Expansive” level sizes, this caps how big the levels will become. Otherwise, this element is greyed out.
  • Quest length: This adjusts how many rooms one has to go through in a single player (not deathmatch) map before getting a prize (key, weapon, item, etc.)
  • Monsters: How many monsters the level has. Only used for single player maps.
  • Players: How many player starts to have in a deathmatch map.
  • Puzzles: How many keys or switches one has to find before being able to open a door and continue the map. Only used in single player maps.
  • Weapons: How many weapons to place in a deathmatch map.
  • Outdoors: How common outdoors areas are
  • Stairs: This determines if the map generator randomly places a lift or stair when going up or down in the map. If set to “lifts + stairs”, the map generator decides; if set to “Mostly stairs”, the generator will only place a lift if it can not fit a stairway.
  • Enclosures: Whether to have monster traps in Doom single player maps. If the game type is “Heretic” or “Blasphemer”, this is greyed out.
  • Room size: How big to make each room on the map.
  • Rm lighting: How dark or bright to make the rooms.
  • Steepness: How much up and down the levels should have.
  • Hallways: How common hallways between rooms are.
  • Health: How much health to give the player.
  • Ammo: How much ammo for weapons to give the player.
  • Switches: In single player maps with puzzles, whether we have only key puzzles, switch puzzles, or a mixture of the two.
  • Key type: In Doom levels, what kind of keys can a level have.
  • Start weapon: This lets a player start with a weapon at the beginning of a level.
  • Secrets: How common secret areas are in single player maps.

Batch mode

ObHack can make maps in batch mode, where a megawad can be generated without interacting with the GUI. This allows .bat files or *NIX shell scripts to generate a large number of .wad files.

To do this:

  • Open up the GUI and slect the settings one wishes to have when generating batch levels.
  • Close the GUI, which will save these settings in the file CONFIG.cfg
  • From the command line, invoke ObHack with a single argument: A seed number, which is also the filename ObHack will write when invoked in batch mode. The seed needs to start with a number, but can have non-numeric characters in it (such as ending with .wad)
  • ObHack will open up the GUI, generate the map, then terminate when the map is made.
  • When generating a level in batch mode, in addition to outputting the logs in to the file LOGS.txt, ObHack outputs them to the standard output.
  • In batch mode, the generated levels will be in the same directory as the ObHack binary.

One can use a *NIX shell script (Windows users can use Cygwin, MSYS, UWIN, or other *NIX-in-Windows environments to run this script) to generate a large number of levels automatically. This script also writes CONFIG.cfg to determine the settings in the megawad:


cat > CONFIG.cfg << EOF
-- Settings --
seed = 5464
game = freedoom
port = nolimit
mode = sp
length = full

-- Adjustments --
size = small
maxsize = huge
steep = little
puzzles = more
mons = normal
health = more
ammo = more
outdoors = more
iweapon = hardcore2
switches = keys
keytype = both
roomsize = normal
lighting = bright
enclosure = true
questlength = normal
hallways = normal
stairs = stairs
secrets = common

while [ $A -lt 10000 ] ; do
	./ObHack $A-FreeDoom.wad
	A=$( expr $A + 1 )

Compiling ObHack

These are the files needed to make the Win32 binary of ObHack. To compile, you will need to install both MinGW-3.4.2 and MSYS-1.0.10. Once you do that, do something like this:

export FLAGS=-Os
export CFLAGS=-Os
cd fltk-1.1.9
cd ..
cd zlib-1.2.3
cd ..
cd glbsp-2.24-source
# You may have to edit the makefile
cd ..
cd ObHack-engine-*
cd gui
# You may have to edit the Makefile

MinGW and MSYS install directions are here:


Note that MinGW-3.4.2 doesn’t work in Windows 10; try using a newer version of MinGW (no, I will not help you here), Windows 7, or a non-networked Windows XP machine to compile ObHack.

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