MBF

MBF (Marine's Best Friend) is a source port created by Lee Killough after he left the Boom team. It is regarded by some as Boom's successor. As with Boom, MBF was limited to running under MS-DOS.

MBF adds several features:


 * Friendly monsters, including single-player helper dogs.
 * Bug fixes, such as a fix for the blockmap limit (MBF includes an internal blockmap builder).
 * A "beta" mode, in which MBF simulates the behaviour of press release beta version of Doom. This includes the version of the BFG9000 included in the beta.
 * Higher-resolution 640x400 screen mode.
 * A means to change the level's sky texture (Linedef action 271).
 * Several new Dehacked thing flags (TOUCHY, BOUNCES, FRIEND) and action functions with parameters (e.g. Spawn, PlaySound, RandomJump).

MBF was originally licensed under the non-free Doom Source License, but Killough has since relicensed his work under the GNU GPL.

MBF formed the basis of the SMMU port by Simon Howard. In 2004 it was ported to Windows with the name WinMBF by Team Eternity.

Bugs
Due to changes in the collision detection algorithms, a respawned or resurrected monster can sometimes become "glued" to another monster or to a wall. This bug propagated into later ports which used the MBF source, such as PrBoom.

Locked doors requiring all three colors of keys, available through generalized linedef types (a feature inherited from Boom), will not open if the player is carrying a yellow skull key no matter how many of the other keys they have. However, they will open if you have both a blue key and a red key, regardless of type, even if you have no yellow key whatsoever. Thus, levels that use these doors can be completed earlier than intended or impossible to finish depending on how the keys are arranged and what key types are used.

In the released binary, the partial invisibility effect is not rendered correctly due to a minor mistake made during addition of support for the 640x400 screen resolution. There is no noise to the effect like normal; instead objects appear to be translucent gray masses. Lee Killough later released a patch to the source code which fixed this problem, but declined to provide a new binary distribution.

MBF 2.04 Update
In 2014, an unofficial updated version of MBF versioned as MBF 2.04, was released on the VOGONS forums by Gerwin Broers (Gerwin). After this release, Gerwin started using intermediate updates under the 2.04 moniker. 19 updates have been released since, which added the following features:


 * Plays demos from the classic v1.2 version of Doom, using code from PrBoom.
 * At least 10% better performance compared to MBF v2.03.
 * Tolerant to running within Windows NT/2000/XP.
 * Use the super shotgun in Doom 1, with parameter "-ssg -file ssg.wad", combined with "-unlock" in case of shareware.
 * Parameters "-stdvid" and "-bestvid" for benchmarking under comparable game settings.
 * FPS counter option (run a timedemo to unlock the 35 FPS framerate cap).
 * Authentic FM music.
 * Improved sound driver setup, with Doom theme.
 * Added WSS, GUS PnP, ESS and Soundscape drivers. Improved Sound Blaster 2.0/Pro and MPU-401 driver.
 * Reliable video initialization and access, independent from Allegro.
 * Startup console similar to classic Doom.
 * Imported many bugfixes from different sources.

The last release of MBF 2.04 was version 19, released September 10, 2017. It formed the basis for several spinoff builds, which are listed below.

MBF386
MBF386 is a separate build of the latest MBF 2.04 source release targetting Intel 386 processors by its original author, Gerwin Broers. Merely referenced in a note in the same VOGONS thread, Gerwin uploaded a separate build to his home directory, without specific source code, on September 23, 2017.

MBF-Sigil/MBF-SNM
In 2019, developer Sakitoshi created his own build of the then latest MBF 2.04 source release, entitled MBF-Sigil. The first release was on June 8, 2019. Alongside all of MBF 2.04's features, Sakitoshi initially only sought to add SIGIL support, taken from the Libretro PrBoom source tree to achieve playability of SIGIL under DOS. Later, support for No Rest for the Living and Master Levels for Doom II was added and the build was rebranded to MBF-SNM. The latest release under this moniker, named SNM10, was released on December 2, 2019.