Mobj

A mobj, short for map object, is a type of thinker that roughly corresponds to things: players, monsters, items, obstacles and decorations, map spots such as teleport destinations or boss shooter destinations, and so on, are all map objects. Mobjs are also frequently called actors. Code comments present them as such:

//  MapObj data. Map Objects or mobjs are actors, entities,
//  thinker, take-your-pick... anything that moves, acts, or
//  suffers state changes of more or less violent nature.

In the source code, mobjs are represented by the mobjtype_t enum and the mobj_t and mobjinfo_t structures. The order in which the mobj types are declared in the info.h and info.c files corresponds to their DeHackEd number, and most DeHackEd changes consist in altering the values of the mobjinfos' properties. The mobjinfo corresponds to the "class" of a mobj (for example, imp) whereas the mobj corresponds to a particular "instance" of the class (for example, the imp that waits in the exit room of E1M1). The mobjinfo_t structure determines how many hit points a mobj starts with, which states it uses, what its flags are, what sounds it makes, what is its reaction time, its movement speed, and so on. The mobj_t structure stores its current position and momentum, which sector it is in, what is its current state, its current target, where it should respawn in Nightmare! mode, and so on.

Flags

Doom games

The original Doom source code defined the following mobj flags (as enum mobjflag_t in file p_mobj.h).

Symbolic constant	Bit(s)	Value (decimal)	Value (hex)	Source code comment
MF_SPECIAL	0	1	0x1	Call P_SpecialThing() when touched.
MF_SOLID	1	2	0x2	Blocks.
MF_SHOOTABLE	2	4	0x4	Can be hit.
MF_NOSECTOR	3	8	0x8	Don't use the sector links (invisible but touchable).
MF_NOBLOCKMAP	4	16	0x10	Don't use the blocklinks (inert but displayable)
MF_AMBUSH	5	32	0x20	Not to be activated by sound, deaf monster.
MF_JUSTHIT	6	64	0x40	Will try to attack right back.
MF_JUSTATTACKED	7	128	0x80	Will take at least one step before attacking.
MF_SPAWNCEILING	8	256	0x100	On level spawning (initial position), hang from ceiling instead of stand on floor.
MF_NOGRAVITY	9	512	0x200	Don't apply gravity (every tic), that is, object will float, keeping current height or changing it actively.
MF_DROPOFF	10	1024	0x400	This allows jumps from high places.
MF_PICKUP	11	2048	0x800	For players, will pick up items.
MF_NOCLIP	12	4096	0x1000	Player cheat. ???
MF_SLIDE	13	8192	0x2000	Player: keep info about sliding along walls.
MF_FLOAT	14	16384	0x4000	Allow moves to any height, no gravity. For active floaters, e.g. cacodemons, pain elementals.
MF_TELEPORT	15	32768	0x8000	Don't cross lines or ??? look at heights on teleport.
MF_MISSILE	16	65536	0x10000	Don't hit same species, explode on block. Player missiles as well as fireballs of various kinds.
MF_DROPPED	17	131072	0x20000	Dropped by a demon, not level spawned. E.g. ammo clips dropped by dying former humans.
MF_SHADOW	18	262144	0x40000	Use fuzzy draw (shadow demons or spectres), temporary player invisibility powerup.
MF_NOBLOOD	19	524288	0x80000	Flag: don't bleed when shot (use puff), barrels and shootable furniture shall not bleed.
MF_CORPSE	20	1048576	0x100000	Don't stop moving halfway off a step, that is, have dead bodies slide down all the way.
MF_INFLOAT	21	2097152	0x200000	Floating to a height for a move, ??? don't auto float to target's height.
MF_COUNTKILL	22	4194304	0x400000	On kill, count this enemy object towards intermission kill total. Happy gathering.
MF_COUNTITEM	23	8388608	0x800000	On picking up, count this item object towards intermission item total.
MF_SKULLFLY	24	16777216	0x1000000	Special handling: skull in flight. Neither a cacodemon nor a missile.
MF_NOTDMATCH	25	33554432	0x2000000	Don't spawn this object in death match mode (e.g. key cards).
MF_TRANSLATION	26, 27	201326592	0xC000000	Player sprites in multiplayer modes are modified using an internal color lookup table for re-indexing. If 0x4 0x8 or 0xc, use a translation table for player colormaps
MF_TRANSSHIFT	1, 3, 4	26	0x1A	Hmm ???.

Heretic

In the Heretic source code, the flags are defined in the doomdef.h file. All flags from Doom are retained. An additional, second set of flags was also added. These flags are shown in the table below.

Symbolic constant	Bit(s)	Value (decimal)	Value (hex)	Source code comment
MF2_LOGRAV	0	1	0x00000001	alternative gravity setting
MF2_WINDTHRUST	1	2	0x00000002	gets pushed around by the wind specials
MF2_FLOORBOUNCE	2	4	0x00000004	bounces off the floor
MF2_THRUGHOST	3	8	0x00000008	missile will pass through ghosts
MF2_FLY	4	16	0x00000010	fly mode is active
MF2_FOOTCLIP	5	32	0x00000020	if feet are allowed to be clipped
MF2_SPAWNFLOAT	6	64	0x00000040	spawn random float z
MF2_NOTELEPORT	7	128	0x00000080	does not teleport
MF2_RIP	8	256	0x00000100	missile rips through solid targets
MF2_PUSHABLE	9	512	0x00000200	can be pushed by other moving mobjs
MF2_SLIDE	10	1024	0x00000400	slides against walls
MF2_ONMOBJ	11	2048	0x00000800	mobj is resting on top of another mobj
MF2_PASSMOBJ	12	4096	0x00001000	Enable z block checking. If on, this flag will allow the mobj to pass over/under other mobjs.
MF2_CANNOTPUSH	13	8192	0x00002000	cannot push other pushable mobjs
MF2_FEETARECLIPPED	14	16384	0x00004000	a mobj's feet are now being cut
MF2_BOSS	15	32768	0x00008000	mobj is a major boss
MF2_FIREDAMAGE	16	65536	0x00010000	does fire damage
MF2_NODMGTHRUST	17	131072	0x00020000	does not thrust target when damaging
MF2_TELESTOMP	18	262144	0x00040000	mobj can stomp another
MF2_FLOATBOB	19	524288	0x00080000	use float bobbing z movement
MF2_DONTDRAW	20	1048576	0x00100000	don't generate a vissprite

Hexen

In the Hexen source code, the flags are defined in the h2def.h file. All Doom and Heretic flags are retained, but some have been changed or replaced. New flags have also been added. The table below shows only the changed and new flags.

Symbolic constant	Bit(s)	Value (decimal)	Value (hex)	Source code comment	Status
MF_ALTSHADOW	17	131072	0x20000	alternate fuzzy draw	Replaces MF_DROPPED
MF_ICECORPSE	23	8388608	0x800000	a frozen corpse (for blasting)	Replaces MF_COUNTITEM
MF_TRANSLATION	26, 27, 28	469762048	0x00000000	use a translation table (>>MF_TRANSHIFT)	Redefined
MF2_BLASTED	3	8	0x00000008	missile will pass through ghosts	Replaces MF2_THRUGHOST
MF2_FLOORCLIP	5	32	0x00000020	if feet are allowed to be clipped	Replaces MF2_FOOTCLIP
MF2_DROPPED	14	16384	0x00004000	dropped by a demon	Replaces MF2_FEETARECLIPPED
MF2_IMPACT	21	2097152	0x00200000	an MF_MISSILE mobj can activate SPAC_IMPACT	New
MF2_PUSHWALL	22	4194304	0x00400000	mobj can push walls	New
MF2_MCROSS	23	8388608	0x00800000	can activate monster cross lines	New
MF2_PCROSS	24	16777216	0x01000000	can activate projectile cross lines	New
MF2_CANTLEAVEFLOORPIC	25	33554432	0x02000000	stay within a certain floor type	New
MF2_NONSHOOTABLE	26	67108864	0x04000000	mobj is totally non-shootable, but still considered solid	New
MF2_INVULNERABLE	27	134217728	0x08000000	mobj is invulnerable	New
MF2_DORMANT	28	268435456	0x10000000	thing is dormant	New
MF2_ICEDAMAGE	29	536870912	0x20000000	does ice damage	New
MF2_SEEKERMISSILE	30	1073741824	0x40000000	is a seeker (for reflection)	New
MF2_REFLECTIVE	31	2147483648	0x80000000	reflects missiles	New

External links

• File p_mobj.h from the original Doom source code release