Thing

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Things represent players, monsters, pick-ups, and projectiles. Inside the game, these are known as actors, or mobjs. They also represent obstacles, certain decorations, player start positions and teleport landing sites.

While some mobjs, such as projectiles and special effects, can only be created during play, most things can be placed in a map from a map editor through an associated editor number. When the map is loaded, an actor that corresponds to that number will be spawned at the location of that map thing. See thing types for a listing of all things that have an associated editor number.

THINGS lump[edit]

Doom level format

Level thing data is stored in the THINGS lump. Each entry is 10 bytes long. This format is used by both Doom and Heretic.

Offset Size (bytes) C99 type Description
0 2 int16_t x position
2 2 int16_t y position
4 2 int16_t Angle facing
6 2 int16_t DoomEd thing type
8 2 int16_t Flags

Flags[edit]

bit hex description
0 0x0001 Thing is on skill levels 1 & 2
1 0x0002 Thing is on skill level 3
2 0x0004 Thing is on skill levels 4 & 5
3 0x0008 Thing is waiting in ambush. Commonly known as "deaf" flag.
In fact, it does not render monsters deaf per se.
4 0x0010 Thing is not in single player

Boom flags[edit]

Boom adds the flags:

bit hex description
5 0x0020 Thing is not in deathmatch
6 0x0040 Thing is not in coop

MBF flag[edit]

MBF adds the flag:

bit hex description
7 0x0080 Friendly monster

Hexen Format[edit]

Hexen extended upon the things lump. Hexen things may contain an action special which is executed upon death or pickup of the thing (for monsters and items, respectively). Hexen format also introduced true z-clipping, allowing placement of monsters on the z-axis. Finally, Hexen monsters are also able to have a tag similar to sectors. This is called the thing ID or TID.

Offset Size (bytes) C99 type Description
0 2 int16_t Thing id (tid)
2 2 int16_t X position
4 2 int16_t Y position
6 2 int16_t Starting height
8 2 int16_t Angle facing
10 2 int16_t DoomEd thing type
12 2 int16_t Flags
14 1 uint8_t Hexen action special
15 1 uint8_t Argument 1
16 1 uint8_t Argument 2
17 1 uint8_t Argument 3
18 1 uint8_t Argument 4
19 1 uint8_t Argument 5

Note that Hexen things are 20 bytes in size; 10 bytes larger than things in Doom.

Hexen flags[edit]

bit hex description
0 0x0001 Thing is on skill levels 1 & 2
1 0x0002 Thing is on skill level 3
2 0x0004 Thing is on skill levels 4 & 5
3 0x0008 Thing is waiting in ambush
4 0x0010 Thing is dormant - it will not wake up until it is activated using Thing_Activate
5 0x0020 Thing appears to the Fighter class
6 0x0040 Thing appears to the Cleric class
7 0x0080 Thing appears to the Mage class
8 0x0100 Thing appears in single-player games
9 0x0200 Thing appears in cooperative games
10 0x0400 Thing appears in deathmatch games

Strife Format[edit]

Strife did not alter the thing structure like Hexen did, however it did make use of the unused flag bits.

Strife flags[edit]

bit hex description
0 0x0001 Thing is on skill levels 1 & 2
1 0x0002 Thing is on skill level 3
2 0x0004 Thing is on skill levels 4 & 5
3 0x0008 Thing stands still (only useful for specific enemies)
4 0x0010 Thing will not appear in single player
5 0x0020 Thing is waiting in ambush
6 0x0040 Thing is a friendly monster
7 0x0080 Unused
8 0x0100 Thing is 25% translucent
9 0x0200 Thing is either invisible, or 75% translucent if combined with bit 8.

Doom 64 format[edit]

The Doom 64 THING format is similar to the Doom format except for the inclusion of a z position and an ID. Each entry is 14 bytes long.

Offset Size (bytes) C99 type Description
0 2 int16_t x position
2 2 int16_t y position
4 2 int16_t z position
6 2 int16_t Angle facing
8 2 int16_t DoomEd thing type
10 2 int16_t Flags
12 2 int16_t ID

Doom 64 flags[edit]

Additional flags are defined in comparison to the Doom format, however flags 10 through 12 are not used in any Doom 64 maps.

bit hex description
0 0x0001 Thing is on skill levels 1 & 2
1 0x0002 Thing is on skill level 3
2 0x0004 Thing is on skill level 4
3 0x0008 Thing is waiting in ambush
4 0x0010 Thing is not in single player
5 0x0020 Thing doesn't spawn until triggered in level
6 0x0040 Thing triggers something when picked up
7 0x0080 Thing triggers something when killed
8 0x0100 Thing counts as secret in intermission screen
9 0x0200 Thing ignores other attackers (no infighting)
10 0x0400 Thing doesn't spawn in deathmatch games
11 0x0800 Thing doesn't in standard netgame mode
12 0x1000 Thing appears in nightmare mode (KEX Engine)

Sources[edit]