Sector

A sector is an area referenced by sidedefs on the linedefs, with variable height determined by its floor and ceiling values. Sectors should be closed areas, meaning that all the sidedefs that reference a particular sector should make up a closed shape. Unclosed sectors can be used for a few special effects, but under some circumstances they can lead to undesirable results (including crashes).

A sector does not have to be a single polygon. For instance, two squares can be separate and non-contiguous, but still be part of the same sector.

A sector entry specifies the following:

Ceiling flat - Name of the flat (texture) used on the ceiling of the sector.

Floor flat - Name of the flat used on the floor.

Ceiling height - Height of the ceiling.

Floor height - Height of the floor.

Lighting - How bright the sector is.

Sector tag - A number that makes the sector a target of the action specified by any linedef with the same tag number. Used, for example, to alter the sector's ceiling and/or floor height, lighting level or flats.

Sector type - Special properties of the sector. This is used to give the sector a damaging floor (for things like lava and slime), have the sector's light level change constantly, enable wind or currents or even push the player in a certain direction. See below.

Sector structure

Doom level format
Things Linedefs Sidedefs Vertices Segs Subsectors Nodes Sectors Reject Blockmap
Extensions: Behavior FraggleScript ACS GL nodes Macros Leafs

Each sector is 26 bytes large. Sectors are stored in WAD files in the following format:

Offset	Size (bytes)	C99 type	Description
0	2	int16_t	Floor height
2	2	int16_t	Ceiling height
4	8	int8_t[8]	Name of floor texture
12	8	int8_t[8]	Name of ceiling texture
20	2	int16_t	Light level
22	2	int16_t	Special Type
24	2	int16_t	Tag number

At level load time, several additional variables are generated for each sector and stored in the internal sector data structure. These include:

linecount - the total number of linedefs associated with the sector.

lines - a list of every linedef associated with the sector.

blockbox - the coordinates defining a rectangular bounding box enclosing the sector, with the bounding box enlarged so that the edges line up with the blockmap.

soundorg - the coordinates for any sound emitted by the sector; automatically set to the center of a precise bounding box surrounding the sector.

PlayStation format

The Sony PlayStation port of Doom uses the following sector format, with 28 bytes per record:

Offset	Size (bytes)	C99 type	Description
0	2	int16_t	Floor height
2	2	int16_t	Ceiling height
4	8	int8_t[8]	Name of floor texture
12	8	int8_t[8]	Name of ceiling texture
20	1	uint8_t	Light level
21	1	uint8_t	Color ID
22	2	int16_t	Special Type
24	2	int16_t	Tag number
26	2	int16_t	Flags

Final Doom for PlayStation format

The PlayStation port of Final Doom uses the following sector format, with 16 bytes per record:

Offset	Size (bytes)	C99 type	Description
0	2	int16_t	Floor height
2	2	int16_t	Ceiling height
4	2	int16_t	Index of floor texture
6	2	int16_t	Index of ceiling texture
8	1	uint8_t	Light level
9	1	uint8_t	Color ID
10	2	int16_t	Special Type
12	2	int16_t	Tag number
14	2	int16_t	Flags

Doom 64 format

The Doom 64 sector format differs from the Doom format in multiple places: textures are represented by indexes into a hash table of texture names, the light level is replaced by five color values, and a flags field is added. Thus each sector is 24 bytes long.

Offset	Size (bytes)	C99 type	Description
0	2	int16_t	Floor height
2	2	int16_t	Ceiling height
4	2	int16_t	Index of floor texture
6	2	int16_t	Index of ceiling texture
8	10	int16_t[5]	Color indexes (floor, ceiling, thing, wall top, wall bottom)
18	2	int16_t	Special Type
20	2	int16_t	Tag number
22	2	int16_t	Flags

Sector types

The type field of the sector structure is used to specify lighting, damage, and a few other special effects.

• There are linedef types that can change the sector type field during gameplay, either to zero or to a copy of another sector's type field. This is how, for example, a safe bridge rises out of a pool of nukage.
• Damage is halved at skill level 1.
• Damage is split between health and armor (if any).
• All light-related sector types alternate between the initial light value of the sector, and the initial light value of the adjacent sector with the lowest light value. The effect of the sector's lighting being altered by a linedef varies depending on both the linedef type and sector type used. Changing the adjacent sector's light value does not change the lighting effect.

Doom

In Doom, the sector type values are mutually exclusive.

Type	Class	Effect
0		Normal
1	Light	Blink random
2	Light	Blink 0.5 second
3	Light	Blink 1.0 second
4	Both	20% damage per second plus light blink 0.5 second
5	Damage	10% damage per second
7	Damage	5% damage per second
8	Light	Oscillates
9	Secret	Player entering this sector gets credit for finding a secret
10	Door	30 seconds after level start, ceiling closes like a door
11	End	20% damage per second. The level ends when the player's health drops below 11% and is touching the floor. Player health cannot drop below 1% while anywhere in a sector with this sector type. God mode cheat (iddqd), if player has activated it, is nullified when player touches the floor for the first time.
12	Light	Blink 1.0 second, synchronized
13	Light	Blink 0.5 second, synchronized
14	Door	300 seconds after level start, ceiling opens like a door
16	Damage	20% damage per second
17	Light	Flickers randomly

Boom

Boom (and compatible source ports) support the Doom sector types above, and also provide "generalized" sector types. The latter are based on bit fields, which allows several sector type properties to be independently specified for a sector. Texture change linedef types can be used to switch some or all of these properties dynamically, outside lighting.

Bits 0 through 4 specify the lighting type in the sector, and the same codes that Doom uses are employed (0, 1, 2, 3, 4, 8, 12, 13 and 17 from above).

Flag	Bits	Effect
32	5	5% damage per second
64	6	10% damage per second
96	5+6	20% damage per second
128	7	Secret sector
256	8	Enable friction effects
512	9	Enable pusher/puller effects

Heretic

Heretic uses a greater variety of sector types, notably to control its own friction and wind effects. Like in Doom, the values are mutually exclusive.

Type	Class	Effect
0		Normal
1	Light	Blink random
2	Light	Blink 0.5 second
3	Light	Blink 1.0 second
4	Combo	5% lava damage per second plus scroll east 28 and light blink 0.5 second
5	Damage	5% lava damage per second
7	Damage	4% sludge damage per second
8	Light	Oscillates
9	Secret	Player entering this sector gets credit for finding a secret
10	Door	30 seconds after level start, ceiling closes like a door
11	No-op	Does nothing
12	Light	Blink 0.5 second, synchronized
13	Light	Blink 1.0 second, synchronized
14	Door	300 seconds after level start, ceiling opens like a door
15	Friction	Low friction
16	Damage	8% lava damage per second
20	Scroller	Scroll east 5
21	Scroller	Scroll east 10
22	Scroller	Scroll east 25
23	Scroller	Scroll east 30
24	Scroller	Scroll east 35
25	Scroller	Scroll north 5
26	Scroller	Scroll north 10
27	Scroller	Scroll north 25
28	Scroller	Scroll north 30
29	Scroller	Scroll north 35
30	Scroller	Scroll south 5
31	Scroller	Scroll south 10
32	Scroller	Scroll south 25
33	Scroller	Scroll south 30
34	Scroller	Scroll south 35
35	Scroller	Scroll west 5
36	Scroller	Scroll west 10
37	Scroller	Scroll west 25
38	Scroller	Scroll west 30
39	Scroller	Scroll west 35
40	Wind	Push east 5
41	Wind	Push east 10
42	Wind	Push east 25
43	Wind	Push north 5
44	Wind	Push north 10
45	Wind	Push north 25
46	Wind	Push south 5
47	Wind	Push south 10
48	Wind	Push south 25
49	Wind	Push west 5
50	Wind	Push west 10
51	Wind	Push west 25

Hexen

Like Heretic, Hexen uses a large number of mutually-exclusive sector types.

Type	Class	Effect
0		Normal
1	Light	Phased light (use lightlevel between 0 and 63 for the starting phase)
2	Light	Phased light sequence start (use types 3 and 4 in neighboring sectors)
3	Light	Light sequence step (to be used alternatively with type 4 for a light sequence)
4	Light	Light sequence step (to be used alternatively with type 3 for a light sequence)
9	Secret (Unused)	Player entering this sector gets credit for finding a secret — however this is nonfunctional and pointless since Hexen does not have an intermission screen.
26	Stairs	Mark sector to be used for building normal stairs
27	Stairs	Mark sector to be used for building synchronized stairs
40	Wind	Push east 5
41	Wind	Push east 10
42	Wind	Push east 25
43	Wind	Push north 5
44	Wind	Push north 10
45	Wind	Push north 25
46	Wind	Push south 5
47	Wind	Push south 10
48	Wind	Push south 25
49	Wind	Push west 5
50	Wind	Push west 10
51	Wind	Push west 25
198	Lightning	Light level increases by up to 64 units during a lightning flash
199	Lightning	Light level increases by up to 32 units during a lightning flash
200	Sky	Use the secondary sky texture if the level does not use a double sky
201	Scroller	Scroll north 5
202	Scroller	Scroll north 10
203	Scroller	Scroll north 25
204	Scroller	Scroll east 5
205	Scroller	Scroll east 10
206	Scroller	Scroll east 25
207	Scroller	Scroll south 5
208	Scroller	Scroll south 10
209	Scroller	Scroll south 25
210	Scroller	Scroll west 5
211	Scroller	Scroll west 10
212	Scroller	Scroll west 25
213	Scroller	Scroll northwest 5
214	Scroller	Scroll northwest 10
215	Scroller	Scroll northwest 25
216	Scroller	Scroll northeast 5
217	Scroller	Scroll northeast 10
218	Scroller	Scroll northeast 25
219	Scroller	Scroll southeast 5
220	Scroller	Scroll southeast 10
221	Scroller	Scroll southeast 25
222	Scroller	Scroll southwest 5
223	Scroller	Scroll southwest 10
224	Scroller	Scroll southwest 25

Strife

In Strife, the sector type values are also mutually exclusive.

Type	Class	Effect
0		Normal
1	Light	Blink random
2	Light	Blink 0.5 second
3	Light	Blink 1.0 second
4	Both	5% damage every 32 tics plus light blink 0.5 second
5	Damage	+2 increase to nukagecount
7	Damage	5% damage every 32 tics
8	Light	Oscillates
9	Secret	Player entering this sector gets credit for finding a secret
10	Door	30 seconds after level start, ceiling closes like a door
11	End	20% damage per second. When player dies, level ends
12	Light	Blink 0.5 second, synchronized
13	Light	Blink 1.0 second, synchronized
14	Door	300 seconds after level start, ceiling opens like a door
15	Damage	Instant death: 999% damage every tic
16	Damage	+4 to nukagecount
17	Light	Flickers randomly
18	Scroller	Water current, angle and strength depend on sector tag value

ZDoom

ZDoom and compatible source ports provide a superset of all sector types based on the Hexen types, including both mutually-exclusive types and generalized flags. The following table is used for maps in the Hexen map format or in UDMF with the ZDoom namespace.

Type	Class	Effect
0		Normal
1	Light	Phased light (use lightlevel between 0 and 63 for the starting phase)
2	Light	Phased light sequence start (use types 3 and 4 in neighboring sectors)
3	Light	Light sequence step (to be used alternatively with type 4 for a light sequence)
4	Light	Light sequence step (to be used alternatively with type 3 for a light sequence)
26	Stairs	Mark sector to be used for building normal stairs
27	Stairs	Mark sector to be used for building synchronized stairs
40	Wind	Push east 5
41	Wind	Push east 10
42	Wind	Push east 25
43	Wind	Push north 5
44	Wind	Push north 10
45	Wind	Push north 25
46	Wind	Push south 5
47	Wind	Push south 10
48	Wind	Push south 25
49	Wind	Push west 5
50	Wind	Push west 10
51	Wind	Push west 25
65	Light	Blink random
66	Light	Blink 0.5 second
67	Light	Blink 1.0 second
68	Both	20% damage per second plus light blink 0.5 second
69	Damage	10% damage per second
71	Damage	5% damage per second
72	Light	Oscillates
74	Door	30 seconds after level start, ceiling closes like a door
75	End	20% damage per second. When player dies, level ends
76	Light	Blink 0.5 second, synchronized
77	Light	Blink 1.0 second, synchronized
78	Door	300 seconds after level start, ceiling opens like a door
79	Friction	Low friction
80	Damage	20% damage per second
81	Light	Flickers randomly
82	Damage	5% lava damage per second
83	Damage	8% lava damage per second
84	Combo	5% lava damage per second plus scroll east and light blink 0.5 second
85	Damage	4% sludge damage per second
87	Fog	Sector uses outside fog even if the ceiling texture is not the sky texture
105	Damage	+2 increase to nukagecount
115	Damage	Instant death: 999% damage every tic
116	Damage	+4 to nukagecount
118	Scroller	Water current, angle and strength depend on sector tag value
195	Automap	Hidden: sector texture is not shown on the textured automap
196	Healing	Restores 1 hit point every 32 tics
197	Lightning	Light level increases as much as outdoor sectors do during a lightning flash
198	Lightning	Light level increases by up to 64 units during a lightning flash
199	Lightning	Light level increases by up to 32 units during a lightning flash
200	Sky	Use the secondary sky texture if the level does not use a double sky
201	Scroller	Scroll north 5
202	Scroller	Scroll north 10
203	Scroller	Scroll north 25
204	Scroller	Scroll east 5
205	Scroller	Scroll east 10
206	Scroller	Scroll east 25
207	Scroller	Scroll south 5
208	Scroller	Scroll south 10
209	Scroller	Scroll south 25
210	Scroller	Scroll west 5
211	Scroller	Scroll west 10
212	Scroller	Scroll west 25
213	Scroller	Scroll northwest 5
214	Scroller	Scroll northwest 10
215	Scroller	Scroll northwest 25
216	Scroller	Scroll northeast 5
217	Scroller	Scroll northeast 10
218	Scroller	Scroll northeast 25
219	Scroller	Scroll southeast 5
220	Scroller	Scroll southeast 10
221	Scroller	Scroll southeast 25
222	Scroller	Scroll southwest 5
223	Scroller	Scroll southwest 10
224	Scroller	Scroll southwest 25
225	Scroller	Scroll east 5
226	Scroller	Scroll east 10
227	Scroller	Scroll east 25
228	Scroller	Scroll east 30
229	Scroller	Scroll east 35
230	Scroller	Scroll north 5
231	Scroller	Scroll north 10
232	Scroller	Scroll north 25
233	Scroller	Scroll north 30
234	Scroller	Scroll north 35
235	Scroller	Scroll south 5
236	Scroller	Scroll south 10
237	Scroller	Scroll south 25
238	Scroller	Scroll south 30
239	Scroller	Scroll south 35
240	Scroller	Scroll west 5
241	Scroller	Scroll west 10
242	Scroller	Scroll west 25
243	Scroller	Scroll west 30
244	Scroller	Scroll west 35
Flag	Bits	Effect
0x0100	8	5% damage per second
0x0200	9	10% damage per second
0x0300	8+9	20% damage per second
0x0400	10	Secret sector
0x0800	11	Enable friction effects
0x1000	12	Enable pusher/puller effects

Doom 64

In Doom 64, the sector type values are mutually exclusive like before, but mainly pertain to lighting behavior.

Type	Class	Effect
0		Normal
1	Light	Random flickering light
2	Light	Blink light 0.5 seconds
3	Light	Blink light 1.0 seconds
8	Light	Normal pulsing light
9	Light	Slow pulsing light
11	Light	Random pulsing light
12	Light	Same as type 3
13	Light	Same as type 2
17	Light	Fire light flickering
202	Light	Constant blink light slow
204	Light	Blink light rapid
205	Light	Start of sequenced light sectors
206	Light	Blink light very rapid
208	Light	Constant blink light fast
666	Damage	Instant kill thing when being crushed

The extra flags field controls further sector characteristics that were defined as sector types in the original Doom.

Flag	Bit	Description
0x0001	0	Reverb sounds (echo) played in sector
0x0002	1	Reverb sounds (echo) played in sector and multiply factor by 2
0x0004	2	Water effect (floors only)
0x0008	3	All flagged sectors with same special type will sync all light flickers/strobe across all sectors
0x0010	4	Scrolling floors/ceilings will scroll at twice the speed
0x0020	5	Count as secret on intermission screen when entering this sector
0x0040	6	Damage player x5
0x0080	7	Damage player x10
0x0100	8	Damage player x20
0x0200	9	Hide sector in automap (textured mode)
0x0400	10	Enable ceiling scrolling
0x0800	11	Enable floor scrolling
0x1000	12	Scroll texture west
0x2000	13	Scroll texture east
0x4000	14	Scroll texture north
0x8000	15	Scroll texture south

Sources

• Unofficial Doom Specs
• Boom source code: boomref.txt
• Doom 64 Tech Bible at Doomworld/idgames