Thing

In Doom, things are used to represent players, monsters, pick-ups, and projectiles. Inside the game, these are known as actors. There are three ways to get an actor into your map. Most things are actors, so the names are often used interchangeably. A few things, however, are not actors, such as player start points.

Referencing things

DoomEd numbers are the numbers used in the editor to represent an actor. When the map is loaded, an actor that corresponds to that number will be spawned at the location of that map thing. Although many actors have DoomEd numbers, not all of them do. For instance, a blue key card has a DoomEd number, but a rocket flying through the air does not.

Spawn numbers are the numbers used by specials such as Thing_Spawn to spawn actors in the game once the user has started playing the map. Although DoomEd numbers and spawn numbers both describe actors, they are not interchangeable—you must not use a spawn number on a map thing, and you must not use a DoomEd number for instance as a Thing_Spawn parameter.

Actor Names are the actual names each actor has internally (to test these you may want to try out the summon console command). These are used with the functions SpawnSpot and Spawn which allow you to spawn any actor available with Thing_Spawn and also all other actors (though some actors aren't meant to be spawned) such as cameras, scenery or whatever you might require.

If you create a new actor with the DECORATE lump, you can specify both the spawn number (SpawnID), and the DoomEd number (DoomEdNum). The name you give the new DECORATE item is also its actor name, so you can also spawn it using that.

There is also a third set of numbers used to represent actors that is only important for DeHackEd and similar. These numbers correspond to the order the actors were defined in the vanilla exe. They have no meaning outside of ZDoom's DeHackEd loader and as a result are not a property. In Strife, they were used to identify actor classes in conversations, but ZDoom turned these into the ConversationID property because identical actors had different numbers in the different versions of Strife available.

Specification (Doom format)

Bytes	Data type	Description	Notes
0-1	Signed short	X position
2-3	Signed short	Y position
4-5	Unsigned short	Angle	0=East, 45=NE, 90=North 135=NW, 180=West, 225=SW, 270=South
6-7	Unsigned short	Type	See the list of standard editor numbers
8-9	Unsigned Short	Spawn flags

Specification (Hexen format)

Bytes	Data type	Description	Notes
0-1	Unsigned short	Thing ID	This value is used for scripts and specials
2-3	Signed short	X position
4-5	Signed short	Y position
6-7	Signed short	Z position
8-9	Unsigned short	Angle	0=East, 45=NE, 90=North 135=NW, 180=West, 225=SW, 270=South
10-11	Unsigned short	Type	See the list of standard editor numbers
12-13	Unsigned short	Spawn flags
14	Unsigned byte	Action special	An action to be executed when this thing is destroyed or picked up
15	Unsigned byte	Action argument 1
16	Unsigned byte	Action argument 2
17	Unsigned byte	Action argument 3
18	Unsigned byte	Action argument 4
19	Unsigned byte	Action argument 5

Spawn flags

There are several conflicts in the flag list, depending on game. Map translators are used to define how values are associated to flags in a binary map. UDMF allows to solve these conflicts by not using a bitfield array but instead referring to each flag by name. Several flags are only available in this map format.

Flag	Z-Bit	Z-Hex	D-Bit	D-Hex	S-Bit	S-Hex	Description	UDMF name
EASY	0	0x0001	0	0x0001	0	0x0001	Thing is spawned on skills #1 and #2	skill1 + skill2
MEDIUM	1	0x0002	1	0x0002	1	0x0002	Thing is spawned on skill #3	skill3
EASY	2	0x0004	2	0x0004	2	0x0004	Thing is spawned on skills #4 and #5	skill4 + skill5
AMBUSH	3	0x0008	3	0x0008	5	0x0020	Thing is lying in ambush (AMBUSH flag is set)	ambush
DORMANT	4	0x0010					Thing is DORMANT until activated	dormant
FIGHTER	5	0x0020					Thing is spawned when player class #1 is present	class1
CLERIC	6	0x0040					Thing is spawned when player class #2 is present	class2
MAGE	7	0x0080					Thing is spawned when player class #3 is present	class3
SINGLE	8	0x0100					Thing appears in single-player games	single
COOPERATIVE	9	0x0200					Thing appears in cooperative games	dm
DEATHMATCH	10	0x0400					Thing appears in deathmatch games	coop
SHADOW	11	0x0800			8	0x0100	Thing is 25% translucent	translucent
SHADOW	12	0x1000			9	0x0200	Thing is invisible	invisible
FRIENDLY	13	0x2000			6	0x0040	FRIENDLY monster using Strife logic	strifeally
STANDSTILL	14	0x4000			3	0x0008	Thing stands still (only useful for specific Strife monsters or friendlies)	standing
SECRET							Thing is a secret pickup	countsecret
NOTSINGLE			4	0x0010	4	0x0010	Thing does not appear in single player
NOTDEATHMATCH			5	0x0020			Thing does not appear in single deathmatch
NOTCOOPERATIVE			6	0x0040			Thing does not appear in cooperative
FRIEND			6	0x0040			Thing is a friendly monster using MBF logic (remapped to FRIENDLY)	friend
BADEDITORCHECK			8	0x0100			Thing was placed in a map editor that sets undefined flags
							Thing is spawned on skill #1	skill1
							Thing is spawned on skill #2	skill2
							Thing is spawned on skill #4	skill4
							Thing is spawned on skill #5	skill5
							Thing is spawned on skill #6	skill6
							Thing is spawned on skill #7	skill7
							Thing is spawned on skill #8	skill8
							Thing is spawned on skill #9	skill9
							Thing is spawned on skill #10	skill10
							Thing is spawned on skill #11	skill11
							Thing is spawned on skill #12	skill12
							Thing is spawned on skill #13	skill13
							Thing is spawned on skill #14	skill14
							Thing is spawned on skill #15	skill15
							Thing is spawned on skill #16	skill16
							Thing is spawned when player class #4 is present	class4
							Thing is spawned when player class #5 is present	class5
							Thing is spawned when player class #6 is present	class6
							Thing is spawned when player class #7 is present	class7
							Thing is spawned when player class #8 is present	class8
							Thing is spawned when player class #9 is present	class9
							Thing is spawned when player class #10 is present	class10
							Thing is spawned when player class #11 is present	class11
							Thing is spawned when player class #12 is present	class12
							Thing is spawned when player class #13 is present	class13
							Thing is spawned when player class #14 is present	class14
							Thing is spawned when player class #15 is present	class15
							Thing is spawned when player class #16 is present	class16

UDMF properties

In addition to the UDMF-exclusive spawn flags above, the following properties can only be used on a thing in UDMF mode:

• Conversation = <int>: assigns a conversation ID to the thing. This corresponds to the id property of a conversation, allowing for dialogue trees specific to a given thing rather than to an entire actor class.
• arg0str = <name>: gives a string value to the first argument. This is used for named scripts and Hexen breakable items.
• arg1str = <name>: gives a string value to the second argument. This is used by certain Thing spawning specials.