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The THING Resource

by Matthew S. Fell [with revisions by Steve Benner] / Ben Morris

 

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 THING structure

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THINGS are player start positions, monsters, weapons, keys, barrels, etc. The size of each THINGS lump in a DOOM WAD will be a multiple of ten, since each THING requires ten bytes to describe it. Hexen's THINGS are twice this size, having an extra ten bytes. This structure determines how the THING is created at the inception of the level, and also exerts some control over how it behaves during play.

The structure of the THING in DOOM and Hexen
Offset (DOOM)	Offset (Hexen)	Size	Purpose
-	0	short	THING ID: used in scripts and Special Actions to identify a THING or set of THINGs
0	2	short	X-position on the map at inception of level.
2	4	short	Y-position on the map at inception of level.
-	6	short	Starting height: the THING is created at this height above the floor of the it's in at inception of the level, and immediately subjected to gravity.
4	8	short	Facing angle at inception of level.
6	10	short	THING type.
8	12	short	THING attribute flags.
-	14	byte	Special type: activated when the thing is killed, destroyed or picked up (depending upon type). Some THINGS cannot use a Special.
-	15	5 bytes	Special's arguments; or THING operational parameters.

 

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 Facing Angle

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A THING's facing angle is the way it faces at the inception of the level. On the automap, 0 is east, 90 is north, 180 is west, 270 is south. Note that values are rounded to the nearest 45 degree angle, so if the value is 80, it will actually face 90 - north. (In Hexen, do not confuse these facing angle values with the Angle parameter used in certain Specials where a different scheme is used.)

In DOOM, this field of the THING structure is only used for monsters, player starts, deathmatch starts, and teleporter landing spots. All other things look the same from all directions.

 

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 THING Attribute (or Option) Flags

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The THING attribute short consists of a series of bit-wise flags, which operate as follows: (bits not listed are unused)

THING option flags
Bit	Meaning when Set
0	appears at skill settings 1 and 2
1	appears at skill settings 3
2	appears at skill settings 4 and 5
3	deaf guard--a monster with this bit set will remain asleep until activated by seeing a player, or being hit with weapons fire (from player or other monster).
4	(Not Hexen) appears only in multiplayer mode.
4	(Hexen only) Dormant--remains asleep until activated with a Thing_Activate special.
5	(Hexen only) appears for the Fighter class.
6	(Hexen only) appears for the Cleric class.
7	(Hexen only) appears for the Mage class.
8	(Hexen only) appears in single-player games.
9	(Hexen only) appears in co-operative games.
10	(Hexen only) appears in deathmatch games.

Skill setting appearances

Bits 0, 1 and 2 control whether or not any given THING will appear when the WAD is played at a particular skill level setting. Note that these bits may be used perfectly independantly of each other, so it is possible to arrange for an item or monster to be present at skill levels 1, 2, 4 and 5 but be absent when playing at skill level 3.

Deaf and dormant guards

Also known as the "ambush" bit, the setting of bit 3 only has meaning for monsters. Any with this bit set will not awaken until they see a player or are hit by weapons fire from players or other monsters. Monsters without this bit set will activate when they hear gunshots, etc (including the punch). (Note that sound does not travel through walls that are solid at the time the noise was made, and that lines can be set so that sound does not pass through them--see the Blocks Sound flag.)

Dormant guards are a feature new to Hexen. These monsters require a Thing_Activate special to awaken them.

Hexen Player-Class appearances

To cater for variations due to Hexen's three player Class settings, Hexen provides three new flags which control whether or not particular items are present when playing as Fighter, Cleric or Mage. These flags can be set independantly of each other.

Multi-player game appearances

In DOOM, individual THINGS can be flagged to appear only in the multi-player modes (Co-operative and Deathmatch) play. This is mostly used to trigger the appearance of extra weapons and ammunition in those modes, or to block off certain passages with obstacles. Note that in DOOM, DOOM II and Heretic it is not possible to arrange for particular items to appear only in single-player mode.

Hexen provides much more flexible control over the appearance of THINGS in multi-player games by replacing DOOM's single bit with three new ones that can be manipulated independantly of each other. For multi-player games involving more than one class of player, an item which is set for one of the classes involved will also appear for the other classes in the game so that all players see the same things.

 

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 THING Types

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A THING's type value is what determines what kind of item will be represented in the game at the specified location on the map. Not surprisingly, each version of the game has its own set of THING types. More details are available on:

• DOOM/DOOM II THINGS
• Heretic THINGS
• Hexen THINGS

 

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 Hexen THING Special

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Hexen has extended the triggering of Special Actions by adding a Special attribute to THINGS. Offset 14 of a Hexen THING provides a byte value which specifies a Special Action to be activated when the particular THING is killed (Monster), destroyed (Destructible Object) or picked up (Artifact, Puzzle Piece). Also, if a creature has a special and is teleported away using the Banishment Device, its Special is activated and then removed from the creature.

The specified action can take up to five arguments, supplied by the five bytes following the THING Special. The actions triggered are generally the same as those triggered by LINEDEF Specials, although some act on the THING itself.

Some types of THING use the five Special Argument bytes to control their own operation and consequently will ignore any value specified in their Special. (This is not the restriction it sounds: these are not the kind of things whose Special could be activated anyway!) [Details]

 

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 Activating/deactivating Hexen THINGS

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The activation of THINGs in Hexen is more flexible than in DOOM, DOOM II or Heretic: creatures as well as some objects (classed as Activatable THINGS) can be activated with the Thing_Activate Special action and deactivated with the Thing_Deactivate. Creatures freeze when deactivated and resume when activated: other activatable objects begin or cease an animation sequence, or change state. This method of activation is also used to bring a "dormant" Monster to life.

 

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