# Entitydef (decl)

Entity definitions are simply a list of key/value pairs or spawn arguments.

When the engine spawns an entity , the entityDef is looked up to build the spawnArgs dictionary of the spawn class .

So entityDefs conceptually define the default attributes of an entity - in combination with the key/value pairs for the map entity set in the level editor.

## Syntax

entityDef [entitydeftype] {
[key_1] [value_1]
[key_2] [value_2]
[key_3] [value_3]
...
}

Entity definitions begin with a header which consists of the keyword “entityDef” followed by the name of the entityDef type.

The header is followed by the body of the declaration which is enclosed in curly brackets.

The body is composed of a series of keys and values. Keys and values are enclosed by quotation marks.

## Important Key/Values

While most of the key/value pairs are just data to be used by the entity spawn class, script object or level script there are a few that should be mentioned.

"inherit" [entitydef type]

The “inherit” key/value pair can be used in any entity definition. It’s purpose is to instruct the engine to inherit key/value pairs from the specified entityDef type to reduce redundancy.

"spawnclass" [spawn class type]

The spawnclass key/value pair defines the spawn class type of this entity. An entity will fail to spawn if it doesn’t have a spawnclass key/value set via an entityDef or map entity .

"scriptobject" [script object type]

The “scriptobject” key/value pair key/value pair is used to assign a script object type to this entity type to control its behavior.

## Inheritance and Spawn Classes Example

Using a paraphrased snippet from the monster_zombie_fat entity definition in Doom 3:

entityDef monster_zombie_fat {
"inherit"       "zombie_default"
"scriptobject"      "monster_zombie"
"size"          "48 48 68"
"use_aas"       "aas48"
"team"          "1"
"rank"          "0"
"health"        "100"
"melee_range"       "32"
"walk_on_sight"     "1"
"mass"          "200"
...
}

Here, the inherit value means is that when the monster_zombie_fat is looked up it will be combined with the key/value pairs defined in zombie_default.

By looking at zombie_default we can see the key/value pairs that are inherited:

entityDef zombie_default {
"inherit"       "monster_default"
...
}

Notice that this entity definition also inherits key/value pairs from another entityDef, in this case from monster_default:

entityDef monster_default {
"editor_color"      "1 .5 0"
"editor_mins"       "-24 -24 0"
"editor_maxs"       "24 24 64"
"editor_showangle"  "1"
"editor_copy"       "anim"
...
"spawnclass"        "idAI"
...
}

And at this point the inheritance stops because there is no other “inherit” key/value pair. However, there is a “spawnclass” key/value pair. In this example the spawn class idAI.

## Script Objects Example

In this example, the scriptobject key/value is defining what AI script object type to use to control this entity.

entityDef monster_zombie_fat {
"inherit"       "zombie_default"
"scriptobject"      "monster_zombie"
"size"          "48 48 68"
"use_aas"       "aas48"
"team"          "1"
"rank"          "0"
"health"        "100"
"melee_range"       "32"
"walk_on_sight"     "1"
"mass"          "200"
...
}

## Practical Example

If you wanted to create a new type of monster_zombie_fat with a health value of 200 you simply create a new entity definition that inherits from monster_zombie_fat and set a new health key/value pair…

entityDef monster_zombie_fat_200 {
"inherit"       "monster_zombie_fat"
"health"        "200"
}