From ZDoom Wiki
Jump to: navigation, search
Note: This feature is for ZScript only.

A Thinker class is derived from Object, and is used as the base for an Actor and more. Unlike actors, thinkers are not physically present in the game at all.

Thinkers are generally used to 'run the game' -- movement, shooting, performing functions, etc.

Thinkers do not possess the many properties and functions an actor has, drastically cutting down on the amount of overhead generated from creating an actor. As such, these make excellent candidates for replacing dummy actors used to monitor and modify primary actors.


The engine utilizes stat numbers on thinkers to organize thinkers and whether to call their Tick() functions or not.

Some have special use cases such as the STAT_CORPSEPOINTER, invoked by A_QueueCorpse, which creates a thinker for the calling actor, utilizing internal code to eliminate corpses as the queue when filled.

Because of the aforementioned internal handling, take caution when changing a stat number. The engine may manipulate them at any time and cause issues. Thinkers also can only belong to one stat category at any time.

The safest ranges to use are anywhere under 127, and the unmentioned numbers not defined in the list below (i.e. 99, 98, etc -- so long as they are not defined internally).

NOTE: Not all thinkers will actually use their Tick() virtuals based on their stat numbers (see below under the comment 'Thinkers that don't actually think'). It's possible to have another thinker manually call the non-ticking thinker's Tick function inside its own.

Internal Code

class Thinker : Object native play
	enum EStatnums
 		// Thinkers that don't actually think
		STAT_INFO,							// An info queue
		STAT_DECAL,							// A decal
		STAT_AUTODECAL,							// A decal that can be automatically deleted
		STAT_CORPSEPOINTER,						// An entry in Hexen's corpse queue
		STAT_TRAVELLING,						// An actor temporarily travelling to a new map
		STAT_STATIC,							// Will remain available after exiting a level -- normally destroyed otherwise.

		// Thinkers that do think
		STAT_PLAYER,							// A player actor
		STAT_BOSSTARGET,						// A boss brain target
		STAT_LIGHTNING,							// The lightning thinker
		STAT_DECALTHINKER,						// An object that thinks for a decal
		STAT_INVENTORY,							// An inventory item
		STAT_LIGHT,							// A sector light effect
		STAT_LIGHTTRANSFER,						// A sector light transfer. These must be ticked after the light effects.
		STAT_EARTHQUAKE,						// Earthquake actors
		STAT_MAPMARKER,							// Map marker actors
		STAT_DLIGHT,							// Dynamic lights

		STAT_DEFAULT = 100,						// Thinkers go here unless specified otherwise.
		STAT_SECTOREFFECT,						// All sector effects that cause floor and ceiling movement
		STAT_ACTORMOVER,						// actor movers
		STAT_SCRIPTS,							// The ACS thinker. Ensures it can't tick before all actors call PostBeginPlay
		STAT_BOT,							// Bot thinker

	const TICRATE = 35;
	virtual native void Tick();
	virtual native void PostBeginPlay();
	virtual native void ChangeStatNum(int stat);
	static clearscope int Tics2Seconds(int tics)
		// This compensates for one tic being slightly less than 1/35 of a second.
		return int(tics * (0.98 / TICRATE));