DECORATE expressions

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DECORATE supports complex mathematical expressions as parameters for codepointers. (Unfortunately, expressions are not supported for the values of properties.) The expression may include standard operators (+, -, *, /, <<, >>, |, etc.), math functions, and certain actor properties (occasionally called “keywords” in the forums) to compare values with. A_JumpIf, in particular, is meant to be used with expressions, but they can be used for any numeric (integer or floating point) parameter. For example, using velx, vely, and velz in A_SpawnItemEx to preserve velocity, or using args[] as arguments to a call of ACS_Execute.

Mathematical functions

  • abs(x) — returns the absolute value of x.
  • exp(x) - Returns the base-e exponential function of x, which is e raised to the power x: ex .(development version a862f72 only)
  • log(x) - Returns the natural logarithm of x -- the opposite of exp. (development version a862f72 only)
  • log10(x) - Returns the common (base-10) logarithm of x. (development version a862f72 only)
  • ceil(x) - Rounds x upward to the next closest integral value. Result is still floating point. (development version a862f72 only)
  • floor(x) - Rounds x down to the next closest integral value. Result is still floating point. (development version a862f72 only)
  • sqrt(x) — Returns the square root of x.
  • min(float or int, ...) - Gets the smallest value of all values listed. Can take any amount of numbers, and can solve both ints and floats. (development version 1ffb7ad only)
  • max(float or int, ...) - Gets the largest value of all values listed. Can take any amount of numbers, and can solve both ints and floats. (development version 1ffb7ad only)
  • clamp(src, min, max) - Returns src within the range of min and max inclusively. All parameters can be ints or floats. (development version fd78686 only)

Trigonometry functions

Randum number functions

  • random[identifier](min, max) — returns a random integer value between min and max
  • random2[identifier](mask) — returns a random integer value between -mask and +mask. It is roughly equivalent to random(0, mask) - random(0, mask). If no mask is provided (random2()), the maximum value of 255 is used instead. Mask is used as a binary mask, e.g. if 9 is used, the random results can be [0, 1, 8, 9] - [0, 1, 8, 9], so it is advised to use as a mask values one less than a power of two, such as 1, 3, 7, 15, 31, 63, or 127.
  • frandom[identifier](min, max) — returns a random floating point value between min and max
  • randompick[identifier](int, ...) — picks a number from the numbers placed in it. This can take an unlimited amount of parameters, i.e. randompick(1, 4, 12, 16) will choose one of the four numbers.(New from 2.8.1)
  • frandompick[identifier](float, ...) — similar to randompick but for float-point values. (New from 2.8.1)

identifier is optional. Calls to a random function with an identifier do not interfere with the RNG for calls with a different identifier, which can be used to make the outcome of some events unaffected by others.

ACS functions

DECORATE functions

These functions are not like regular DECORATE action functions. They can be used just like expressions (i.e. randompick) inside of action functions directly such as A_SetUserVar.


There are a few variables you can use for dynamic data in DECORATE definitions. These are:

Actor position and movement
  • x — The actor's X position in the world.
  • y — Same, but for Y.
  • z — Same, but for Z.
  • angle — Actor's angle, in degrees
  • ceilingz — See GetActorCeilingZ
  • floorz — See GetActorFloorZ
  • pitch — The actor's pitch in degrees.
  • roll - The actor's roll. Currently, this only really affects players such as the rotation of view. (New from 2.8.1) Graficon.gif (GZDoom only: not supported by ZDoom)
  • velx or momx — Actor's velocity along the absolute X axis. The "mom" names are (deprecated).
  • vely or momy — Same, but for Y.
  • velz or momz — Same, but for Z.
Actor properties
  • accuracy — The accuracy of the Actor.
  • alpha — The Alpha value of the Actor.
  • args[] — Arguments passed to the thing special; args[0] through args[4] are valid.
  • damage — The actor's Damage.
  • health — How much health the Actor has left.
  • height — The actor's Height.
  • mass — The actor's Mass.
  • meleerange — The actor's MeleeRange.
  • radius — The actor's Radius.
  • reactiontime — The actor's ReactionTime.
  • scaleX — The actor's horizontal scale. See A_SetScale.
  • scaleY — The actor's vertical scale. See A_SetScale.
  • score — The actor's score.
  • special — ID of the special currently assigned to this actor.
  • speed — The actor's Speed. (New from 2.8.1)
  • stamina — The stamina of the Actor.
  • tid — The actor's TID.
  • tidtohate — TID of the current assigned target. (see Thing_Hate.)
  • threshold — The actor's Threshold. (development version c940c2b only)
  • defthreshold — The actor's DefThreshold. (development version 43b4d45 only)
  • Constant VariablesConstant variables can be defined both inside and outside of an actor.
  • User Variablesuser variables are defined as "var int user_(name);" in actor properties.
  • User Arrays — user arrays are defined as "var int user_(name)[(size)];" in actor properties.
  • waterlevel — How "submerged" the actor is in a Transfer_Heights or 3D floor water pool:
0: Not submerged at all (e.g. standing on solid ground or on shallow TERRAIN-based water)
1: Less than half submerged ("ankle deep")
2: At least half submerged ("waist deep")
3: Entirely submerged (completely underwater)


See Projectile Trap