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 (+, -, *, /, <<, >>, |, ? and : (ternary) 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 .
  • log(x)
Returns the natural logarithm of x -- the opposite of exp.
  • log10(x)
Returns the common (base-10) logarithm of x.
  • ceil(x)
Rounds x upward to the next closest integral value. Result is still floating point.
  • floor(x)
Rounds x down to the next closest integral value. Result is still floating point.
  • round(x)
Rounds x to the closest integral value. Result is still floating point.
  • 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.
  • 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.
  • clamp(src, min, max)
Returns src within the range of min and max inclusively. All parameters can be ints or floats.

Trigonometry functions

  • cos(x)
  • sin(x)
  • tan(x)
Returns cosine, sine, or tangent of angle x. x must be in degrees.
  • acos(x)
  • asin(x)
  • atan(x)
Returns the inverse cosine, sine, or tangent of x. Returns an angle in degrees.
  • cosh(x)
  • sinh(x)
  • tanh(x)
Returns the hyperbolic cosine, sine, or tangent of x.
  • atan2(y, x)
Similar to atan, but used to get the quadrants the angles are in. Returns in degrees.
  • VectorAngle(x, y)
Like atan2, only with x first instead of y. Can be used to calculate an angle, for example, by passing coordinates to it.
VectorAngle(user_x[0] - user_x[1], user_y[0] - user_y[1])

Random 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 equivalent to (random() & mask) - (random() & mask). If no mask is provided, i.e, 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.
  • frandompick[identifier](float, ...)
Similar to randompick but for float-point values.
  • SetRandomSeed[identifier](seedvalue)
Used if a guaranteed sequence of random numbers is desired. When a specific number is set as seed, the random-number generator (RNG) will always produce the same numbers. Useful for cases where an RNG may be used for purposes where total randomness is not wanted.

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

Runs a script and uses its return value.
Runs a named script and uses its return value.
Shorter alias for ACS_NamedExecuteWithResult.

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.

Checks an actor's class name, returning true if it matches the passed parameter.
Gets the number of inventory items an actor is holding from a pointer and returns it to the expression.
Similar to A_CheckProximity but returns how many of the actors are found instead of jumping.
Gets the angle which an actor pointer can be found at. Can toggle the relative functionality
Gets a server cvar, internal or user.
Gets the current crouch factor of a player if the player is a pointer.
Gets the distance from the calling actor to a pointer. Can toggle the Z checking functionality.
Gets the gib health property of the calling actor.
Gets the damage of the actor.
Performs the same functionality as the ACS GetPlayerInput.
Gets the spawn health property of the calling actor.
Gets an Actor pointer's sprite angle.
Gets an Actor pointer's sprite rotation.
Gets the Z coordinate of a floor or ceiling at a specific set of coordinates.
Compares two actor pointers, returning true if they reference the same actor.
  • OverlayID()
When used in an overlay, it retrieves the overlay's layer index.
Returns the x position of the specified overlay.
Returns the y position of the specified overlay.
Sets the actor's damage.


As of GZDoom 2.2.0, it is possible to directly modify some of the variables with assignment operators.

  • Bold - Read and write variables. Allows direct assignment operators.
  • Italics - Read-only variables.

Read-only variables must still rely upon the action function used to manipulate them (e.g. A_Warp for x/y/z, A_ChangeVelocity for velx/vely/velz). As of GZDoom 2.2.0, unary increment/decrement operators (user_test++, --user_test, etc.) may be used, as well.

NOTE: Direct variable modifications will not be interpolated or have any other effects performed upon them. If these effects are desired, use the action function associated with the variable(s) instead (such as A_SetAngle for interpolating angle changes).

The following is dynamic data for use in DECORATE definitions and expressions:

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 — returns Z height of the ceiling above the calling actor as an absolute double value (portal- and 3D-floor-aware)
  • floorz — returns Z height of the floor underneath the calling actor as an absolute double value (portal- and 3D-floor-aware)
  • pitch — The actor's pitch in degrees.
  • roll - The actor's roll. Currently, this only really affects players such as the rotation of view.
  • 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. (deprecated)
  • 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.
  • 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.
  • defthreshold — The actor's DefThreshold.
  • VisibleStartAngle/VisibleEndAngle - The actor's angle range which the camera must see it to draw the sprite. Requires MASKROTATION flag to have any effect.
  • VisibleStartPitch/VisibleEndPitch - Same as VisibleStartAngle and VisibleEndAngle but for pitch instead.
  • 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)
  • waterdepth — The exact depth that the actor is at inside of a Transfer_Heights or 3D floor water volume. Returns an floating point number. Can be used for more detailed depth checks than waterlevel.


See Projectile Trap