The .animated object format

■ Contents

■ 1. Overview

The ANIMATED object format is a container format allowing you to reference other objects (B3D/CSV/X) and to apply animation to them. It also allows to just group other objects (including other ANIMATED objects) without animating them.

Animated objects can be used in CSV/RW routes (unless explicitly disallowed by some commands), as train exterior objects via the extensions.cfg, and as 3D cabs via the panel.animated file.

● Basics

Animation is performed via the following primitives:

● A little formality

The file is a plain text file encoded in any arbitrary encoding, however, UTF-8 with a byte order mark is the preferred choice. The parsing model for numbers is Strict. The file name is arbitrary, but must have the extension .animated. The file is interpreted on a per-line basis, from top to bottom.

■ 2. Sections

● The [Include] section

You can use the [Include] section to just include other objects, but without animating them. This allows you to use the ANIMATED object file as a container to group other objects. There can be any number of [Include] sections within the file.

[Include]


This starts the section.

FileName0
FileName1
FileName2


Defines a series of B3D/CSV/X/ANIMATED objects that should be included as-is.

Position = X, Y, Z


This defines the position of the objects, basically allowing you to offset them with respect to the rest of the ANIMATED object file.


● The [Object] section

You can use the [Object] section to create a single animation. This requires to set up at least one state via the States parameter, and to use any combination of functions you want, which provide control over the animation. There can be any number of [Object] sections within the file.

[Object]


This starts the section.

Position = X, Y, Z


Defines the position of the object. This basically corresponds to a final TranslateAll command in the respective CSV/B3D file, but is performed after any of the functions are performed. For example, if you want to use rotation, then keep in mind that rotation is done around the origin (0,0,0). The Position command allows you to reposition the object after the rotation is performed.

States = File0, File1, …, Filen-1


Loads n objects of CSV/B3D/X extension. Please note that the first file indicated has state index 0. Use multiple files only if you want to use state changes.

StateFunction = Formula


This defines the function for state changes. The result of the Formula is rounded toward the nearest integer. If that integer is between 0 and n-1, where n is the number of states as defined via States, the respective state is shown, otherwise, no object is shown. You can make use of the latter if you want an object to toggle on/off with only one state.

TranslateXDirection = X, Y, Z
TranslateYDirection = X, Y, Z
TranslateZDirection = X, Y, Z


These define the directions for the TranslateXFunction, TranslateYFunction and TranslateZFunction, respectively. The default directions are:

TranslateXDirection = 1, 0, 0
TranslateYDirection = 0, 1, 0
TranslateZDirection = 0, 0, 1

This means that TranslateXFunction will move right by default, TranslateYFunction up and TranslateZFunction forward, which is also why TranslateXFunction and so on bear their names. If you define other directions, then simply think of the three functions and associated directions as three independent ways to move the object in that direction.

TranslateXFunction = Formula
TranslateYFunction = Formula
TranslateZFunction = Formula


These define the functions to move the object into the respective direction. The Formula needs to return the amount of meters to move from the initial position. The X, Y and Z parameters in the respective direction are multiplied by the result of Formula, so you could for example either multiple the formula by 2 or the direction by 2 if you want to double the speed of movement.

RotateXDirection = X, Y, Z
RotateYDirection = X, Y, Z
RotateZDirection = X, Y, Z


These define the directions for the RotateXFunction, RotateYFunction and RotateZFunction, respectively. The default directions are:

RotateXDirection = 1, 0, 0
RotateYDirection = 0, 1, 0
RotateZDirection = 0, 0, 1

This means that RotateXFunction will rotate around the x-axis by default, RotateYFunction around the Y-axis, and RotateZFunction around the z-axis, which is also why RotateXFunction and so on bear their names. If you define other directions, then simply think of the three functions and associated directions as three independent ways to rotate the object.

RotateXFunction = Formula
RotateYFunction = Formula
RotateZFunction = Formula


These define the functions to rotate along the respective direction in counter-clockwise order. The Formula needs to return the angle by which to rotate in radians. The order in which the rotations are performed is: RotateXFunction (first), RotateYFunction (then) and RotateZFunction (last). If you use more than one rotation function at a time, bear this order in mind. If necessary, overwrite the default directions for the rotations if you need a different order.

RotateXDamping = NaturalFrequency, DampingRatio
RotateYDamping = NaturalFrequency, DampingRatio
RotateZDamping = NaturalFrequency, DampingRatio


These define damping for the corresponding functions. If not used, damping will not be performed. NaturalFrequency is a non-negative value corresponding to the angular frequency of an assumed undamped oscillator in radians per second. DampingRatio is a non-negative value indicating the type of damping. Values between 0 and 1 represent under-damping, 1 represents critical damping, and values above 1 represent over-damping.

TextureShiftXDirection = X, Y
TextureShiftYDirection = X, Y


These define the directions for the TextureShiftXFunction and TextureShiftYFunction, respectively. The default directions are:

TextureShiftXDirection = 1, 0
TextureShiftYDirection = 0, 1

This means that TextureShiftXFunction will shift the texture right by default, and TextureShiftYFunction down, which is also why TextureShiftXFunction and so on bear their names. If you define other directions, then simply think of the two functions and associated directions as two independent ways to shift textures on the objects.

TextureShiftXFunction = Formula
TextureShiftYFunction = Formula


These define the functions to shift the texture in the respective direction. The texture is shifted by the return value of Formula in texture coordinates. The integer part of the result is ignored, and a fractional part of 0.5 represents moving the texture half way. The SetTextureCoordinate commands in the object file define the coordinates, which are then added the outcome of these formulas.

TrackFollowerFunction = Formula


This defines the function which moves an object along the path of Rail 0. Formula must return a distance in meters, for which the object is then moved, respecting the curves and height changes of Rail 0.

TextureOverride = Value


Value = Timetable: All faces will show the timetable bitmap as set up by CSV/RW routes.
Value = None: The original textures will be displayed on the faces (default behavior).

RefreshRate = Seconds


This defines the minimum amount of time that needs to pass before the functions are updated. A value of 0 forces the functions to be updated every frame. Please note that objects outside of the visual range might be updated less frequently regardless of this parameter. Use RefreshRate when you don’t need a perfectly smooth animation (in order to optimize performance), or when you deliberately want the object to be only updated in fixed intervals.


● The [Sound] section

You can use the [Sound] section to add standalone sound effects to animated objects.

[Sound]


This starts the section.

FileName = File


This loads the sound effect to play.

Position = X, Y, Z


Defines the position of the sound, relative to the center of the animated file.

Volume = Value

This defines the initial volume of the sound at the source position. A value of 1.0 represents the nominal unchanged volume of the sound file.

Pitch = Value

This defines the initial pitch of the sound at the source position. A value of 1.0 represents the nominal unchanged pitch of the sound file.

Radius = Value

This defines the radius in meters from it’s source at which the sound effect plays at full volume. The default value is 30.

VolumeFunction = Formula


This defines the function which controls the volume of the sound. Formula must return a number representing the desired volume, where 1.0 represents the nomimal unchanged volume of the sound file.

PitchFunction = Formula


This defines the function which controls the pitch of the sound. Formula must return a number representing the desired pitch, where 1.0 represents the nomimal unchanged pitch of the sound file.

TrackFollowerFunction = Formula


This defines the function which moves the source of the sound along the path of Rail 0. Formula must return a distance in meters, for which the object is then moved, respecting the curves and height changes of Rail 0.


● The [StateChangeSound] section

You can use the [StateChangeSound] section to attach sound effects to the preceeding [Object] section.

[StateChangeSound]


This starts the section- Must immediately follow an [Object] section.

FileName = File


This loads the sound effect to play for all state changes. Alternatively, FileNames may be used, which is described below:

FileNames = File0, File1, …, Filen-1


Loads a list of n sounds, which correspond to the states in the [Object] section above. If a state is to have no sound effect, the list entry should be left blank.

Position = X, Y, Z


Defines the position of the sound, relative to the center of the animated file.

Volume = Value

This defines the volume of the sound at the source position. A value of 1.0 represents the nominal unchanged volume of the sound file.

Pitch = Value

This defines the pitch of the sound at the source position. A value of 1.0 represents the nominal unchanged pitch of the sound file.

Radius = Value

This defines the radius in meters from it’s source at which the sound effect plays at full volume. The default value is 30.

PlayOnShow = Value

Value = 0: The sound effect will not be played. Value = 1: The sound effect will be played.

This defines whether the sound effect defined above should be played when a the relevant state is shown.

PlayOnHide = Value

Value = 0: The sound effect will not be played. Value = 1: The sound effect will be played.

This defines whether the sound effect defined above should be played when the relevant state is hidden.


openBVE 2 compatibility note

During the development of openBVE (v0.9) and during the development of the animated object format, there were certain commands in existance ending in RPN, such as TranslateXFunctionRPN. These commands never made it into any official release (v1.0) and were thus never meant to be used outside of development environments. While they are still available undocumentedly, they will be removed for openBVE 2. If you are using these commands, please get rid of them as soon as possible.


● About the formulas

First of all, infix notation, which is what you can enter for Formula, is converted into functional notation. Thus for every infix notation, there is a corresponding functional notation. Some functions do not have an infix operator and can thus only be entered in functional notation. For operators, precedence plays an important role. You can use parantheses to override the order of precedence just as in any usual mathematical formula. Names of functions are case-insensitive.

Please note that if the result of any mathematical operation or function would be infinity, indeterminate or non-real, 0 is returned. Numeric overflow is not prevented, so you need to take that into account yourself.

■ 3. List of infix notation operators

● Basic arithmetics
Infix Functional Description
a + b Plus[a,b, ...] Represents addition
a - b Subtract[a,b] Represents subtraction
-a Minus[a] Negates the number
a * b Times[a,b,...] Represents multiplication
a / b Divide[a,b] Represents division
● Comparisons

All comparisons return 1 for true and 0 for false.

Infix Functional Description
a == b Equal[a,b] True (1) if a equals b
a != b Unequal[a,b] True (1) if a does not equal b
a < b Less[a,b] True (1) if a is less than b
a > b Greater[a,b] True (1) if a is greater than b
a <= b LessEqual[a,b] True (1) if a is less than or equal to b
a >= b GreaterEqual[a,b] True (1) if a is greater than or equal to b
● Logical operations

All operations treat 0 as false and any other value as true, and return 1 for true and 0 for false.

Infix Functional Description
!a Not[a] True (1) if a is false
a & b And[a,b] True (1) if both a and b are true
a | b Or[a,b] True (1) if any of a or b are true
a ^ b Xor[a,b] True (1) if either a or b is true
● Operator precedence

From highest precedence to lowest. Operators of same precedence are evaluated left to right in the order in they occur in the formula.

a[...]
- (Minus)
/
*
+, - (Subtract)
==, !=, <, >, <=, >=
!
&
^
|


Please note that some combinations of prefix and infix operators are not recognized. For example a*-b is not accepted. Use a*(-b) or -a*b instead.

■ 4. List of functions

● Basic arithmetics
Function Description
Reciprocal[x] Returns the reciprocal, equal to 1/x
Power[a,b,...] Returns a raised to the bth power. b must be a non-negative number. For consistency, Power[0,b] always returns 1, even in the degenerate case Power[0,0], and a being negative always returns 0. Adding more arguments will create a chain. Power[a,b,c] will return abc.
● Numeric functions
Function Description
Quotient[a,b] Divides a by b and rounds the result down, equal to Floor[a/b].
Mod[a,b] Returns the remainder of dividing a by b, equal to a-b*Floor[a/b].
Min[a,b,...] Returns the smallest of the terms.
Max[a,b,...] Returns the largest of the terms.
Abs[x] Returns the absolute value.
Sign[x] Returns the sign of x, which is either -1, 0 or 1.
Floor[x] Rounds down to the nearest integer.
Ceiling[x] Rounds up to the nearest integer.
Round[x] Rounds to the nearest integer. Numbers ending in .5 are rounded to the nearest even integer.
random[Minimum, Maximum] Returns a new random floating-point number between Minimum and Maximum.
randomInt[Minimum, Maximum] Returns a new random integer between Minimum and Maximum.
● Elementary functions
Function Description
Exp[x] The exponential function, or e to the xth power.
Log[x] The natural logarithm, to base e.
Sqrt[x] The square root.
Sin[x] The sine (input in radians).
Cos[x] The cosine (input in radians).
Tan[x] The tangent (input in radians).
ArcTan[x] The inverse tangent (output in radians).
● Conditionals
Function Description
If[cond,truevalue,falsevalue] If cond is != 0, returns truevalue, otherwise falsevalue

■ 5. List of variables

● Primitives
Variable Description
value The value returned by the function in the last evaluation. At the beginning of the simulation, this is 0.
delta The time difference since the last evaluation of the function in seconds. Please note that there is no guaranteed time that elapses between successive function calls.
currentState Returns the current numerical state of the object.
● Time and camera
Variable Description
time The current in-game time measured in seconds since midnight of the first day.
cameraDistance The non-negative cartesian distance measured from the object to the camera in meters.
cameraMode Returns 0 if the camera is currently in a 2D or 3D cab, 1 otherwise.
● Trains

Generally, objects attached to a particular train and car return values for that train and car, unless stated otherwise. For scenery objects, the reference is the driver’s car of the nearest train (not necessarily the player’s train).

In some of the following variables, carIndex has the following meaning: 0 is the 1st car from the front, 1 is the 2nd car from the front, etc., while -1 is the 1st car from the rear, -2 is the 2nd car from the rear, etc. In general, car indices from -cars to cars-1 represent existing cars, where cars is the number of cars the train has, while values outside of this range represent non-existing cars. As all trains have at least 1 car, indices -1 and 0 are guaranteed to exist for any train.

● Trains (general)
Variable Description
cars The number of cars the train has.
speed The signed actual speed of the current car in m/s. Is positive when the train travels forward, and negative when the train travels backward.
speed[carIndex] The signed actual speed of the car carIndex in m/s. Is positive when the train travels forward, and negative when the train travels backward.
speedometer The signed perceived speed of the current car in m/s as it would appear to a speedometer on wheel slip and wheel lock.
speedometer[carIndex] The signed perceived speed of the car carIndex in m/s as it would appear to a speedometer on wheel slip and wheel lock.
acceleration The actual acceleration of the current car in m/s².
acceleration[carIndex] The actual acceleration of the car carIndex in m/s².
accelerationMotor The acceleration which the motor of the first motor car currently generates in m/s².
accelerationMotor[carIndex] The acceleration which the motor of the car carIndex currently generates in m/s².
distance The non-negative cartesian distance measured from the object to the closest car in meters. Only meaningful for scenery objects.
distance[carIndex] The non-negative cartesian distance measured from the object to the car carIndex in meters, or 0 if the car does not exist. Only meaningful for scenery objects.
trackDistance The signed track distance measured from the object to the closest end of the nearest train in meters. Is positive when the train is in front of the object, negative when behind, and zero when the object lies between the ends of the train.
trackDistance[carIndex] The signed track distance measured from the object to the car carIndex of the nearest train in meters. Is positive when the center of the car is in front of the object, and negative if behind. Returns 0 if the car does not exist. Only meaningful for scenery objects.
destination The currently set destination for this train. (Set via Track.Destination or the plugin interface)
distanceNextStation The distance in m to the next station.
distanceStation[stationIndex] The distance in m to the station with stationIndex
stopsNextStation Whether the train stops at the next station.
stopsStation[stationIndex] Whether the train stops at the station with stationIndex
nextStation The index of the next station.
nextStationStop The index of the next station where the train must stop.
● Trains (brake)
Variable Description
mainReservoir The current pressure in the main reservoir in this car, measured in Pa.
mainReservoir[carIndex] The current pressure in the main reservoir in car carIndex, measured in Pa.
emergencyReservoir The current pressure in the emergency reservoir in this car, measured in Pa.
emergencyReservoir[carIndex] The current pressure in the emergency reservoir in car carIndex, measured in Pa.
brakePipe The current pressure in the brake pipe in this car, measured in Pa.
brakePipe[carIndex] The current pressure in the brake pipe in car carIndex, measured in Pa.
brakeCylinder The current pressure in the brake cylinder in this car, measured in Pa.
brakeCylinder[carIndex] The current pressure in the brake cylinder in car carIndex, measured in Pa.
straightAirPipe The current pressure in the straight air pipe in this car, measured in Pa.
straightAirPipe[carIndex] The current pressure in the straight air pipe in car carIndex, measured in Pa.
● Trains (doors)
Variable Description
doors The state of the doors. Returns 0 if fully closed, 1 if fully opened, or any intermediate value, biasing doors that are in a more open state.
doors[carIndex] The state of the doors of car carIndex. Returns 0 if fully closed, 1 if fully opened, or any intermediate value, biasing doors that are in a more open state.
leftDoors The state of the left doors. Returns 0 if fully closed, 1 if fully opened, or any intermediate value, biasing doors that are in a more open state.
leftDoors[carIndex] The state of the left doors of car carIndex. Returns a value between 0 and 1, biasing doors that are in a more open state, or -1 if the car does not exist.
rightDoors The state of the right doors. Returns 0 if fully closed, 1 if fully opened, or any intermediate value, biasing doors that are in a more open state.
rightDoors[carIndex] The state of the right doors of car carIndex. Returns a value between 0 and 1, biasing doors that are in a more open state, or -1 if the car does not exist.
leftDoorsTarget The anticipated target state of the left doors. Returns either 0 (closed) or 1 (opened).
leftDoorsTarget[carIndex] The anticipated target state of the left doors of car carIndex. Returns either 0 (closed) or 1 (opened).
rightDoorsTarget The anticipated target state of the right doors. Returns either 0 (closed) or 1 (opened).
rightDoorsTarget[carIndex] The anticipated target state of the right doors of car carIndex. Returns either 0 (closed) or 1 (opened).
leftDoorsButton The state of the left doors button. Returns either 0 (released) or 1 (pressed).
rightDoorsButton The state of the right doors button. Returns either 0 (released) or 1 (pressed).
pilotLamp The state of the pilot lamp (Doors closed & ready to start). Returns either 0 (unlit) or 1 (lit).
● Trains (miscellaneous)
Variable Description
reverserNotch The state of the reverser, which is either -1 (backward), 0 (neutral), or forward (1).
powerNotch The current power notch, i.e. 0 for N, 1 for P1, 2 for P2, 3 for P3, etc.
powerNotches The amount of power notches the train has.
brakeNotch The current brake notch.
● For trains without the automatic air brake: 0 for N, 1 for B1, 2 for B2, 3 for B3, etc.
● For trains with the automatic air brake: 0 for REL, 1 for LAP and 2 for SRV.
brakeNotches The amount of brake notches the train has. For trains with the automatic air brake, this returns 2.
brakeNotchLinear A combination of brake notch, hold brake and emergency brake.
● For trains without the automatic air brake and without hold brake: 0 for N, 1 for B1, 2 for B2, 3 for B3, etc., up to BrakeNotches+1 for EMG.
● For trains without the automatic air brake but with hold brake: 0 for N, 1 for HLD, 2 for B1, 3 for B2, 4 for B3, etc., up to BrakeNotches+2 for EMG.
● For trains with the automatic air brake: 0 for REL, 1 for LAP, 2 for SRV or 3 for EMG.
brakeNotchesLinear The highest value returned by brakeNotchesLinear.
● For trains without the automatic air brake and without hold brake, this is BrakeNotches+1.
● For trains without the automatic air brake but with hold brake, this is BrakeNotches+2.
● For trains with the automatic air brake, this returns 3.
locoBrake The current Loco Brake notch.
locoBrakeNotches The amount of Loco Brake notches the train has.
emergencyBrake Whether the emergency brake is currently active (1) or not (0).
hasAirBrake Whether the train has the automatic air brake (1) or not (0).
holdBrake Whether the hold brake is currently active (1) or not (0).
hasHoldBrake Whether the train has a hold brake (1) or not (0).
constSpeed Whether the const speed system is currently active (1) or not (0).
hasConstSpeed Whether the train has a const speed system (1) or not (0).
hasPlugin Whether the train uses a plugin (1) or not (0).
pluginState[i] The state of the ith plugin variable, returning an integer depending on the plugin. Is the same as atsi in the panel2.cfg.
FrontAxleCurveRadius[carIndex] Returns the curve radius at the front axle position of car carIndex.
RearAxleCurveRadius[carIndex] Returns the curve radius at the rear axle position of car carIndex.
CurveCant[carIndex] Returns the cant value for car carIndex.
Pitch[carIndex] Returns the pitch value for car carIndex.
Odometer Returns a signed number representing the distance in meters travelled by the current car.
Odometer[carIndex] Returns a signed number representing the distance in meters travelled by car carIndex.
Klaxon Returns the currently playing horn (if any) as follows: (0) No horns are playing (1) The primary horn is playing (2) The secondary horn is playing (3) The music horn is playing. Note If multiple horns are playing, the lowest value will be returned.
PrimaryKlaxon Returns 1 if the primary horn is currently playing, 0 otherwise.
SecondaryKlaxon Returns 1 if the secondary horn is currently playing, 0 otherwise.
MusicKlaxon Returns 1 if the music horn is currently playing, 0 otherwise.
passAlarm Whether the station pass alarm has been activated. Returns either 0 (inactive) or 1 (active).
stationAdjustAlarm Whether the station adjust alarm has been activated. Returns either 0 (inactive) or 1 (active).

If pluginState[i] is used with the built-in safety systems ATS and ATC, the following mappings for i apply:

i English 日本語 Return values pluginState[271] Meaning
256 ATS ATS 0 (unlit) or 1 (lit) 0 ATC not available
257 ATS RUN ATS 作動 0 (unlit), 1 (lit) or 2 (flashing) 1 0 km/h
258 ATS RUN ATS 作動 0 (unlit / non-flashing), 1 (lit / flashing) 2 15 km/h
259 P POWER P 電源 0 (unlit) or 1 (lit) 3 25 km/h
260 PTN APPROACH パターン接近 0 (unlit) or 1 (lit) 4 45 km/h
261 BRAKE RELEASE ブレーキ開放 0 (unlit) or 1 (lit) 5 55 km/h
262 BRAKE APPLY ブレーキ動作 0 (unlit) or 1 (lit) 6 65 km/h
263 ATS P ATS-P 0 (unlit) or 1 (lit) 7 75 km/h
264 FAILURE 故障 0 (unlit) or 1 (lit) 8 90 km/h
265 ATC ATC 0 (unlit) or 1 (lit) 9 100 km/h
266 ATC POWER ATC 電源 0 (unlit) or 1 (lit) 10 110 km/h
267 ATC SRV ATC 常用 0 (unlit) or 1 (lit) 11 120 km/h
268 ATC EMG ATC 非常 0 (unlit) or 1 (lit) 12 ATS is active
269 CONST SPEED 定速 0 (unlit) or 1 (lit)
270 EB EB 0 (unlit) or 1 (lit)
271 ATC speed indicator 0 - 12, see table on the right
● Sections (signalling)

The section context is defined when the object is placed using Track.SigF.

Variable Description
section The value of the section aspect currently shown.
If this variable is used outside of a Track.SigF context, the behavior is currently undefined and subject to change.

■ 6. Performance

There are certain kinds of animation which are less expensive, and others which are more. Also, the underlying object plays a significant role. If you want to design your animated objects with as best performance as possible for future releases of openBVE, take a look at the following performance table:

Animation Object Performance
State changes Has only opaque faces Good
State changes Has partially transparent faces Moderate
Translation Has only opaque faces Good
Translation Has partially transparent faces Moderate
Rotation Has only opaque faces Good
Rotation Has partially transparent faces Bad
Texture shifts Has only opaque faces Bad
Texture shifts Has partially transparent faces Bad

Performance is generally better if the result of a function only infrequently changes. So, even if you set the RefreshRate parameter to zero, performance is generally better if the outcome of your formula is constant over longer periods of time. On the other hand, if it changes every frame, performance is generally worse.

Generally, you should avoid using animation with partially transparent faces and stick to opaque faces when possible. Also, try to avoid texture shifts, and consider using state changes or translation where possible.

■ 7. Tips

■ 8. Example functions

● Blinking light
Template for a blinking light:

States = OBJECT0, OBJECT1
StateFunction = value == 0
RefreshRate = SECONDS

● Rotating wheel
Template for the code used in an exterior car object:

States = OBJECT
RotateXFunction = value + delta * speedometer / RADIUS_OF_THE_WHEEL

● Cycling through a list of objects
Template for objects that are to be cycled through:

States = OBJECT0, OBJECT1, OBJECT2, …
StateFunction = mod[value + 1, AMOUNT_OF_OBJECTS]
RefreshRate = TIME_PER_OBJECT

● Signal (3-aspect) for Track.Section(0; 2; 4)

States = RED_OBJECT, YELLOW_OBJECT, GREEN_OBJECT
StateFunction = section / 2

● Employing an approach-controlled delay in signals

If you want to create a signal that keeps being red until the train approaches it to some distance, then counts down a timer before it changes aspect to green, please refer to this post on the forum for a detailed explanation. Once you understand the concepts, you can use this code template:

Template for an approach-controlled delay in a signal with two aspects:

States = RED_OBJECT, GREEN_OBJECT
StateFunction = if[trackDistance>DISTANCE | section==0, 0, min[value + 0.5*delta/DELAY, 1]]

Template for an approach-controlled delay in a signal with any number of aspects:

States = RED_OBJECT, …, GREEN_OBJECT
StateFunction = if[trackDistance>DISTANCE | section==0, 0, if[value<0.5, value + 0.5*value/DELAY, section]]

■ 9. Formal Grammar

The formal grammar for the language may not match up perfectly with the implimentation included in OpenBVE. An example is a*-b which is valid under the grammar but the parser rejects it.

<expression>        ::= <xor_expression> “” <expression> | <xor_expression>
<xor_expression>    ::= <or_expression> “^” <xor_expression> | <or_expression>
<or_expression>     ::= <not_expression> “|” <or_expression> | <not_expression>

<not_expression>    ::= “!” <equal_expression> | <equal_expression>

<equal_expression>  ::= <plus_expression> “==” <equal_expression> | <plus_expression> “!=” <equal_expression> |
                        <plus_expression> “>”  <equal_expression> | <plus_expression> “<”  <equal_expression> |
                        <plus_expression> “<=” <equal_expression> | <plus_expression> “<=” <equal_expression> | <plus_expression>

<plus_expression>   ::= <times_expression> “+” <plus_expression>  | <times_expression> “-” <plus_expression>  | <times_expression>

<times_expression>  ::= <divide_expression> “*” <times_expression> | <divide_expression>
<divide_expression> ::= <minus_expression> “/” <divide_expression> | <minus_expression>

<minus_expression>  ::= “-” <function_call> | <function_call>
<function_call>     ::= <name> “[” <expression> (“,” <expression>)* “]” | <term>

<term>   ::= “(” <expression> “)” | <name> | <number>
<number> ::= <digit>*
<name>   ::= <letter> (<letter> | <digit>)*

<letter> ::= “A” | “B” | “C” | “D” | “E” | “F” | “G” | “H” | “I” | “J” | “K” | “L” | “M” |
             “N” | “O” | “P” | “Q” | “R” | “S” | “T” | “U” | “V” | “W” | “X” | “Y” | “Z” |
             “a” | “b” | “c” | “d” | “e” | “f” | “g” | “h” | “i” | “j” | “k” | “l” | “m” |
             “n” | “o” | “p” | “q” | “r” | “s” | “t” | “u” | “v” | “w” | “x” | “y” | “z”
<digit>  ::= “0” | “1” | “2” | “3” | “4” | “5” | “6” | “7” | “8” | “9”