Train Director 3 - Scripts

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Image © Bahn TV

 

Version 3.6 of Train Director enhances the customization level of scenarios. In fact, it is now possible to associate scripts to almost every element present on a layout: signals, tracks, triggers and trains! By using scripts, it is possible to create complex conditions such as the creation of multiple itineraries, and to check the train's positions and movements, including the ability to create random delays.

The basic principle for using Train Director scripts is the execution of specific functions, activated when a particular event occurs. Each element on the layout reacts to different events. The script summary page lists all the events associated with each element type.

To explain the use of scripts you can refer to the following sample simulations included in the Train Director zip file:

  • trainscr.trk: example of scripts associated to trains. The simulation prints in the Alert window various messages when the state of the train changes (for example when the train enters the territory or when its direction is reversed).
  • signalscr.trk: example of scripts associated to signals. The simulation shows how it is possible to implement advance signals or protection signals conditioned to the entry path into a station.
  • trackscr.trk: example of a script associated to tracks and triggers.

How to associate Scripts to Elements

Each script is a portion of a text file associated to a layout element. Train Director allows the introduction of scripts associated to tracks directly from the track property dialog:

For trains, the scripts are embedded in the .sch file, together with the train's schedule. Here is an example of a script associated with a train:

Train: T3
Enter: 0:12, A
    0:14, -, S1
  Script:
    OnShunt:
       do showalert T3 shunting
    end
    OnReverse:
       do showalert T3 reversed
    end
  EndScript
.

For signals, scripts are separate text files, called "Train Director Scripts", or simply .tds files. These files can be associated to the various signals from the signal's properties dialog:

The reason for these differences is that for signals it's very common to re-use the same script for more than one signal (for example all advance signals will share the same script).

All scripts have a common syntax, composed of the name of an event, followed by one or more rows with conditions, expressions or commands. The events have the following structure:

OnXXXXX:
    # conditions, expressions, commands
    ....
end

where XXXXX specifies the event, and end specifies the end of the conditions, expressions or commands associated with the event.

Expressions are used to read or change properties of tracks, signals and trains. While the properties are specific of each element type, and are listed for each type in the scripts summary page, the elements themselves can be referred to in different ways:

  • by specifying the element's coordinate:  Track(x, y) specifies the track at coordinate x,y.
  • in relation with the train or signal or track affected by the event:   Track.property, Train.property, Signal.property.
  • in relation with the element that triggered the event:    .property.

For example, the ".aspect" property of a signal can be changed with the following expression:

    .aspect = red

Expressions are also used to specify conditions, by the use of comparison operators.

The following is an example of a conditional expression:

    Signal(10,23).aspect = red and Train(R2001).speed > 100 or Train(R2004).status = stopped

As you can see, different expressions can be linked by the operators "and" and "or".

The following is a list of conditional operators:

=     equal to
!      different from
>     greater than
>=   greater or equal to
<     less than
<=   less than or equal to

and   condition is true if both the left and the right conditions are true.
or      condition is true either the left condition or the right condition is true

In addition to layout elements, you can use the random operand in an expression to get a random value between 0 and 99 included, as in the following example:

    random < 40

In this case, the condition is true (on average) 40% of the times.

Another operand that can be used in expressions is time, to refer to the "simulator clock". For example:

    time > 1430

The value of the time operand is expressed in hhmm, that is hours+minutes; in the example, the condition is true after 14:30 hours. There is no provision for AM/PM notation.

In addition to expressions to change the properties of an element, scripts allow the use of 2 types of commands:

  • condition commands
  • imperative commands

Condition commands have the following structure:

    if expression
       command1
       command2
       ...
    else
       command3
       command4
       ...
    end

The if command checks if the expression is true, and if it is, it executes the command sequence 1, 2, etc., while ignoring the command sequence 3, 4, etc.
If the expression is not true, the if command ignores the command sequence 1, 2 etc. and executes the command sequence 3, 4 etc. instead.

Note that the else part is optional, and it can be omitted if there are no commands to execute if the condition is not true.

Also note that an if command can contain other if commands, so that one can specify more conditions that will be checked only after the outer if has been checked.

Imperative commands are introduced by the word do, and allow to change the behavior of the simulator, in the same way as what happens for triggers.

The available commands are:

do stationsched shows the station schedule
do fast increases the simulation speed
do slow decreases the simulation speed
do shunt train starts shunting the specified train
do traininfopage train shows the specified train schedule in an HTML page
do traininfo train shows the specified train's schedule in a dialog
do decelerate value train reduces the speed of the specified train by the specified value (in km/h)
do accelerate value train increases the speed of the specified train by the specified value (in km/h)
do reverse train reverses the specified train's direction
do click x, y simulates a left mouse button click on the specified coordinates
do rclick x, y simulates a right mouse button click on the specified coordinates
do ctrlclick x, y simulates a left mouse button click with the Ctrl key pressed on the specified coordinates
do itinerary name activates the specified itinerary. It is not necessary to have a button on the layout associated to the itinerary
do assign oldtrain newtrain assigns the rolling stock of "oldtrain" (which must have been arrived to its final destination) to "newtrain"
do play soundfile plays the specified sound file
do skip advances the simulator's clock to 3 minutes before the next event (useful to avoid waiting several minutes when there are no trains on the layout) All trains must be stopped or arrived or exited for this command to be allowed
do split train length splits the specified train in two pieces, and shunts the front piece to the next station
do script file executes the OnEnter: action in the script contained in the specified file
do showinfo file.htm shows the content of the specified HTML page in the "Scenario Info" window
do showalert text shows the specified text string in the alert window
do clearalert clears the alert window
 

An additional imperative command stops executing a command sequence and returns to the simulation. It is specified by the word return, as in:

    if .aspect = red
       return
    end

All commands after the return line will be ignored.

In the next page we describe in detail the scripts that can be associated with signals. Also look at the various scenarios available from the scenario directory page, for more examples on how to use Train Director scripts.