Vehicles

Vehicle variables

Variables without parameter

Variables that require an argument

Callbacks for vehicles

In order to set properties for vehicles via callback VEH_CB_VEHICLE_PROPERTIES it's necessary to query the general variable extra_callback_info1 which can take different values depending upon the vehicle type:

Where for the properties available for all vehicle types XXX can either be TRAINS, ROADVEHS, SHIPS or AIRCRAFT. Note also that the return values don't yet support units, you'll need to enter the properties untranslated (e.g. road vehicle weights are in quantities of 0.25 tons).

The following code is an example for the use of callbacks and most notably also the creation of articulated vehicles which can only be created by means of the VEH_CB_ARTICULATED_PARTS:

/* Here would have to be definition of sprite sets and groups */

/* callback for articulated vehicles: 4 wagons with special sprites for first and last */
switch(FEAT_TRAINS, SELF, rail_engine_articulated_parts, extra_callback_info1) {
    1..2: return rail_wagon; // middle parts use rail wagons
	3: return rail_engine;   // last part is this rail engine again
    CB_FAILED;               // no more than 4 vehicles
}

/* Set the (empty) weight of the vehicle depending on the cargo it carries */
switch (FEAT_TRAINS, SELF, rail_wagon_cb_property_weight_switch, cargo_type_in_veh) {
    PASS: return 30; // Passenger wagons are heavier
    TOUR: return 30; // Tourists are also passengers
    CB_FAILED;       // use value set in the property block for other cargos
}

/* Set (conditionally) different properties of the train */
switch (FEAT_TRAINS, SELF, rail_engine_cb_property_switch, extra_callback_info1) {
    PROP_TRAINS_WEIGHT          : rail_engine_cb_property_weight_switch;
    PROP_TRAINS_CARGO_CAPACITY  : rail_engine_cb_capacity_switch; // not shown here
    CB_FAILED;                                                    // we don't set other properties
}

/* Check for each (active) callback */
switch (FEAT_TRAINS, SELF, rail_engine_switch, current_callback) {
    VEH_CB_REFITTED_CAPACITY:  rail_engine_cb_capacity_switch; // switch not shown here
    VEH_CB_VEHICLE_PROPERTIES: rail_engine_cb_property_switch;
    VEH_CB_ARTICULATED_PARTS: rail_engine_articulated_parts;
    rail_engine_graphics_switch; // go to graphics branch, if no callback asked for; not shown here
}

/* Define this rail engine */
item(FEAT_TRAINS, rail_engine) {
    property {
        callback_flags:                 bitmask(VEH_CBF_ARTICULATED_PARTS, VEH_CBF_REFITTED_CAPACITY); // activate callbacks
        cargo_capacity:                 20;
        weight:                         24 ton;
    }
    graphics {
        rail_engine_switch;
    }
}

Properties common to all vehicle types

To determine whether your vehicle can be refitted to a certain cargo, OpenTTD uses the following table:

You should use refittable_cargo_classes and non_refittable_cargo_classes to decide to which cargos your vehicle is refittable, and only use refittable_cargo_types as a last resort to include/exclude some cargo type.

Note that the default cargo cannot be selected explicitly. Instead it is automatically set to use the first refittable cargo, whenever one of the refitting properties is set.

Train properties

Road vehicle properties

Ship properties

Plane properties