Action0
Introduction
Defining new graphics feature properties
Action 0 allows to change the feature properties of 'features', i.e. vehicles, stations, bridges, houses and more.
Syntax
The data for Action 0 looks as follows:
<Sprite-number> * <Length> 00 <Feature> <Num-props> <Num-info> <Id> (<Property <New-info>)...
Here is a short overview of what every term means:
| Element | Size | Description |
|---|---|---|
| <Sprite-number> | dec | A sequential sprite number |
| <Length> | dec | The total number of bytes in the action |
| 00 | B | Action type. In this case, 00 |
| <Feature> | B | Which type of feature you would like to change |
| <Num-props> | B | How many properties you would like to change per vehicle or station |
| <Num-info> | B | How many vehicles/stations you would like to change |
| <Id> | B* | The ID of the first vehicle/station to change |
| <Property> | B | What property to change for each vehicle/station |
| <New-info> | V | The new value of the property |
You can put an Action 0 anywhere after Action 8 in the GRF file.
The <Id> is an extended byte since 2.0.1 alpha 61, to support the definition of >255 sound effects. In OpenTTD since r13482, extended IDs (up to 65535) can be used for vehicles as well. However there is currently a caveat that articulated parts must be below 128.
Descriptions
Sprite-number
Action 0 can appear anywhere in the GRF file, so set it to the sprite number you are currently at.
Length
The total number of bytes in Action 0. Start counting from <Action>, the bit that sets the pseudo-sprite to act as the specified action.
Action
The type of action this pseudo-sprites defines. It should be 00 here because we want this pseudo-sprite to act as Action 0.
Feature
This sets the type of feature that you wish to change. Set it to:
| Value | Feature |
|---|---|
| 00 | trains |
| 01 | road vehicles |
| 02 | ships |
| 03 | planes |
| 04 | stations |
| 05 | canals |
| 06 | bridges |
| 07 | houses (see defaults) |
| 08 | global variables |
| 09 | industry tiles (see defaults) |
| 0A | industries (see defaults) |
| 0B | cargos (see defaults) |
| 0C | sound effects |
| 0D | airports |
| 0E | signals (Action 0 is not valid for this feature) |
| 0F | newobjects |
| 10 | rail types (OpenTTD r18969) |
| 11 | airport tiles (OpenTTD r19204) |
Note that the above list is the master list for all actions where not stated otherwise.
Num-props
This is the number of properties that you wish to change per vehicle or station. Note: even if you wish to set the same properties to the same value for different vehicles then you must still repeat the properties and their values for each vehicle.
Num-info
Simply the number of vehicles that you will change using this action 0.
Id
The Vehicle ID of the first vehicle or station to change. If num-info is greater than one, this vehicle/station and the following vehicles/stations will be changed.
Property
The number of the property that will be changed. This and the New-info section are repeated as many times as there are properties to set; in total, there are < num-props> property bytes.
See relevant sub-section (links at the bottom) for more details.
New-info
The new information that will replace the previous information for the specified property. This is a variable size; dependent upon the property. Each property byte is followed by <num-info> new-info sections. The appropriate \b, \w, and \d escape sequences can be quite useful for most < new-info>s. See the discussion of escape sequences for further information.
Features and properties
Each feature has its own very specific properties. These are explained in detail in their separate pages.
You will also find the minimum GRF version (in Action 8) that supports this property, or alternatively if the property was introduced between version changes, the patch version number that you can check with Action 7.
