Action A

Modify TTD's sprites.


Unlike actions 1 and 5, which add new sprites for new features or vehicles, action A modifies TTD's built-in sprites.


The data looks as follows:

Element	Size	Description
<Sprite-number>	dec	A sequential sprite number
<length>	dec	The total number of bytes used in this action
0A	B	Defines action 0A
<num-sets>	B	How many sets of sprites to replace
<num-sprites>	B	How many consecutive sprites in this set
<first-sprite>	W	Number of first sprite in this set

The set of <num-sprites> and <first-sprite> is repeated as often as <num-sets> specifies.

The following sprites will be RealSprites or RecolorSprites that replace the given TTD sprites. There must be as many of them as num-sprites of all sets added up.

Sprite-number

This is just the number you are at.

Length

Count the number of bytes in this action.

num-sets

This sets how many different sets of sprites to replace. Each set are a number of consecutive sprites.

num-sprites

How many consecutive sprites to replace in this particular set.

first-sprite

The first sprite number to replace in this set.


You can find the sprite numbers by looking in trg1.pcx, they're the little numbers above each sprite, except for the climate-specific sprites which are more complicated.

Unlike actions 1 and 5, the real sprites of action A do not count towards the sprite limit.

To replace sprites in other climates, you first need to find out what the sprite number is trg1.grf.
You set it to replace that number and add an Action7 which turns it off if it is not in the right climate.

One easy way to do this is to edit trg?[r].grf, use grfdiff (part of the grfcodec package) to create a grd, and then use grdtogrf to create a simple grf with the action A(s) written for you. The action7s still have to be added by hand.

You can as well use the online sprite id converter found on the same site.


Below is an example of what a real Action A pseudo-sprite could look like with the sprite entries under it.

Byte	Meaning
3	<sprite-number>
5	<length> of the action in bytes; start counting at 0A (<action>)
0A	<action>: sets this pseudo-sprite to function as action A
01	<num-sets>: sets it to 1 set to replace
0C	<num-sprites>: sets it to 12 sprites in this set.
3A 08	<first-sprite>: First Sprite of the set (3A 08 - Farms)