Question about Action-A

[mikeel]

hi to all
i'm trying to understand how grfs work, but i have a problem.
in action-a, according to the manual, the last two values represent the first-sprite:

Code: Select all

<first-sprite>	W	Number of first sprite in this set

but where i can find this number?
(for example if i want replace a building)
thanks
mikeel

[mph]

i think this is what you mean-
you decode trg1r.grf - that is the main graphics file for most of the graphics in the game-
you then get trg1r.nfo and trg1r.pcx
open the pcx file - and there will be lots of sprites- each with a number above them- and that is the sprite number.
a set of sprites is a set of consecutive sprites- if you want to replace a certain building- find the sprite or set of sprites in the pcx file, and the first sprite number is what you want.

i hope i understood correctly- i too am only learning-

[mikeel]

well i don't think that is the little number above the sprites becouse it is a decimal value.
the action-A requires instead two hex values:
in the example of the manual

3 * 5 0A 01 0C 3A 08
where
3A 08 <first-sprite>: First Sprite of the set (3A 08 - Farms)

but in the pcx file the first sprite of the farm is 2108

[mph]

yes- the little number above the sprite is a decimal number.

the action a reqires this number in hexidecimal in little endian format i believe.

in the wiki-on the actionA page- it says in the table that the element- <first-sprite>, which is the number of the first sprite in the set, has size w.
size w means that

This parameter is a two-byte word, specified in little-endian byte order

from this page- http://wiki.ttdpatch.net/tiki-index.php ... nsDetailed

so you take the decimal sprite number from the trg1r.pcx file and convert this do hexidecimal. the windows calculator can do this.
taking an example i have done- to replace the fences on the railway tracks.
first sprite number is 1301 in decimal

convert to hexidecimal - giving 515.
make this a two byte word- 05 15
put in little endian- 15 05

and that is what you use in the actionA


i hope this is what you mean. and that im explaining it ok!

edit- you may be confused- the first sprite for the farm is 2106 not 2108. which in hexidecimal put in little endian is 3A 08

[mikeel]

I was getting crazy becouse i didn't realize that i have to switch the two values in little endian ... thanks

[minime]

Why not just save yourself the trouble and use those handy little escape sequences? Then you can just write the decimal number and not have to worry about endianness.

[mikeel]

i haven't understand... what are the "little escape sequences"?

[minime]

Read the documentation - in particular the part of section "Byte Order" that begins with

In Info version 7 and later (supported by grfcodec version 0.9.9 and later), grfcodec can do some of this work for you...