Difference between revisions of "NMLTutorial"

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Revision as of 11:18, 22 August 2011


Since june 2010 a new coding language for creating TTDpatch/OpenTTD GRF's exists: Newgrf Meta Language or NML. It differs significantly from the old way of GRF editing and although documentation is available it may still be a challenge for people interested in using NML code. After all NML is still a form of programming language and not a GUI-based editor.

There will be detailed examples of how coding in NML works on this new TT-wiki. Make sure to check the progress of this NML tutorial regularly.



NML is a high-level NewGRF language compiler which compiles NML and LNG files into newgrf files (and NFO files, if asked to do so). Coding a NewGRF in NML is similar to writing in any other programming language except that there are no real sub-routines; you can use the usual definition and condition statements.

Language support

NML provides easy support for different languages in one GRF. This is achieved by creating language files (LNG). These language files follow the convention used for OpenTTD translation files. When compiling NML files a search for language files will automatically be performed. Even without providing additional translations at least one language file must be specified, called default.lng.

Image format support

One of the conveniences of NML is the possibility to read other image formats, most notably PNG. Remember though that those images still need to supply the proper 8bpp palette and are supported by the python image library.


Does the above sound impressive, maybe even threatening to you? One illustration often says more than a thousand words so let's show the difference with two illustrations:

NFO code snippet

// Automatically generated by GRFCODEC. Do not modify!
// (Info version 7)
// Escapes: 2+ = 71 = D= = DR 2- = 70 = D+ = DF 2< = 7= = D- = DC 2> = 7! = Du* = DM 2u< = 7< = D* = DnF 2u> = 7> = Du<< = DnC
2/ = 7G = D<< = DO 2% = 7g = D& 2u/ = 7gG = D| 2u% = 7GG = Du/ 2* = 7gg = D/ 2& = 7c = Du% 2| = 7C = D% 2^ 2sto = 2s 2rst = 2r 2+ 2ror = 2rot
// Format: spritenum pcxfile xpos ypos compression ysize xsize xrel yrel
0 * 4 \d416
1 * 92 08 07 "SER0" "ÞSwedish Rails nightly-r52M" 00 "ÞSwedish rails are a replacement for the default rails" 00

NML code snippet

grf {
grfid : "SER0";
name : string(STR_GRF_NAME);
desc : string(STR_GRF_DESCRIPTION);

NML language file snippet

##grflangid 0x01
STR_GRF_NAME  :Swedish Rails {VERSION}
STR_GRF_DESCRIPTION  :Swedish rails are a replacement for the default rails