The terrain as seen in game are wrp files (world maps). The 'map' generally consist of an 'island', surrounded by sea texture. All official maps are square areas 256 x 256 'cells'. Each 'cell' defines attributes of that part of the map in a fixed 50 meter square grid. Thus a 256 square map covers 12.8km square.
With the introduction of Resistance, the map sizes could be considerably larger. No official BI island took advantage of this. However, the OFP Community has, for example: BAS Tonal, PMC Rugen 25km, PMC Rattler 25km, to name only a few.
A wrp file contain indexed references to models (p3d files) and textures (pac/paa). A wrp file does not contain the models, or the textures. Instead, these models and textures are held inside a mixture of one or more pbo files. Frequently, since this is after all an island, the very same p3d models accessed in this wrp file, this island, might also be available as separate Mission Editor models. Buildings eg, grass eg, trees, eg.
The model and texture pbo files can be 'official' (eg O.pbo,data3d.pbo), or unofficial. Any and all pbos that contain pxx files can be referenced by the wrp file. The wrp file itself, may, or may not be, inside one of the very same pbo's that contain some of the pictures, but, that, is immaterial to the wrp.
A wrp file is accompanied with a familiar config.cpp, or it's raPified equivalent, config.bin.
All references to models and textures within the config begin:
filename_of_pbo\thing.pxx note there is NO leading slash.
pxx of course are p3d. pac. or paa extensions. Depending on context, one or other of these file externsions are default. But, for modellers to play safe it is better to be specific.
There are two file formats in use. Either can be used in the engine.
This is Bis's 'internal', or 'official' format for all wrp files (islands) in the game. It is in a packed binary representation to conserve space.
There are two versions OPRW files
OPRW2: Non Resistance format. (Abel,Eden,Cain,Intro,trinity)
OPRW3: Resistance format. (Nogova, PMC Rugen eg)
was introduced for the Island of Nogova. There are minimal differences between the two formats (similar in triviality to pbo files in general) The tool to manipulate OPRW files directly is WrpEdit. This was an early tool in the life of the OFP community supplied by the now defunct ofpinternals. This tool worked with these maps by reverse engineering details from zwadar. It only works on non resistance file format (version 2). Changing a resistance format to non resistance is trivial and detailed elsewhere.
OPRW17 / OPRW18
ArmA OPRW format. Intro (Rahmadi) and Sara (Sahrani) is v18 and SaraLite (demo) is v17.
The mapSize values are different. First pair = texture grid, second pair = terrain grid.
This is the unpacked version. The tool for 4WVR is WrpTool. This format is much larger in size than OPRW as its not optimized, however ingame there is no difference.