[docs] Started writing MWM.md

docs/MWM.md

@@ -1,11 +1,115 @@
 # MWM Files
 
+MAPS.ME uses maps in its own vector format, MWM. It contains classified features sorted and simplified by zoom level.
+For car routing, it needs a separate routing index in a `.mwm.routing` file. We build maps for the entire planet:
+
+* [daily.mapswithme.com/direct/latest](http://direct.mapswithme.com/direct/latest/) - official maps bundled with releases.
+
 ## Building
 
-### Single region
+For building maps, you need compiled Generator Tool and, for routing indices, OSRM backend.
+See [INSTALL.md](INSTALL.md) for compilation instructions. We usually use this line:
 
-### Part of a planet
+    CONFIG=gtool omim/tools/unix/build_omim.sh -cro
+
+Scripts described here require OSM C Tools, which are maintained as a submodule of the omim repository.
+
+### A Single Region
+
+Having built a generator tool, prepare a source file in pbf/o5m/bz2 format, and run:
+
+    omim/tools/unix/generate_mwm.sh source.pbf
+
+In some minutes it will create a similarly-named `.mwm` file in the same directory as the original file.
+Specify `TARGET` variable for changing that (e.g. `TARGET=.`). The script runs `generator_tool` twice,
+see `find_generator_tool.sh` script for an algorithm on how it finds it. All temporary files are created
+with `mktemp` and then removed.
+
+The resulting file won't have any coastlines, though MAPS.ME will overlay zoomed-in map with a low-quality
+generalized coastline. To add a detailed coastline, you would need a `WorldCoasts.geom` file and
+a [border polygon](http://wiki.openstreetmap.org/wiki/Osmosis/Polygon_Filter_File_Format) for a source
+file area. Having that, run (and prepare to wait a bit longer):
+
+    COASTS=WorldCoasts.geom BORDER=source.poly omim/tools/unix/generate_mwm.sh source.pbf
+
+A car routing index will be built when you specify a second parameter: either a full path to a Lua script
+with a routing profile, or any gibberish, in which case a default `car.lua` from omim repository
+would be used. For example:
+
+    omim/tools/unix/generate_mwm.sh source.pbf asdf
+
+Inter-mwm navigation requires another index inside a `.mwm.routing` file. To build it, you would need
+border polygons for not only the source region, but all regions neighbouring it. The source border polygon
+must have the same name as the source file (e.g. `Armenia.poly` for `Armenia.pbf`), and in the target
+directory shouldn't be a `borders` subdirectory. With all that, just use this line:
+
+    BORDERS_PATH=/path/to/polygons omim/tools/unix/generate_mwm.sh source.pbf asd
+
+### The Planet
+
+To create a bunch of MWM files for the entire planet, splitting it by border polygons, we have
+a different script, `generate_planet.sh`. It will print a short help when run without arguments.
+The usual line we use is:
+
+    TARGET=/opt/mwm/151231 omim/tools/unix/generate_planet.sh -a
+
+This is a shortcut for following options:
+
+* `-u` - update a planet file from osm.org (use `-U` when you need to download one, specify `PLANET`
+variable if it's not in `$HOME/planet/planet-latest.o5m`).
+* `-l` - filter and process coastlines, creating `WorldCoasts.geom` and `.rawgeom` files.
+* `-w` - generate overview maps, `World.mwm` and `WorldCoasts.mwm`.
+* `-r` - generate routing indices, `.mwm.routing` file for each `.mwm`.
+
+All border polygons from `BORDERS_PATH` are processed into MWM files by default. You can
+specify only required polygons in `REGIONS` variable, or set it to empty value, so no regular
+MWM files are created. The whole process takes 15 hours on a 40-core server, so we suggest
+you specify your e-mail address in a `MAIL` variable and get a mail when the generation
+is finished.
+
+If a previous run ended with an error, the next one will ignore arguments and continue with
+the same arguments as the previous time. Set `-c` option to ignore the stored status.
+
+Log files for each region and the entire process (`generate_planet.log`) are written to
+`logs` subdirectory of the target. Intermediate data requires around 250 MB of space, and
+to clean it during the process, specify `KEEP_INTDIR=` empty variable.
+
+#### Steps
+
+The planet generation process is divided in several steps, which are printed during the
+script run, along with timestamps. To start generation from a specific step, specify it
+in the `MODE` variable (and make sure you don't have stored status, or run with `-c`
+option).
+
+* Step 1 (`coast`): updating planet file.
+* Step 2: filtering and processing coast lines. If there was a merge error, the script
+prints way identifiers, waits 40 minutes and tries again from step 1.
+* Step R: preparing `.osrm` files for routing indices. PBF files for each region are
+cut out of the planet, then OSRM backend scripts process each of these. Can work
+asynchronously if `ASYNC_PBF=1` variable is set.
+* Step 3 (`inter`): generating intermediate data for the planet.
+* Step 4 (`features`): generating features for each region, splitting the planet.
+* Step 5 (`mwm`): building the resulting MWMs.
+* Step 6 (`routing`): building `.mwm.routing` files out of MWMs and `.osrm` files.
+* Step 7 (`resources`): updating resource and map lists.
+* Step 8 (`test`): calling `test_planet.sh` to run routing tests.
+
+### Variables
+
+*todo*
 
 ### Testing
 
+To test that the generator is not broken, you don't have to wait for 20 hours processing
+the whole planet: instead download [a 150 MB extract](http://osmz.ru/mwm/islands/) with
+some islands and the corresponding script `islands.sh` and put these into `omim/tools/unix`.
+Run the script with options for `generate_planet`, e.g.
+
+    omim/tools/unix/islands.sh -lwr
+
+In a half an hour you'll get files for 4 regions in a `target` subdirectory. Note that
+you can build both generator tool and OSRM backend with the `build_omim.sh` script.
+
 ## Format
+
+*todo*