[Freeciv-Dev] Re: Tidying savegames to pave the way for plug mapgens

[Raimar Falke <rf13@xxxxxxxxxxxxxxxxx>]

On Wed, Apr 23, 2003 at 09:15:24PM -0400, Cameron Morland wrote:
> Hi,
> 
> This patch does a number of things, primarily to make plug-in map
> generators much easier to write. For the most part I've been changing
> what is required to successfully load a file as a savegame.
> 
> While I was at it I removed some features required to load extremely
> old savegames. We already require that a savegame claim to be version
> 1.9.0 or later, so checking for features from 1.1 (!) isn't
> productive.
> 
> Irrelevant Parameters
> =====================
> First of all, there are a very large number of parameters in a
> savegame file, many of which do not need to be stored in the game,
> especially for scenarios. It should be possible to set parameters,
> such as gold, skill_level, nplayers, settlers, explorers, save_nturns,
> etc and then load a scenario, without the scenario overriding the
> specified values.
> 
> Most `x = secfile_lookup_<type>(...)` statements have been replaced
> with `x = secfile_lookup_<type>_default(..., x)`, ie use the value
> which the person running the server has already specified (or the
> default, if the user hasn't specified anything). Most options just
> need to be recorded in the file if the file wishes to change 
> the pre-existing value. For more complex options, such as
> fixed_start_positions and heightmaps (see below), I use the
> has_capability thing, so the savegame must specify that it will use
> those features. 
> 
> The only parameters that a scenario must specify are map.width,
> map.height, game.version >= 10900, and game.server_state == 0.
> If a scenario wants to keep its tinyisles, it has to specify
> tinyisles=1; mapgen makes much more sense this way.

The idea is good.

> Loading Height Maps
> ===================
> Currently, generators{1,5} construct a height map, then run make_land to
> add the terrains. Generators{2,3,4} make tilemaps directly, including
> rivers. I wanted external generators to be able to make use of the
> terrain/river/specials placing algorithms (especially since Karen and
> Ross have been working on making them better), so they needed to be
> able to provide height maps.
> 
> With this patch, a map can provide a height map, which is a 16-bit
> hexadecimal map. Once this is loaded the built-in terrain placing
> algorithm runs (with specified landmass, etc), and a tilemap is
> created.

This looks like an intermediate step. This depends on what the goal
should be. If we have the infrastructure we should IMHO out-source ;)
all of the map generators. There could than be a generate_height_map
program which is used by the real map generators programs. But all
this doesn't matter for the core freeciv code. It just gets a
(terrain-)map. If this is also our goal than this above patch step
isn't necessary.

> General mapgen layout
> =====================
> A few bits of mapgen make more sense now (IMHO). Instead of requiring
> each generator to do everything, it can specify what it does by
> setting booleans, then default functions can be applied later. This
> should make the code tidier. 
> 
> Since making rivers depends on having a height map, I wrote a simple
> function to generate a heightmap given a tilemap.

Also this logic should be moved to the external program.

> Load Command
> ============
> If you ask for help on the 'load' command, it will say that "Any
> current data including players, rulesets and server options are lost."
> This is rather annoying, and is mostly fixed by the "irrelevant
> parameters" section above. It still screws up the players, but pretty
> well everything else should be left alone (assuming, of course, that
> the file you load doesn't specify these things). It's a start.
> 
> External Generators
> ===================
> I haven't written the glue code to run external map generators, I've
> just been running them from the command line, redirecting to a file,
> then loading the file. But now at least the plug-in generators don't
> have to be so complicated; if they want to use a heightmap technique,
> they can just generate the heightmap and let mapgen do the rest.

> Attached are the diff, and a pretty terrible map generator written in
> Perl (it's not a great generator, it's just something I hacked
> together as an example). Comments? I'll be away for a few days, but
> I'd like to see what people think.

> ? generatesillymap.pl
> ? punchmap.pl

The perl code isn't included.

        Raimar

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