As of Liquid War 5, most levels have been contributed by players. While the maintainer of Liquid War 6 has technical knowledge to develop the game, artistic talent and taste might not be his domain of excellence 8-)
Therefore contribution are truely welcomed when they take the form of a new, original, fun and good looking level. It's believed the levels often make the game much more than its engine. This is true for any type of game, and Liquid War is no exception.
So this section is here to help players understand how to hack existing levels, and create new ones, in the hope that 1) they can enjoy their own creations and 2) possibly share their work with others.
Note that this manual might refer to levels and maps: they are just two different names to describe the very same thing. It's an alias.
Liquid War 6 stores level information in a plain directory.
There is no such thing as an opaque .dat
binary file.
The name of the level is the name of the directory itself,
and its elements are the files contained in it.
Files must follow a precise naming scheme. For instance
Liquid War 6 expects a map.png
file to be present
in each map directory.
All image files in a level use the
Portable Network Graphics
or JPEG format.
It is possible that in the long term, Liquid War 6 will
be able to handle levels as .tar.gz
or .zip
files. In that case these files will only be a compressed
image of the actual level directory.
See the ./map/
directory of the source Liquid War 6
distribution to see example of maps.
This is the only required file in a level.
In fact, the existence of map.png
makes a
directory a level. When checking wether a directory
is a correct level, Liquid War 6 simply tests the
existence and validity of map.png
.
This image is a simple black & white area, where white zones are the background, the sea, the places where fighters can move, and black zones are the foreground, the walls, the places where fighters can't go.
This informations can be stored in a 2-color indexed file, or in a grayscaled or even truecolor RGB file, but color information won't be used. Internally, Liquid War 6 will read the color of every point. If it is over 127 on a 0 to 255 scale, it will be considered as background, if it is below 127, it will be considered as foreground.
Liquid War 6 can handle mutiple layer maps. Think of a pile of maps, one being on top of the other. This allows you to create a volume, the game considers every layer has two axis x and y, and the z axis is to travel through layers. First layer corresponds to z=0, second layer to z=1, and so on.
Here are the files you can use to define layers:
map.png
this one is on top, it's always defined (z=0)
layer2.png
(z=1)
layer3.png
(z=2)
layer4.png
(z=3)
layer5.png
(z=4)
layer6.png
(z=5)
layer7.png
(z=6)
A layerX.png
file should be designed exactly like map.png
.
In fact, map.png
could simply have been called layer1.png
.
Up to 6 extra layers can be defined
(from layer2.png
to layer7.png
).
This is a hardcoded limit.
It allows you to define 7 different layers, including
the top map.png
layer.
Keep in mind this layer system is not real 3D,
it's more a “2D and a half”
model. Adding layers can considerably slow down the game, so it's
wise to try and use as few layers as possible. Technically, 3 layers
will allow you to build bridges and tunnels, which is probably
the most usefull construction using layers. Fighters can also
have difficulties navigating through layers so piling up layers
in narrow “vertical” z-axis based tunnels is probably not a
great idea.
The ufoot/concept/pass
map of the liquidwar6-extra-maps
demonstrates basic layer usage.
It is possible to define a texture for the map by
putting a texture.png
or texture.jpeg
file.
It does not need to have the
same dimensions as the map itself. Indeed, textures can
be much more precise than the actual logical map.
There's no theorical limit on how big a texture can be, more precisely, it can be much bigger than any hardware/driver maximum texture size. In practice, a too big texture will waste your video card RAM, and slow everything down. Sizes ranging from 640x480 to 1600x1200 are reasonable texture sizes.
If you don't define this, the map.png
file will
be used as the texture, and also import colors from
style.xml
if defined.
Note that the shape of the texture defines the shape of the map, that is, the ratio with which it will appear on the screen.
The PNG alpha layer will be used for transparency.
But to save disk space, it can be convienient to prefer the JPEG
format, use texture.jpeg
instead of texture.png
and store the alpha layer in a separated file,
called texture-alpha.jpeg
. This avoids handling heavy
PNG files, PNG compression not being performant on most textures.
In texture-alpha.jpeg
, black is considered opaque,
and white is transparent. Different levels of gray correspond to
different levels of opacity. Previous versions of the game
used the other way of doing things (black is transparent) because
this is technically, the most obvious way to do things. Black is 0
and transparent is 0. But for a human “reader” of the map
this does not make sense. One generally expects white to be the
equivalent of “undrawn” or “blank”, well, if it's undecided,
void, transparent, whatever, it's white. When the Gimp
flattens an image, it becomes white, not black.
So white is transparent. Period.
If there's a glue.png
or boost.png
file in the map directory
(you can use one of them or both) then they will be interpreted as follow:
glue.png
and boost.png
are white, nothing special
happens, fighters follow their default behavior
glue.png
is black, fighters will be slowed down. How
slowish they will be depends on the 'glue-power' parameter. If 'glue-power' is
3 then fighters will move three times slower.
boost.png
is black, fighters will behave faster. How
fast they will be depends on the 'boost-power' parameter. If 'boost-power' is
2 then fighters will move two times faster.
glue.png
or boost.png
are gray, they will
be slowed down less or speeded up less depending on how dark the grey is.
There can be, at the same place, some gray or black in both boost.png
and glue.png
. How this will behave exactly is not really clear at this
stage, the recommendation is not to do this (it does not really make sense
anyway) but if you do it, game won't complain.
It's also wise not to abuse of boost.png
for obviously, a map
filled with “boosted” zones at a X10 pace will require much more CPU
than the same map with no such setting. This might fool the automatic
resampling algorithm and lead to maps that are unplayable. The spirit of
boost.png
is just to make a few spots go faster.
It's also important to note that behaving faster or slower means moving faster or slower but also attacking faster or slower, and, in a general manner doing any action with a different pace.
If there's a danger.png
or medicine.png
file in the map directory
(you can use one of them or both) then they will be interpreted as follow:
danger.png
and medicine.png
are white, nothing special
happens, fighters follow their default behavior
danger.png
is black, fighters die automatically, that is,
they become black and loose health. How dangerous these zones are depends
on the 'danger-power' parameter.
medicine.png
is black, fighters regenerate faster, they
become bright and shiny as if auto-healing. How efficient this medicine is
depends on the 'medicine-power' parameter.
danger.png
or medicine.png
are gray, well,
it's in between, the “danger” and “medicine” effect will be proportional
to the level of gray.
There can be, at the same place, some gray or black in both medicine.png
and danger.png
. How this will behave exactly is not really clear at this
stage, the recommendation is not to do this (it does not really make sense
anyway) but if you do it, game won't complain.
The four files:
one-way-north.png
(AKA “up”)
one-way-east.png
(AKA “right”)
one-way-south.png
(AKA “down”)
one-way-west.png
(AKA “left”)
can be used to force the fighters to go in one given direction, on some parts of
the map. If an area is black on one of this meta-layers, then fighters will go
in the given direction. For instance, a black zone in one-way-north
will
make fighters go to the north (AKA “up” direction) regardless of the cursor
position. The fact that this is a one-way path is understood by fighters and they
will take this in account when choosing the shortest path to go somewhere.
You can combine vertical and horizontal one-way informations, making diagonal
one-way paths.
Whereas style.xml
is only about the appearance
of the map, rules.xml
allows the map designer
to change pretty much any parameter.
Ultimately, the player can still ignore these settings and overide them with its own values, but the idea is: most game options are only pertinent in a given context. For instance, on some maps it's interesting to move slowly, on some other it's interesting to move fast. Some maps might be playable packed with fighters everywhere, some other might be much more fun with almost nobody on them.
The approach in Liquid War 5 was to make the options available, but let the player himself find the right settings for the right map. The consequence is that no one ever used all those cryptic options in the advanced options menu, and probably 99% of the players ended up playing with default settings. This is not that bad, but given the fact that changing a few parameters one can totally transform the gameplay, it has decided been that in Liquid War 6, the map designer suggests the right options that matches his map.
This does not prevent the player from toying with options himself, he can still do it.
There's also one important point to note: all these options are
technically implemented as integer parameters. We certainly do not
want any float here, since, and it is a Liquid War specific behavior,
the game must be 100,00% predictable and behave the same on every platform.
As there is nothing like exactness when speaking of floats, those are
forbidden here. As for strings, we are dealing here with low-level
internals, and this section is not about telling a story. They
are technical options only. Booleans are implemented with the usual
false = 0
and true = 1
convention. Note that other
config files in Liquid War 6 might rely on floats, strings, and
booleans with conventionnal true
and false
values,
but not this one. rules.xml
is special.
This rules.xml
file is a direct image of the internal
“rules” structure, so it contains technical, sometimes not very
user-friendly parameters. While hacking rules.xml
directly
is a good way to test things, most of the time, the other file
hints.xml
contains more high-level informations that do
the job the right way. A typicall example is speed.
See rules.xml reference.
This parameter is only used by the map loader. The map itself contains none of these parameters, they are only clues (hints, in fact..) on “how to load the map” which are passed to the loader.
Let's take an example : speed. This rules.xml
file has
a (rather) easy to use “speed” parameter, which will do all the job
of finding the right resolution for your map, the right “rounds-per-sec”
and “moves-per-round” parameters, in short, it will set many
other parameters to fit your needs.
As far as the map designer is concerned, rules.xml
and hints.xml
could have been merged (but so would have style.xml
) but internally
they are very different: rules.xml
contains the real parameters,
the one used by the algorithm whereas hints.xml
contains only instructions
which are used once when loading the map and then disappear. The core algorithm
has no idea of what was in hints.xml
, once it's loaded.
See hints.xml reference.
This is a simple XML file defining various appearance parameters. It has absolutely no effect on gameplay. These settings can ultimately be overriden by the player, but the idea is that if the map designer thinks this level looks better with this or that option, let him say it in this file.
See style.xml reference.
This is a very important point. Liquid War almost *always* resamples maps, unless you ask it not to do it. This is not recommended, it is believed in the general case, letting the internal algorithm make its own decisions is better than trying to figure out oneself “which is the best resolution”.
The reason is, the right resolution (we're talking here of the logical resolution, how many fighters wide is the battlefield) often depends on the speed and general ressources the of the computer the program is running on. The map designer does not have this information. The program does. It runs a bench at startup. So this way it can choose, at runtime, the resolution which fits best.
The recommended way of doing things is not to try to be too picky about
rules.xml
parameters related to speed and also let the default
map size limits in hints.xml
to their defaults. Do not use them
unless debugging stuff.
Then the program will resample the map so that the player can play
on it at a reasonnable speed.
If map is too big, and it's often the case, then it will downsize it until
there are sufficiently few fighters so that the CPU can handle the job.
This, of course, is not rocket science. The bench calculation is a
somewhat brute-force approach of doing things. Formally, we would have
to run the map for good to figure out what is the right speed. Still,
this bench gives good approximations.
Previous versions of the game relied heavily on 'fighter-scale' to resample maps, but this is not the case anymore. The 'fighter-scale' is now a minor parameter which is used to upsize maps if they are too small. In 99.9% of the cases, the map is first upsized by 'fighter-scale' for this parameter is by default set low (1.0) then downsized by 'bench-value' for real-life personnal computers can't handle 1600x1200 maps in real-time. Not yet.
There are a bazillion options to control map size, including 'min-map-surface'. They are here because it's important that, ultimately, people can do whatever they want with the game. But for map design, this is another story. Don't use them. Rely on 'bench-value' and just care about game speed. This is achieved by changing the “speed” parameter.
It is possible to store your own custom music file within the map directory.
You can call it whatever you want (you can keep its original name, which is
something music authors usually appreciate, even if there's no strong
“attribution” clause on the license, it can be considered fair use not
to fiddle to much with the name) you just have to place it in the same
directory than the other files like map.png
or texture.jpeg
.
The following formats are known to work with the default
SDL_mixer based mod_ogg
backend:
ogg
(Ogg Vorbis files)
wav
midi
(extensions .mid
and .midi
should both work)
mod
, s3m
and xm
files, AKA “modules”.
To be more precise, here's how things work:
music-file
(parameter taken
from style.xml
or defined/overriden by player) in the current map
directory;
step 2: if not found, it will try every path in music-path
to find
this file. This includes the “system” music directory with musics that
ship with the game, but also the ./music
subfolder in the user
directory;
step 3: if still not found, it will try to play a random file, relying
on music-filter
to ignore some files.