Signs and Markers

The Overviewer can display signs, markers, and other points of interest on your map. This works a little differently than it has in the past, so be sure to read these docs carefully.

In these docs, we use the term POI (or point of interest) to refer to entities and tileentities.

Configuration File

Filter Functions

A filter function is a python function that is used to figure out if a given POI should be part of a markerSet or not, and to control how it is displayed. The function should accept one argument (a dictionary, also know as an associative array), and return a string representing the text to be displayed. For example:

def signFilter(poi):
    if poi['id'] == 'Sign' or poi['id'] == 'minecraft:sign':
        return "\n".join([poi['Text1'], poi['Text2'], poi['Text3'], poi['Text4']])

Note

This example is intended as a teaching aid and does not escape HTML, so if you are concerned that your Minecraft players will put HTML/JS into their signs, see below for a version that does do escaping.

If a POI doesn’t match, the filter can return None (which is the default if a python functions runs off the end without an explicit ‘return’).

The single argument will either a TileEntity, or an Entity taken directly from the chunk file. It could also be a special entity representing a player’s location or a player’s spawn. See below for more details.

In this example, this function returns all 4 lines from the sign if the entity is a sign. For more information of TileEntities and Entities, see the Chunk Format page on the Minecraft Wiki.

A more complicated filter function can construct a more customized display text:

def chestFilter(poi):
    if poi['id'] == "Chest" or poi['id'] == 'minecraft:chest':
        return "Chest with %d items" % len(poi.get('Items', []))

It is also possible to return a tuple from the filter function to specify a hovertext different from the text displayed in the info window. The first entry of the tuple will be used as the hover text, the second will be used as the info window content:

def chestFilter(poi):
    if poi['id'] == "Chest" or poi['id'] == 'minecraft:chest':
        return ("Chest", "Chest with %d items" % len(poi.get('Items', [])))

Additionally, you can filter based on other Block Entity data by including references to other Minecraft Block Entity fields. For instance, you can filter out world-generated lootable chests that have not yet been opened by players by filtering out chests that still have loot tables:

def chestFilter(poi):
    if poi['id'] == "Chest" or poi['id'] == 'minecraft:chest':
        if "LootTable" in poi:
            return None
        else:
            return ("Chest", "Chest with %d items" % len(poi.get('Items', [])))

Because of the way the config file is loaded, if you need to import a function or module for use in your filter function, you need to explicitly load it into the global namespace:

global escape
from html import escape
def signFilter(poi):
    if poi['id'] == 'Sign' or poi['id'] == 'minecraft:sign':
        return escape("\n".join([poi['Text1'], poi['Text2'], poi['Text3'], poi['Text4']]))

Since writing these filters can be a little tedious, a set of predefined filters functions are provided. See the Predefined Filter Functions section for details.

Special POIs

There are currently two special types of POIs. They each have a special id:

PlayerSpawn
Used to indicate the spawn location of a player. The player’s name is set in the EntityId key, and the location is in the x,y,z keys.
Player
Used to indicate the last known location of a player. The player’s name is set in the EntityId key, and the location is in the x,y,z keys.

Note

The player location is taken from level.dat (in the case of a single-player world) or the player.dat files (in the case of a multi-player server). The locations are only written to these files when the world is saved, so this won’t give you real-time player location information.

Here’s an example that displays icons for each player:

def playerIcons(poi):
    if poi['id'] == 'Player':
        poi['icon'] = "https://overviewer.org/avatar/%s" % poi['EntityId']
        return "Last known location for %s" % poi['EntityId']

Note how each POI can get a different icon by setting poi['icon']. These icons must exist in either the output folder, or in your custom web assets folder. If the icon file does not exist in the correct location, your markers will be shown without an icon - making them invisible!

Manual POIs

It is also possible to manually define markers. Each render can have a render dictionary key called manualpois, which is a list of dicts. Each dict represents a marker, and is required to have at least the attributes x, y, z and id, with the coordinates being Minecraft world coordinates. (i.e. what you see in-game when you press F3)

An example which adds two POIs with the id “town”, and then uses a filter function to filter for them:

def townFilter(poi):
    if poi['id'] == 'Town':
        return poi['name']


renders['myrender'] = {
    'world':'myworld',
    'title':'Example',
    'manualpois':[
                   {'id':'Town',
                    'x':200,
                    'y':64,
                    'z':200,
                    'name':'Foo'},
                   {'id':'Town',
                    'x':-300,
                    'y':85,
                    'z':-234,
                    'name':'Bar'}],
    'markers': [dict(name="Towns", filterFunction=townFilter)],
}

Here is a more complex example where not every marker of a certain id has a certain key:

def townFilter(poi):
    if poi['id'] == 'Town':
        try:
            return (poi['name'], poi['description'])
        except KeyError:
            return poi['name'] + '\n'


renders['myrender'] = {
    'world':'myworld',
    'title':'Example',
    'manualpois':[
                   {'id':'Town',
                    'x':200,
                    'y':64,
                    'z':200,
                    'name':'Foo',
                    'description':'Best place to eat hamburgers'},
                   {'id':'Town',
                    'x':-300,
                    'y':85,
                    'z':-234,
                    'name':'Bar'}],
    'markers': [dict(name="Towns", filterFunction=townFilter, icon="markers/marker_town.png")],
    ### Note: The 'icon' parameter allows you to specify a custom icon, as per
    ###       standard markers. This icon must exist in the same folder as your
    ###       custom webassets or in the same folder as the generated index.html
    ###       in this case, we use the marker_town.png icon which comes with
    ###       the Overviewer by default, located in a subdirectory of web_assets.
}

Render Dictionary Key

Each render can specify a list of zero or more filter functions. Each of these filter functions become a selectable item in the ‘Signs’ drop-down menu in the rendered map. Previously, this used to be a list of functions. Now it is a list of dictionaries. For example:

renders['myrender'] = {
        'world': 'myworld',
        'title': "Example",
        'markers': [dict(name="All signs", filterFunction=signFilter),
                    dict(name="Chests", filterFunction=chestFilter, icon="chest.png", createInfoWindow=False)]
}

The following keys are accepted in the marker dictionary:

name
This is the text that is displayed in the ‘Signs’ dropdown.
filterFunction
This is the filter function. It must accept at least 1 argument (the POI to filter), and it must return either None or a string.
icon
Optional. Specifies the icon to use for POIs in this group. If omitted, it defaults to a signpost icon. Note that each POI can have different icon by setting the key ‘icon’ on the POI itself. (this can be done by modifying the POI in the filter function. See the example above)
createInfoWindow
Optional. Specifies whether or not the icon displays an info window on click. Defaults to True
showIconInLegend
Optional. Specifies whether or not the icon is displayed in the legend. Defaults to False
checked
Optional. Specifies whether or not this marker group will be checked(visible) by default when the map loads. Defaults to False

Generating the POI Markers

Note

Markers will not be updated or added during a regular overviewer.py map render! You must use one of the following options to generate your markers.

The –genpoi option

Running overviewer.py with the --genpoi option flag will generate your POI markers. For example:

/path/to/overviewer.py --config /path/to/your/config/file.conf --genpoi

Note

A –genpoi run will NOT generate a map render, it will only generate markers.

If all went well, you will see a “Markers” button in the upper-right corner of your map.

genPOI.py

The genPOI.py script is also provided, and can be used directly. For example:

/path/to/overviewer/genpoi.py --config=/path/to/your/config.file

This will generate the necessary JavaScript files needed in your config file’s outputdir.

Options

genPOI comes with a few options of its own.

-c <file>, --config=<file>

The config file to use for the genPOI operation. This must be the same config file that you use for your normal rendering runs.

-q, --quiet

Outputs less information onto the terminal while running.

--skip-scan

Skip scanning the world for entities and tile entities. Useful if you only want to generate markers for players or through manual POIs, as you can speed up the genPOI operation considerably.

--skip-players

Skip reading and retrieving player data during genPOI runs. This is useful if you don’t plan on generating markers for the player locations.

Predefined Filter Functions

TODO write some filter functions, then document them here

Marker Icons Overviewer ships by default

Overviewer comes with multiple small icons that you can use for your markers. You can find them in the overviewer_core/data/web_assets/markers directory.

If you want to make your own in the same style, you can use the provided marker_base_plain.svg and marker_base_plain_red.svg as template, with a vector editing software such as Inkscape.