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 of 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':
        return "\n".join([poi['Text1'], poi['Text2'], poi['Text3'], poi['Text4']])

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":
        return "Chest with %d items" % len(poi['Items'])

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:

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
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.


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'] = "" % poi['EntityId']
        return "Last known location for %s" % poi['EntityId']

Note how each POI can get a different icon by setting poi['icon']

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:

This is the text that is displayed in the ‘Signs’ dropdown.
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.
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)
Optional. Specifies whether or not the icon displays an info window on click. Defaults to True
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


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

The –genpoi option

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

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


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

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

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

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

Options has a single option --config. You should use the same configfile as used for your normal renders.

Predefined Filter Functions

TODO write some filter functions, then document them here