Package Structure

A holoocean package is a .zip file containing a build of holoocean-engine that contains worlds and Scenarios for those worlds.

A package file is platform specific, since it contains a compiled binary of HoloOcean.

Package Contents

The .zip file must contain the following elements

A build of holoocean-engine
A config.json file that defines the worlds present in the package
Scenario configs for those worlds

Package Structure

The package.zip contains a config.json file at the root of the archive, as well as all of the scenarios for every world included in the package. The scenario files must follow the format {WorldName}-{ScenarioName}.json.

+package.zip
+-- config.json
+-- materials.csv
+-- WorldName-ScenarioName.json
+-- LinuxNoEditor
    + UE4 build output

config.json

This configuration file contains the package-level configuration. Below is the format the config file is expected to follow:

config.json:

{
   "name": "{package_name}",
   "platform": "{Linux | Windows}",
   "version": "{package_version}",
   "path" : "{path to binary within the archive}",
   "worlds": [
      {
         "name": "{world_name}",
         "pre_start_steps": 2,
         "env_min": [-10, -10, -10],
         "env_max": [10, 10, 10]
      }
   ]
}

The "pre_start_steps" attribute for a world defines how many ticks should occur before starting the simulation, to work around world idiosyncrasies.

The env_min/env_max attributes are used to set the upper/lower bounds of the environment, used when an octree is made for a sonar sensor.

materials.csv

This file contains acoustic properties of the materials found in the environments, used for computation of the sonar images. Below is the format the config file is expected to follow:

Material, Density kg/m^3, Speed of Sound m/s
M_Landscape, 3200, 4500
M_URockA, 3000, 5000

At the start of each simulation, this file is read so that it can be edited without needing to recompile the entire unreal binary. The first line is ignored, and is just used for reference when editing the file. The first column is the name of the material in UE4, the second is the material density in kg/m^3, and the third is the speed of sound in m/s. These are used to compute the acoustic intensity of the various materials found in the environment.

Note if a material is found in the environment that isn’t found in the .csv file, it will be appended to the csv file with a default density and speed of sound of 10,000 (which results in full acoustic reflection).