Command line application for converting OpenSimulator OAR files into various other formats
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Command line application for converting OpenSimulator OAR files into GLTF scene file.

An OpenSimulator OAR file saves a region's contents. All the information about the region (parcels, terrain, etc.) is saved in an OAR file along with all the objects and their locations (prims, meshes, scripts, textures, etc.). Thus, an OAR file of a region is convertable into any other scene representation format.

Convoar reads an OAR file and outputs a GLTF scene and image files which is most of the region information. Most specifically, it outputs the textured mesh representation of all the objects in the region.

Convoar is evolving. See the "Releases and Roadmap" section below. The current version reads an OAR file and outputs either an unoptimized GLTF scene file or a "material reorganized" GLTF scene (see below). The output GLTF is not packed or binary so the output files are a JSON .gltf file, one or more .buf files (containing the vertex information), and an images directory with the texture files for the mesh materials. By default, the output textures are either JPG or PNG format depending if there is any transparency in the texture.

The unoptimized GLTF conversion is a simple conversion of the OAR primitives which creates many, many meshes and is very inefficient for rendering but is good for editing (importing into Blender, for instance).

The "material reorganized" scene has objects corresponding to each unique material (texture/color/features) and the meshes have been assigned to each of these material objects. This renders the scene uneditable but this should greatly reduce the number of draw calls needed to render the scene in OpenGL/WebGL.

Future versions of convoar with either contain or have tools to perform other optimizations to the scene and the object therein.

The name "convoar" is from "convert oar" and is pronounced like "condor". There is a logo idea in there somewhere.


Checkout the convoar sources and run the prebuilt binary in the dist directory. The binaries are compiled for .NET Framework 4.6 so you must install that library version better on Windows10 or, if running on Linux, Mono v4.2.1 or better.

git clone
if Windows:
convoar/dist/convoar.exe region.oar
if Linux:
mono convoar/dist/convoar.exe region.oar

The full invocation form is:

convoar <parameters> inputOARfile

A short list of the available parameters (a boolean parameter can be followed with a true or false):

Parameter Meaning
--mergeSharedMaterialMeshes or -m reorganize all meshes in the scene into groups using the same materials. This makes the scene uneditable but will make for way fewer draw calls when displayed.
--outputdir or -d directory for generated GLTF and image files. Default is `./convoar'.
--regionName Name to use for generated scene. Default is name of input OAR file.
--textureMaxSize Maximum size for textures. All images are resized to less than this dimension. Default is 256.
--halfRezTerrain Whether to reduce terrain resolution by two. Default is true.
--createTerrainSplat whether to create a terrain texture based on height. Default is true.
--verbose or -v Output information on numbers of meshes, etc.
--help list all available parameters with descriptions and default values

An invocation of convoar ../REGION.oar will create, in the output directory, the files REGION.gltf, one or more REGION-bufferNNN.buf files, and an images directory containing .JPG and .PNG files. The GLTF file will reference the images directory and the .buffiles so the relative directory position of the.buf and images files is significant.

The output directory is changed with the --outputdir parameter.


Convoar uses OpenSimulator sources to do the reading and conversion of the OAR file. These source files are included in this repository. So there is a simple build where one just builds the sources checked out, and there is the updating build where one fetches new versions of the OpenSimulator sources.

Simple Build

Under windows 10, use Visual Studio 2017 or better. At the moment, convoar is built under Windows to create the dist directory. The prebuilt binaries will run on Windows10 and with Mono on Linux. There are no external dependencies -- everything is included in the Convoar GitHub repository.

If compiling on Linux, one needs Mono version 5 or better and one just uses msbuild.

Updating Build

To update the OpenSimulator sources, the script fetches the required DLLs from other repositories. The other repositories must be cloned into the same directory as the convoar repository so the steps could be:

git clone
git clone git://
(build OpenSimulator)
git clone
(build libOpenMetaverse)
git clone
(build C-Sharp-Promise)
cd convoar

Then convoar can be built using either Visual Studio or msbuild.

Docker Image

For those with Docker environments, there is a Docker image of convoar.

Assume the OAR to be converted is at /tmp/frog/REGION.oar. Then, to do the conversion:

docker pull herbal3d/convoar
docker run --rm --user $(id -u):$(id -g) -v /tmp/frog:/oar herbal3d/convoar REGION.oar

This maps the local /tmp/frog directory to the /oar directory in the Docker container, runs the container, and writes the output GLTF files into the /tmp/frog directory.

NOTE: the most common problem is permissions. The command above, sets the user and group IDs to that of the current user (the --user parameter) which is usually is the right thing for write permissions into the mapped directory.

Releases and Roadmap

  • Release 1.0
    • basic OAR to GLTF conversion
    • material-centric optimization
  • Release 1.1
    • cleaned up and debugged command line and Docker version
  • Release 1.2
    • option to include all prim information in extras (scripts, notes, etc.)
    • pipeline tools in Docker image for binary/DRACO packing of GLTF file
    • invocation options to select sub-regions of OAR region
  • Release 1.3
    • pipeline tools for scene optimizations (small mesh elimination, mesh decimation/simplification, etc.)