Wiki » History » Revision 30

« Previous | Revision 30/83 (diff) | Next »
Josip Almasi, 10/15/2021 03:14 PM


External resources

Demo site:

Github project page: article (motivation):

VR Days video (features, technologies):

Youtube channel:

Facebook page:

Client API jsdoc:

Server javadoc:


Multi-user interaction, shared objects:
Multi-user world:
Avatar selection, portals:
VR Avatar template world:

Frequently Asked Questions

Is this open source, free to use and share?

Yes, it's all free and open. Server and client code is published under Apache 2 license, all 3D models published by their respective authors under Creative Commons Attribution license.

Is there any documentation?

This is good place to start, this page links to all available resources.

How many users can share a “world/space” simultaneously?

By default, number of users per space is not limited. There is a server parameter to limit that (org.vrspace.server.maxSessions) that can be specified either in config file or command line. Users that hit the limit remain in the queue for configurable timeout (org.vrspace.server.sessionStartTimeout, zero by default) until someone leaves. An error is raised on timeout.

Setting up development environment

Here's all you need to start development on Windows.
Linux distributions include all these tools as native packages, so no additional downloads should be required.

Basic setup

Git bash

IDEs can work with github directly, but whatever you ask, you'll get a command line answer.
Command line git is simply a must have. Bash also includes a lot of goodies like ssh.


Java 8 will work, java 11 recommended. JDK is required to build the server.
Get it either from Oracle or elsewhere, e.g. Zulu OpenJDK:


Node is used by IDE to evaluate javascript. You'll also may need it if you modify any of babylon.js source.
Mind that IDE will complain if you installed unsupported version of Node; should that happen, remove Node, and install latest one supported.

Get it from


Apache Maven is used to build the server from command prompt.

Get it from


Eclipse for Java developers (not enterprise), with Spring and Web plugins:

Download eclipse here:

And then go to Help -> Eclipse Marketplace
Search and install Spring Tools 4 and Wild Web Developer plugins.

You'll also need to download and install
Once done, restart the eclipse.

Import and start the project


In Eclipse, you can use either default or new workspace for the project.
Assuming you have cloned the project from the github,
Go to File -> Open Projects From the Filesystem
Then choose vrspace directory.

This will import vrspace folders and project subfolders, click Finish.

In vrspace project folder, in src/main/java, there's
Open it, then right click on the code.
From the menu, choose either Run as or Debug as -> Spring Boot App.

Open http://localhost:8080/babylon/connect.html with two browsers, and navigate around.

That's all, you're all set!

git bash

git clone
cd vrspace
mvn clean install
java -jar server/target/server-0.2.2.jar

Advanced setup


HTTPS is required for pretty much everything - WebXR, camera, mic access.
By default, the server runs on 8080 port with plain HTTP. To enable HTTPS, edit (found in src/main/resources), and change following properties:

# default port 8080


Apache reverse proxy setup, linux, windows, TBD

Docker and OpenVidu

OpenVidu voice/video chat server runs as docker image. This is only required for development of voice chat functions.

Local execution (development):
docker run -p 4443:4443 --rm -e OPENVIDU_SECRET=YOUR_SECRET -e DOMAIN_OR_PUBLIC_IP=YOUR_IP openvidu/openvidu-server-kms:2.17.0

Running on server:

Then either modify openvidu.publicurl and openvidu.secret in, or run server.jar with -Dopenvidu.publicurl=YOUR_URL and -Dopenvidu.secret=YOUR_SECRET

Software Architecture

Client-Server Communication

Clients communicate with server over WebSockets. Reference javascript implementation of client communication layer is in VRSpace.js.

General approach to communication is rather obscure Half-Object pattern: server-side and client-side object have same properties, but different implementations.
Whenever an object's property changes in (any) client's address space, it's transmitted to the server, that broadcasts it to all clients currently 'watching' the object.

Whenever a client wants to perform any change to any object in the space, it has to go through the VRSpace server.
Clients may or may not communicate directly, but this is out of the scope of VRSpace server.

Server Responsibilities

Sole responsibility of VRSpace server is management of 3D space: persisting space objects, tracking their properties, processing and distributing events from/to objects.
Whenever we talk about objects, that includes clients, i.e. users - a client is a special case of an object.
The server does not even handle the authentication - it is assumed to be responsibility of web app serving the space.
3D geometry is also not in server's scope, it's just another property of an object (mesh).

Server design

Key concepts here are Active Objects, Actor model, and Live distributed object.

VRObject is a basic shared object, with some basic properties like position and rotation, and of course, mesh. It essentially a Live distributed object.

Client extends VRObject, and adds capabilities to communicate over web sockets, and listen to changes to other objects. Typically, a client represents a remote user, but it can also represent a robot connected over a web socket, or be a base class for a server-side robot.
A Client can be thought of as Active Object or an Actor,

Server relies on Spring Boot and embedded Tomcat to handle all I/O and threads.


Each Client has it's own Scene that tracks all shared objects - including other clients - visible by the client. The scene is initially populated once the client logs in to the server, and starts the session. Scene is refreshed periodically, after a movement, or explicitly.

Scene maintains the event model, by adding the Client as listener to all other active objects (usually other users) in the scene.

Client simply notifies it's own listeners on any changes to any of it's own properties. As a listener, it propagates any observed change on any other object over the network, to the user.

Client has just a couple of persistent properties, like position, rotation and name. The name must be unique.
All other properties are transient.


Typically events exchanged are changes to properties of active objects, e.g. user moves around, changing own position and rotation. However, an object may emit any event, and the event gets propagated to all listeners.
This is to simplify client development: simply emit any custom event you want.

Updated by Josip Almasi over 2 years ago · 30 revisions