realXtend speeds up the development of the global standardized 3D internet of virtual worlds by making the best technology available to everyone, and entirely free of charge. The true value of the interconnected 3D worlds is in the applications, not the platform.

You can create own networked multiuser 3d applications using realXtend as a base. Royalty-free, no strings attached, suitable for business. Pre-existing open source components and Internet standards are used when suitable, and new are created as needed.

realXtend is an organization that helps companies and people to collaborate on open source development and standardization. It is formed as two legal entities:

  1. the realXtend association, where the actual work is coordinated (largely on-line) and in which anyone is free to join as a member
  2. the realXtend foundation, which ensures the existence (owns and protects the name) and can be used for funding (the foundation can receive donations, and allocate them to realXtend development based on association’s recommendations).

The actual development work is mostly done in projects in the different companies and other organizations. realXtend is the collaboration to continuously develop the common platform on which applications are built.

realXtend technologies are now available also as part of the EU FIWARE Open Source offering in the WebUI chapter.


An introduction to the general architecture is presented in an article, An Entity-Component Model for Extensible Virtual Worlds (2011) (Alatalo, T. IEEE Internet Computing, 2011:30-37.)

Currently realXtend provides the following technologies:

The Original Tundra SDK (using Qt & Ogre3D)

The realXtend Tundra SDK is a complete 3d multiuser application development kit. It is a modular application that can be used both to run standalone applications (for example a single player game or a CAVE installation) and networked worlds. The same codebase is used both for server and client which are just different configurations. Tundra is the new name for Naali, which first started as a from the scratch client for the Opensimulator+ModRex server suite (aka. Taiga). With the addition of standalone functionality and a server module it was renamed to Tundra. Tundra uses Ogre3d for rendering and Qt for UI, Javascript support using QtScript and several other things. Bullet is used for physics.

Tundra is divided into the Tundra core and additional plugins and application level features. This division is illustrated in https://github.com/realXtend/doc/raw/master/tundra.png and the parts are documented in http://www.realxtend.org/doxygen/

For multi-user applications Tundra is used as the server also for the WebTundra client.

WebTundra – the browser based realXtend client

With the advent of 3D & realtime communication technologies in Web browsers we have implemented a HTML5 based Tundra client: WebTundra. It lives on GitHub: https://github.com/realXtend/WebTundra

WebTundra uses the popular three.js library for graphics with WebGL and includes an implementation of the Tundra protocol in Javascript over WebSockets.

It is mature and in commercial use as the base for the MAPGETS service and in the Finpeda Virtual Space product.


Tundra-Urho3D is a new native (C++) implementation using the open source Urho3D engine. This Urho3D based Tundra does not use Qt for the UI but is smaller and lighter. Urho is also suitable for iOS and Android mobile clients / applications.

In early 2016 we have also added server capabilities and Javascript support to Tundra-Urho3D. This is to have a smaller and lighter Tundra server implementation.

Tundra-Urho3D is available on GitHub: https://github.com/realXtend/tundra-urho3d

realXtend and Virtual Worlds

realXtend technologies are not limited to virtual worlds but can be used for many kinds of applications. Here the term ‘virtual world’ refers to the bag of functionality that people expect from a complete virtual world system such as Second Life ™.

realXtend does not currently provide a complete virtual world solution (a Second Life clone), with authentication, avatar editing, simple world creating tools, inventories, virtual currency, social groups etc.

We emphasize ease of integration to existing systems: both to Internet services and internal e.g. corporate backends. Instead of coming up with realXtend-specific authentication, typically it is better to use e.g. OpenID (Google, Facebook etc. accounts) or whatever your organization is already using (e.g. LDAP). Or just provide anonymous service which is typical for websites.

Assets (i.e. data files such as meshes and textures) can be put to normal web servers, special Second Life style inventory systems are often not needed.

However, the original inspiration for the initiative is from Second Life (http://www.ugotrade.com/2008/04/03/realxtends-vision-for-open-virtual-worlds-interview-with-juha-hulkko/). Several realXtend applications and business ideas share a lot with virtual worlds and some realXtend people advocate the so-called 3D Internet etc.

It is possible that a distributed Internet wide new open source & standard Second Life like thing emerges from these efforts. The Hypergrid system with Opensimulator is approaching it from a different angle. We discuss constantly with Opensimulator people about possible cross-compatibility and interoperability.

Currently the Tundra repository hosts simple example / reference Avatar, Chat and Voice applications (written in Javascript on top of the base C++ level functionality). The scope of virtual world functionality efforts under the realXtend umbrella is open for discussion.

Welcome to the realXtend community!

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