OpenSimulator is a free open source server of 3-D environments. It is multi-platform, and the environments it serves can be accessed by various clients using various protocols. The official homepage of the project is

It is written in C#, which can be run using Microsoft's .NET framework or the free open source Mono framework.

It has typically been sufficiently compatible with Second Life that people could use Second Life clients to access environments served by OpenSimulator, however it is not intended as “a Second Life clone”. It in fact supports things that Second Life does not, such as the Hypergrid.

According to its website, it is even less aimed at gaming than is Second Life; however what specific features Second Life provides that specifically support gaming is not elaborated; at least one relatively popular gaming system used in Second Life is also used on at least one commercially-oriented OpenSimulator grid.

Although its develpers still consider OpenSimulator to be alpha software, it is relatively mature technology, and has reached a point where almost anyone can use it to serve a virtual 3-D environment from their own home. There is even a server on a USB stick offering specifically for this purpose.

Because various people have from time to time suggested that in this day and age no-one wants to play games that do not provide a 3-D immersive environment, the Galactic Milieu project has been following various projects that aim to provide such environments, including OpenSimulator and Worldforge. While Worldforge seems to have largely stagnated for the last decade or so, OpenSimulator has made great progress, making it now proably the top contender for 3-D presentation medium of choice for the Galactic Milieu.

The term presentation medium carries the implication that while OpenSimulator might not yet be useable as a means of actually playing various aspects of the Galactic Milieu it might nonetheless have reached a point where it could be used to render various views of various aspects of the Galactic Milieu. For example players who wish to have a 3-D representation of their dwelling, or of some village, town or city they have built, or even just of some character in the game, might well be able to use OpenSimulator to achieve such a goal.

OpenSimulator uses “grids” of “regions”, treating height somewhat differently from the two dimensional grid of regions. Looked at as a possible media for rendering the surface of a planet it thus comes across as basically two-dimensional, in that the basic grid is two dimensional rather than three dimensional. Regions are taken to be 256 metres by 256 metres, so to represent one square kilometre of terrain would take most of a four region by four region grid of regions. Considering that the map tiles used in Freeciv are probably about 100 kilometres to 100 miles or more across it is clear that representing an entire Freeciv world would require a large number of OpenSimulator “regions”. Thus however much players might like the idea of such complete representations of worlds it seems clear that to keep the cost per player down to some price players will actually find acceptable it will probably be necessary to fudge somehow, either by dynamically generating virtual regions to fill huge amounts of unused space between regions that actually have players present in them at any particular moment or by only bothering at all with OpenSimulator representations of limited areas that for some reason players find worth the cost of representing in such a medium.

OAR The OpenSimulator Archive (OAR) function has existed since OpenSimulator 0.5.9. The facility does a similar job to load-xml2/save-xml2 in that it saves prims so that they can be later reloaded. However, OpenSimulator archives (OAR) go a step further in that they can save all the necessary asset data so that you may fully restore the terrain, region parcel data, the textures of objects and their inventories when loaded onto a completely different system using a different asset database.

IAR OpenSimulator Inventory Archives (IARs) are a means by which inventory folders and items can be saved offline to a single file (an IAR). This file can then be loaded into a different OpenSimulator installation.

Like OpenSim Archives, IARs save all the necessary asset data required to fully restore the items including textures, sounds, scripts and objects contained in the inventory of other objects.

IARs have been enabled in OpenSimulator since Git revision 5a64ca (OpenSimulator 0.6.7 and later).

MESH OpenSimulator supports the use of collada meshes. It must be noted that at the time of this writing, mesh support is still under development at Linden Labs, and they make changes to that all the time. Therefore, they can not guarantee that the current implementation of mesh support in OpenSimulator will be 100% compatible to the final version on SecondLife, once that gets rolled out. If you plan on using OpenSimulator to develop meshes for SecondLife, make sure you update Opensim frequently.

Freeswitch The FreeSWITCH module enables voice in OpenSimulator with no changes required to the Linden Labs Second Life viewer. For OpenSimulator and earlier, the viewer must be between versions 1.22 and 1.23.5. For OpenSimulator 0.7.1 and later 2.x viewers will also work.

D4OS These Drupal modules can use the database directly (the bases can be on the same server as drupal7 or be separated) or they can control services like Radmin or OsServices or control another drupal website that can access the base directly using webservices.

Open Source

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