very interesing article! I am also looking for a uinity3d-viewer working with opensim. Is it possible to download the viewer somewhere?
Thanks in advance!

An Unity project can be integrated in a web browser but also it can be build in a stand-alone viewer (an exe file) like SL, Hyppo or Naali. And it can even be deployed on an iPhone.

Ogre and Irrlicht are 3D engines. Unity is a game engine; it mean that it also includes Physics, Network, AI, Animation, GUI, Terrans/Levels Editor, Audio, etc …

This is a great summary of the things you found with Unity3D. It’s interesting that WebClient doesn’t work and i wonder if it might be possible to circumwent that sandbox by changing the way the Unity webapp is registered to the browser (it is possible to indicate a secure context for ActiveX – although it will still refuse to elevate from Low privileges, so you need to be careful about File I/O – but I’m not really sure about other technologies). Also, I would miss the ability to use native libraries (if I understand correctly, P/Invoke is not possible?). For Jpeg2000, CSJ2K might be a good solution on the client side if you can’t use native code with wrappers.

Neil:
Unity3D has a powerful graphics engine and great demo contents. Rei has a similarly powerful graphics engine, and the main issue lies in the contents. I can point to amazing games running on Irrlicht (or Ogre), but as long as OpenSim doesn’t support/have the sort of content (high quality meshes with custom shaders, environment-maps, lighting, etc), that is really irrelevant. Of course with Rei, you can always write custom SceneNodes or shaders, even custom logic with Plugins and there is already a similar experience to unity’s API with Javascript integration. And if you are still unsatisfied, you can always pick the engine apart – although having done that a couple of times, I’m not sure I’d recommend it I guess what Rei really lacks right now is some kicking demo contents – but that will change soon.

Well, I guess – as Rob said – in the end what it comes down to is weighing the pros and cons between super-easy and super-flexible.

Personally I haven’t dug around in the 3Di Rei code yet but it looks promising from what i have read/seen on blogs etc. The benefits of the 3Di viewer are that everything in it is open and of course free this leaves more flexibility for changes down at the graphics engine level.

With Unity3d you have to rely on the provided APIs which are vast and flexible though at some point may prevent you from doing something. However with Unity you’ll be piggy backing on the extensive testing done by the Unity3d guys on hundreds of graphic cards which is bound to reap rewards in terms of stability of the client. From my experience it is a lot quicker to write games/clients with Unity3ds c# and javascript API support than it is doing pretty low level c/c++ development with the ogre3d or irrlicht engines. You can still do pretty low level stuff with Unity (creating shaders or doing direct GL commands)

There are pros and cons to all of these virtual world client solutions, writing a client is never going to be an easy business and i guess that’s why i favour unity as its APIs and editor environment make some of the heavy lifting a lot easier.