http://www.quakelive.com/

Quake 3 in a browser...

So they want me to play Far Cry 2 on a browser ? Ha ! I may have an 8MB pipe which I quite appreciate, but I don't think any 3D game worthy of the name is going to be played in a browser window any time soon. Even if the technology is there, the available bandwidth is not. And that doesn't even take into account the customers of ISPs who throttle everything down as soon as you have used your full bandwidth for more than a minute.

I mean VRML anyone? Sure, it wasnt actually widely adopted, but it was meant to be 3D web. The problem is - who cares? 3D doesnt add enough to text or video to make it anything other than something that will make more sites gimmicky and harder to use. And we already have Flash (and to a MUCH lesser extent) and Silverlight to do that for us.......

The reason for doing this and not a plugin is that plugins are usually platform and/or browser specific.

A 3d markup language would be platform agnostic

...although it is nice to hear that the leading industry consortium is on board.

This one requires a plug-in but is fully functional for games developed on the platform:

http://unity3d.com/gallery/live-demos/tropical-paradise

It's been done.

http://www.instantaction.com

But, it's a good idea none-the-less