[Fwd: 3D UI issues from Mark Mine] > 2) send me a list of what you think are the most important fundamental
> issues related to 3D/immersive manipulation that need to be discussed
> and written about

1) Extensibility
2) Extensibility
3) Extensibility
4) Integration of extensible interaction paradigms

Basically, there are a lot of cool interaction ideas that work well in
limited domains, but no one has managed to pull together these techniques
into a decent working system yet.  How can we do real-world work in a
virtual world?  How can we work for extended periods of time?

Other questions: 

1) The classic HMD vs. CAVEs question. I have to admit that I am leaning
towards the CAVE side right now (or projection/large screen interaction at
least).

2) How much of the "Magic" of VR depends upon 
   -  immersion
   -  head tracking
   -  stereo
   -  real-time 3D graphics