I often ponder what life might be like among Uploads: human minds which have been scanned into machines, leaving the flesh behind and spending most of their time in simulated worlds. (See, for example, Greg Egan‘s novels Permutation City and Diaspora.)
It could be that each household has a seamless private universe, into which others teleport when invited. This does not appeal to me, because it makes chance encounters impossible, and because I suspect we need some psychological distance from our neighbors.
So instead I assume that each private domain includes a door to a shared space (or several); and think about how such spaces might be designed and what their conventions might be.
A simulated space can of course be modelled on any of a thousand fantasy settings; each presents its own set of design problems.
But I reckon the most popular form is a city, with streets, fountains, parks, churches and so on, surrounded by scenery. When you cross a ‘county line’ you’re in another world, continuous with the previous but simulated separately, in a different style (realistic, painterly, cartoon) with different laws of ‘nature’.
(What happens if levitation is legal in some counties and not others? A flying carpet may abruptly become a plummeting carpet, but it still has horizontal momentum. A new sport suggests itself: finding the appropriate altitude and speed at which to cross the border so as to hit a landmark.)
I feel that the map (which in this case is the territory) ought to change over time: mountains migrate like sea-waves; islands swim around each other like Boids; buildings jostle (and negotiate) for position. The counties themselves might flow about like tiny tectonic plates.
So much for the environment, though the subject is by no means exhausted; now for the occupants.
Bodiless people in fantasy worlds can obviously manifest themselves any way they like. It will be interesting to see how many wear a grossly fanciful form – troll, centaur, cartoon wabbit – longer than novelty can explain. (And what does it feel like to shake hands with a cartoon?)
Within cities, people walk; the point of a city (in this context) is to encourage unplanned encounters, and a vehicle detracts from that. Fantasy bodies never tire, nor get flat feet. Of course horses – animated by Uploaded minds of real horses? – are used for sport and ceremony.
Size restriction seems likely in public places. In Neal Stephenson’s Metaverse (Snow Crash) your avatar can be no taller than your real body, which seems unnecessarily cruel to midgets. I propose a rule and a custom: maximum size is the same for everyone (say six feet), and it’s customary to stay somewhat smaller than that (say five feet) except when seeking attention.
Later: I have almost never been able to get anyone else to join me in such speculations; this thread in rec.arts.sf.science is the exception.