Re: [ogpx] URI schema for virtual world locations?

[Carlo Wood <[e-mail]>]

On Fri, Jan 22, 2010 at 11:13:46AM -0800, Meadhbh Hamrick wrote:
> 1.3. there may be two forms of location representation: absolute
> position within the virtual world (as denoted by a single point in
> space) or relative to the origin of a region.
> 
> 1.4. the statement above (1.3) implies there is a public service
> available to map between points in the absolute space of the virtual
> world and points relative to a region.

It is not true that the relative position of any two arbitrary
regions is known. For example, some world could consist of
of planets in solar systems and some would simply be too far
apart to use coordinates in meters. Another example are
the islands of private sims in SL.

Hence, it makes more sense to limit coordinates to a Cartesian
coordinate system relative to a given region, and be have
a public service that maps region name pairs to a relative
position vector v(name1,name2), or returning nil if they are
not in the same space.

The distance between {name1, v1}, where v1 = {x1,y1,z1},
and {name2, v2} is then v(name1, name2) + v2 - v1.

That way a world is not obliged to have one single space
where in every region must have a place.

Also, putting every region in one region will likely
lead to this 2D plane with regions and a z-coordinate
with a range equal to that of each region: a flat world
(like SL). I hope everyone knows that ANY example that
breaks a protocol is prove that the protocol is wrong ;),
so here it goes: someone might want to create "ring world"
(http://en.wikipedia.org/wiki/Ringworld), where the
rings exists of square regions, and the diameter of the
ring is too large to really want to use it. Such a world
could not very easily map it's world positions to a
flat one (or even x/y/z, without getting really large
and seemingly random numbers).

A better approach therefore seems to be:

A Cartesian coordinate system for one region at a time.
A map from region names to a 2-dimensional *map* coordinates,
where the map coordinates might have any arbitrary relationship
to world coordinates (being irrelevant), including the
notion that two regions might not be in the same space.

This would allow painting a map on a 2D surface (which can
be used to explore and retrieve LM's from), but it would
NOT allow to calculate the (real 3-D space) distance between
points.

1.3. there may be two forms of location representation:
map position (longitude/latitude) that give regions in a
given space, a place on a map, and cartesian coordinates
relative to the origin of a region (x,y,z).


1.4. the statement above (1.3) implies there is a public service
available to map between the {space, longitude, latitude}
"map coordinates" and points relative to a given region:

{space, longitude, latitude} <---> {region name, x, y}

-- 
Carlo Wood <[e-mail]>