creating mirror image of islands

It's easy to get confused about terms like mirror, copy, and replicate. Going
forward, I'll be using these definitions:

  replica - another instance of the semantically SAME object that someone else
might have. Replicas share identity. Croquet works by replicating objects
(memory and messages) among the various participants of a simulation.

  copy - a semantically DIFFERENT object, within the same or a different
simulation. Replicas have different identity, but otherwise have the same data
at the time they are copied. Thereafter they may diverge.  (Unless someone says
otherwise, a Croquet copy is typically understood as a roughly "deep" copy. The
parent and class are typically identical in the two copies, while everything
else (including scripts and materials) is typically a copy.)

You replicate an island simply by joining an existing simulation. There are
various techniques for making it easy for people to join, including:

* The SimpleDemo's serialized postcard example (Tools->What's My Location /
Tools->Connect to Another Word).

* The KAT demo's ability to copy a portal and carry or paste it to another
island that you have access to.

The KAT code let's you copy any object in the space, but not currently the space
itself. You can paste objects into the same or different worlds, and onto each
other to form assemblies that can then be copied as a unit. You can also grab
any number of objects simultaneously (including, for example, a previously made
copy of each interesting object in a space), and then drive or teleport to
another world. When you arrive in the other world, you will still be carrying
(copies) of the the objects you had been carrying, in the same geometric
arrangement as when you picked them up.  See the context menu on objects in the
KAT demo. (cmd/alt-click on the object.)

You cannot currently drag an object into another world (e.g., standing in one
world and dragging an object through a portal to another before releasing).

At one time, the Wisconsin team experimented (WiscWorlds) with an automatic
interface for duplicating (copying) whole worlds. You could cache a snapshot in
time of the current world (as you still can in the KAT demo). In another session
later on, if you opened a portal to join a world, it would check for both an
online current version AND a previously cached snapshot. If there were both, it
would ask if you also wanted a second portal created for you that pointed to a
(now renamed) copy of the previously cached snapshot. We felt this was far too
confusing to be useful, and decided that it was much better to work on making
the online worlds reliably available.

Kiran wrote:
> Hi,
> Is it possible to replicate among the islands kind of drag and drop
> facility to make a replica of an existing island in Croquet space?
>
> Thanks
> Kiran

--
Howard Stearns
University of Wisconsin - Madison
Division of Information Technology
mailto:[hidden email]
[hidden email]
voice:+1-608-262-3724

On Feb 20, 2007, at 6:20 AM, Kiran wrote:

> Thanks for the inputs Howard.
> I did try out KAT demo and found the copy and paste functionalities.
> But, Is it possible to copy the contents ( say type Cube in Text
> application) and then paste it (letters) on to say Cube as a title
> on its surface?

Not yet.

>
> This could be extended to grabbing textures and pasting it onto
> cube/spheres in the space, if the above is possible..
>

That is the way it works.

You can Copy Material from objects (including window panels), and
paste them onto other objects.

A window panel is a rather odd thing. It has a front cover (a 2D
rectangle) a back cover (another 2D rectangle) and contents. When you
open/close the window, it swaps the front cover and contents.  So
Copy Material grabs the front cover material if the window panel is
closed (covered), and the back cover if the window panel is open
(such that the front panel isn't visible).   Confusing, no?

This is how we interactively construct the covers on the various
portals and movie players. We drag in pictures (which are actually
implemented as "empty" window panels with no "contents") and then
Copy Material (to get the texture from the front cover) and then
Paste onto a closed portal window or video player window.

Some kinds of window panel content are not currently copyable,
including text, VNC, and portals.  However, MPEG movies and live
streaming Web-cam video appear as the content of window panels and
can be grabbed as Copy Contents (whether the window is open or
closed).  The resulting material can be pasted onto other objects and
controlled (to play or not) via the original window panel.

There have been a couple of bugs reported lately in the KAT,
including two involving the previous paragraph.  Users should update
their Wisconsin package using Monticello.