TECH Survey comments

John W. Barrus (
Sat, 30 Jul 94 23:49:53 EDT

Cached object support

Although at the beginning of the discussion, I thought this was a bad idea,
I have changed my mind. However, I still don't like the idea of having "my
refrigerator" replace "your refrigerator" when I move into your space using
vrml. However, if I have visited your space, I could have retrieved "your
refrigerator" once before and cached it. Then I could call up "your
refrigerator" from my local hard disk. In other words, my vote for Cached
object support is NEVER as described in the survey, but I do see a definite
need for some caching.

Another approach to caching would be to create long (32 or more bits) ID
numbers for each object (based on the creator of the object and the time of
creation). When we download objects, if we have cached the object with that
ID, we simply read in the object locally. When we clean out our local
cache, we might keep a database of ID's and where we have seen those objects
before, along with some indication of how good the connection was when we
downloaded that ID (bytes/sec download time). We could then choose to read
that object from the machine that has the best connection (and then update
the "quality of connection" data for that computer).

For instance, if I "borrow" (with permission, of course) a refrigerator
(ID number 2948375674837) from an international site with a slow connection
for a scene that I have built and someone visits my scene before visiting
the international site where the object originated, they can either re-use
the refrigerator they got from me, or download it from me again if their
connection to my machine is better than the connection to the international

- always getting the correct object (not just something similar to that
- good speed-up in communication without huge cache space requirements.
- could set up a cache on a local machine that contains the cache for all
of the machines at your location and you would never have to keep a cache
on the machine that you use (as long as you update the ID database on
all of the local machines correctly).
- You see what the designer of the scene wants you to see.
- no class definitions required.

John B.
John Barrus
Mitsubishi Electric Research Laboratories, Inc.
201 Broadway Phone (617) 621-7535
Cambridge, MA 02139 FAX (617) 621-7550