PLEASE COMPRESS! (was Re: Height maps, etc.)

Brian Behlendorf ([email protected])
Tue, 9 May 1995 23:27:44 -0700 (PDT)


On Tue, 9 May 1995, Chris Marrin wrote:
> > > Of course, waiting for 40k heights over a 14.4 modem might try the
> > > patience of those PC gamers.
> > >
> >
> > Right, at least 4 minutes to load the scene...
>
> Why 4 minutes? Today's 14.4 modems typically get close to 2000 bytes/sec.
> with compression. The 40K grid would probably consume somewhere around
> 200Kb (avg. 5 bytes per value). Compressed at 8:1 25Kb, which would take
> 12.5 sec. I'm not sure how the 2 compression schemes would beat against
> each other but even at twice that much time, that's 25s.

To throw some numbers in here:

Lightscape's Operating room model:
<URL:http://www.lightscape.com/models/or.html>
Downloaded size: 9307619 bytes
gzip'd size: 828192

UCLA Department of Architecture model of the African American Unity Center
<URL:http://www.gsaup.ucla.edu/vrml/models/lightscape/exterior.wrl>
Downloaded size: 3686400
gzip'd size: 243355

Imperial College, UK, 3CRO protein
<URL:http://www.ch.ic.ac.uk/VRML/3cro.wrl>
Downloaded size: 252847
gzip'd size: 67311

The CAVE: The Cathedral
<URL:http://jaka.eecs.uic.edu/dave/vrml/CAVE/cathedral.wrl>
Downloaded size: 400745
gzip'd size: 15984 (THIS IS NOT A TYPO)

If you are putting up VRML files on your web site, please please PLEASE
gzip them. Every web server I've ever used knows to add a
Content-Encoding line* which tells the browser to gunzip it. Come to
think of it, I'm not sure if Netscape for windows and mac have gunzip
routines built in, so you might still want to offer links to both the
compressed and flat versions... but to not offer compressed versions is
doing your visitors a real disservice.

* - for Apache and NCSA's httpd, add a line "AddEncoding x-gzip gz" to
srm.conf, and any file like foo.wrl.gz will be properly labeled with

Content-type: x-world/x-vrml
Content-encoding: x-gzip

> 28.8 modems are
> fairly inexpensive and getting cheaper every day. They have even better
> compression. I'll bet the above scene would get down to under 10 sec.
> ISDN should be cheap enough for home installation within a couple of
> years. That will double or quadruple the speed again.

Years? 6 months. The bottleneck right now is actually cost of NTI's and
CSU/DSUs which should be under $300 by August. But by no means does this
mitigate the problem. :)

Brian

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