JPS images???

[P3D Larry Berlin <lberlin@xxxxxxxxx>]

>Date: Wed, 23 Apr 1997 
>From: P3D Andrew Woods asks:
>..........................
>p.s. what is JPS LCD format?  
>
>Does JPS refer to the JPEG compression format?  If so, be careful...
>JPEG is lossy compression and can therefore lead to crosstalk in 
>3D interlaced images.  GIF format would probably be better (unless a very
>low JPEG compression ratio is used).
>
>I guess the "LCD" refers to Liquid Crystal Shutter glasses.
>The group informally decided to use the abbreviation "LCS" some
>months back to avoid misuse of the term "LCD" (because there are
>no LC displays used) and to avoid confusion with HMDs (Head mounted
>Displays) which do use LCDs.
>
>Incidentally I tend to use the term "3D interlaced" to refer to 
>images which are interlaced for viewing with LCS glasses.

You correctly identified JPG out of JPS. JPS is a standardized format agreed
to by several manufacturers of LCS viewing systems. It is available for all
existing types of systems. I have the Total 3D system which uses a whole
complete image which is rapidly page-flipped for stereo. Interlaced 3D
images use only 50% of the original image by putting both images in the same
space, alternate lines.

There was a need to develop a standard for internet usage of 3D images.
Since that means largely a choice between JPG or GIF, the choice was pretty
obvious to go with JPG. Other formats will be adopted in a similar way in
future. I'm waiting for PNG, which offers many advantages especially a
no-loss compression for full color images. It sounds perfect for stereo
applications. PNG would be used in the same fashion, but hasn't been set up
for the viewers yet as they are waiting for the format to gain a greater
support in the industry overall.

Essentially the JPS format calls for a side by side stereo pair with the
right image first. The two halves must be of equal size, in pixels because
the various viewers assume this to be true and divide it down the middle for
display. After saving as JPG at your choice of compression, change the G to
an S and it's ready to load into whatever viewer you are using. It's very
convenient because it's standard and most graphic programs include JPG
capability. They are crossed, because the job of aligning, windowing, etc,
is greatly enhanced by the ability to actively view the pair as you make the
adjustments. If you can cross view, you will want to view as you work. If
you can only parallel view, the images at normal size are frequently to
large to fuse without something like the Freeviewer's Assistant. For those
who don't freeview, it doesn't matter.

One other detail of JPS format is that a number of special *descriptors*
have been developed for certain special circumstances. It requires a special
but free program to set these descriptors and make them part of the file.
They are not required, but handy for some of the systems out there. A file
opened and saved in ordinary graphics programs loses that descriptor.
Eventually there will be a plug-in for Netscape that allows JPS files to be
easily viewed in any method you prefer, including the ability to view that
same JPS file in Anaglyph as color or grayscale, crossed, parallel,
interlaced LCS, or page flipped LCS. More on this as it develops....

The primary purpose of a special file extension is so that browsers, and
viewers can be called upon when the file begins to download. The advantage
of using JPG as the basis makes it usable by everyone and not dependent on
any particular brand of equipment. If you wish to view JPS files there are
several sources on the internet. I have a few on my pages and a bunch
getting ready to post. Canopus (linked from my site) has a gallery of JPS
files, including a number of computer graphics I created for them to use.
Since they are essentially JPG images, you can enjoy them by simply saving
to disk and changing the extension. Generally these are intended for LCS
viewing and are of a large size to take advantage of the potential of full
screen display. For that reason, they will not be the typical small image
common to many stereo images on the internet. I put smaller images for
general viewing and provide a link to download the larger JPS files for more
optimum viewing.

I've changed all the anaglyphs I've collected from the Internet to JPS
grayscale pairs and enjoy them far more than viewing through red/blue
glasses. The large scale and better resolution make this method superior for
stereo images, at least on the internet.

If one is concerned with the loss of a  JPG file, one's own images can be
whatever no-loss format is desired. Then when saving as JPG, don't compress
the image.

I encourage all who have stereo websites to make use of this file
arrangement so that people with viewing systems can easily access your
images at their best. You will probably use your ordinary methods on the
pages themselves, but a simple link makes them available to the public. You
will have to arrange with your Internet Service Provider to use this file
type on your pages. It doesn't cost you anything and all you have to do is
ask that file type x-jps be added to their system. 

If you have a need for more specific information on this, please email
directly. 

Larry Berlin

Email: lberlin@xxxxxxxxx
http://www.sonic.net/~lberlin/
http://3dzine.simplenet.com/


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