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From: skinner@saber.UUCP (Robert Skinner)
Newsgroups: net.graphics
Subject: XOR cursors
Message-ID: <1858@saber.UUCP>
Date: Fri, 8-Nov-85 14:37:57 EST
Article-I.D.: saber.1858
Posted: Fri Nov  8 14:37:57 1985
Date-Received: Sun, 10-Nov-85 08:34:31 EST
Distribution: net
Organization: Saber Technology, San Jose, CA
Lines: 56

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A while back a discussion was started about someone who owned the
patent to doing non-destructive cursors by XOR'ing.  A friend of mine
discussed this not long ago with the owner of the patent, because my
friend was infringing on parts of the patent.  By the way, this
company is not asking just $100, but $10K-25K, depending on the extent
of the infringement.  

The company is CADTRAK of Sunnyvale, CA.  They made a workstation
aimed at chemical plant design, but have since scrapped that, in favor
of porting the software to PCs using TECMAR graphic boards (which
probably infringe on the same patent).  Supposedly the president was
seen at Siggraph, talking to various vendors.  Asking how their hardware
did this or that.  Depending on the answer, he would give them the
info on this patent, and hit them up later for money.

Here is a brief list of the items covered under patent #4197590, granted
in 1980, and an addendum #31200, granted in 1983.  The descriptions
given to me was terse, I'll expand a little on some that may not be
obvious.  

*  Use of hardware to XOR cursors non-destructively
*  Hardware for generation of the shape and location of a cursor.
*  Hardware image zoom by pixel replication 
*  Pixel replication zoom by a scale factor
*  Hardware for smooth panning (for apparent animation)
*  Hardware grid patterns mixed with the video
*  A method of modulating the video (after color table lookup) for
   generation of matte backgrounds (this I didn't fully understand)
*  Double Buffering image memory
*  The simultaneous display of two separate image buffers on one video
   display.
*  Read skip control: selectively skipping the readout of portions of
   image memory.


From what I think I know about the CADTRAK workstation, my personal
opinion is that it did a lot of unique and innovative things, e.g.
simultaneously displaying two parts of the image buffer and panning
each independently.  It seems as though while they were patenting the
innovative features, they went for the works.  I'm almost more disappointed
in the patent office for granting this (in 1980 even!) than with
CADTRAC for taking advantage of it.  Any other comments I'll reserve
for those on the net.

------------------------------------------------------------------------------
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Name:	Robert Skinner
Snail:	Saber Technology, 2381 Bering Drive, San Jose, California 95131
AT&T:	(408) 945-0518, or 945-9600 (mesg. only)
UUCP:	...ihnp4!saber!skinner