terry@uts.amdahl.com (Lewis T. Flynn) (06/27/90)
In article <563@dg.dg.com> mpogue@dg.dg.com writes: > > By the way, they also claim to have invented "split screen", too. It >attempts to cover horizontal, vertical split screen, and maybe hardware >windowing as well. Hardware pan and zoom is claimed, too. I thought Doug Englebart demonstrated text windows (a form of split screen) in his famous NLS demo at the '68 FJCC (along with the mouse and other neat stuff). If so, then any split screen patent should be invalid as a whole lot of people saw the concept. Terry
prl@ethz.UUCP (Peter Lamb) (06/27/90)
In article <1990Jun26.182359.2989@utzoo.uucp>, henry@utzoo.uucp (Henry Spencer) writes: > In article <555@dg.dg.com> mpogue@dg.dg.com writes: > > I think all it takes is an example of a commercially shipped system, > >that can be shown to have used the XOR technique, before the claimed date > >of Cadtrak's invention. > > Independent invention, even prior independent invention, does not necessarily > invalidate a patent. Prior *publication* generally does, as it is presumed > to make the idea well-known, but a handful of highly-proprietary systems > shipped earlier might not qualify. Newmann and Sproull talk about the use of reversible raster operations for cursors in `Introduction to Computer Graphics'. The earliest copy I have is 1979 (2nd edition), but there's a 1973 copyright (to McGraw-Hill) in the cover sheets. This is presumabably the first edition. The use of arithmetic modulo 2^n (ie XOR for one bitplane) is given as a possible implementation of a reversible function, *as an exercise for the student*. All examples shown use XOR. Does anyone have a copy of the 1973 edition? Does it also have this material? Our library only has the 2nd edition. -- Peter Lamb uucp: uunet!mcsun!ethz!prl eunet: prl@iis.ethz.ch Tel: +411 256 5241 Integrated Systems Laboratory ETH-Zentrum, 8092 Zurich
baxter@ics.uci.edu (Ira Baxter) (06/27/90)
In <4899@ethz.UUCP> prl@ethz.UUCP (Peter Lamb) writes: >In article <1990Jun26.182359.2989@utzoo.uucp>, henry@utzoo.uucp (Henry Spencer) writes: >> In article <555@dg.dg.com> mpogue@dg.dg.com writes: >> > I think all it takes is an example of a commercially shipped system, >> >that can be shown to have used the XOR technique, before the claimed date >> >of Cadtrak's invention. >> >> Independent invention, even prior independent invention, does not necessarily >> invalidate a patent. Prior *publication* generally does, as it is presumed >> to make the idea well-known, but a handful of highly-proprietary systems >> shipped earlier might not qualify. >Newmann and Sproull talk about the use of reversible raster operations >for cursors in `Introduction to Computer Graphics'. The earliest copy I >have is 1979 (2nd edition), but there's a 1973 copyright (to McGraw-Hill) >in the cover sheets. This is presumabably the first edition. >The use of arithmetic modulo 2^n (ie XOR for one bitplane) is given >as a possible implementation of a reversible function, *as an exercise >for the student*. All examples shown use XOR. >Does anyone have a copy of the 1973 edition? Does it also have >this material? Our library only has the 2nd edition. I do. Raster ops aren't mentioned :-{ On the other hand, if N&S put it into the 1979 edition, presumably there are technical articles in which it was documented before it appeared in N&S; their bibliography in the 1973 version is pretty extensive, so I would expect a reference to such a technical article in the 1979 version. I don't have the 1979 version, so I can't check this. Another place to look is obviously in Foley& van Dam, "Fundamentals of Computer Graphics", who also have an extensive bibliography. -- Ira Baxter
henry@utzoo.uucp (Henry Spencer) (06/27/90)
In article <4899@ethz.UUCP> prl@ethz.UUCP (Peter Lamb) writes: >Newmann and Sproull talk about the use of reversible raster operations >for cursors in `Introduction to Computer Graphics'. The earliest copy I >have is 1979 (2nd edition), but there's a 1973 copyright (to McGraw-Hill) >in the cover sheets. This is presumabably the first edition. >... >Does anyone have a copy of the 1973 edition? Does it also have >this material? Our library only has the 2nd edition. My copy of the 1973 edition is around somewhere, but not handy. Alas, it had very little on frame-buffer algorithms, because useful frame buffers were not very common then. If memory serves, all the stuff on RasterOp etc. was added in the second edition. -- "Either NFS must be scrapped or NFS | Henry Spencer at U of Toronto Zoology must be changed." -John Osterhout | henry@zoo.toronto.edu utzoo!henry
uad1077@dircon.uucp (06/28/90)
Hmmmm. Cadtrak have a patent on XORing cursors into framebuffers. Quantel (the PaintBox people) have a patent on read-modify-write cycles into framebuffers - and they are just as ugly about enforcing it. :-) Perhaps we should tell their lawyers about each other and stand back?? With luck, the two companies will annihilate each other :-) -- Ian D. Kemmish Tel. +44 767 601 361 18 Durham Close uad1077@dircon.UUCP Biggleswade ukc!dircon!uad1077 Beds SG18 8HZ United Kingd uad1077%dircon@ukc.ac.uk