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README file for xearth, version 1.1 Kirk Lauritz Johnson <firstname.lastname@example.org> 6 November 1999 WHAT IS IT? Xearth sets the X root window to an image of the Earth, as seen from your favorite vantage point in space, correctly shaded for the current position of the Sun. By default, xearth updates the displayed image every five minutes; the time between updates can be changed using either X resources or a command line option. Xearth can also be configured to render into a top-level X window or directly into PPM and GIF files; see the man page for details. See the HISTORY file for a list of changes since earlier versions of xearth. WHERE TO GET IT? The latest-and-greatest version of xearth should always be available via a link from the xearth WWW home page (URL http://www.cs.colorado.edu/~tuna/xearth/index.html), or, for the web-deprived, via anonymous ftp from cag.lcs.mit.edu in /pub/tuna. NOTES If you are trying to build xearth under SunOS 4.x using /bin/cc, make sure to read the section of the INSTALL file entitled "BUILDING UNDER SUNOS 4.x" regarding a compiler bug. The map information used in xearth was derived from the "CIA World Data Bank II map database," as taken from some "cbd" files that were apparently originally generated by Brian Reid at DEC WRL. Running in the background on 350 MHz Pentium II, xearth requires less than one CPU second each time it redraws an image in the root window. With the default time-between-redraws of 300 seconds, I simply don't notice the extra CPU load. Your mileage may vary, of course, especially on slower machines. The Graphics Interchange Format(c) is the Copyright property of CompuServe Incorporated. GIF(sm) is a Service Mark property of CompuServe Incorporated. Thanks to Robert Berger for allowing me to include his nifty Gamma Measurement Image and associated text in the xearth source distribution. Thanks to Jamie Zawinski for suggesting that I look at his xscreensaver package for a good example of how to use the resource and command line option parts of Xt; his code saved me piles of lossage. Thanks to Chris Metcalf for the -bigstars stuff, a pile of general source code cleaning, and spell checking everything carefully. Thanks to Chris Hayward, Chris Metcalf, Sherman Mui, Dan Rich, and Leonard Zubkoff for giving the pre-release of version 1.0 a test drive. Kudos to Jef Poskanzer for his excellent PBMPLUS toolkit. Finally, thanks to everybody that sent encouragement, suggestions, and patches. Apologies to the many people whose good ideas didn't make it into this release. IDEAS FOR FUTURE WORK Better error recovery (better than "assert()", anyway). Add options/resources that specify colors other than the default green, blue, red, white, and black. Code for tracking real-life orbits ("-pos hubble"). Support for supersampling/antialiasing. AUTHOR Kirk Johnson <email@example.com> Patches, bug reports, and suggestions are welcome, although I can't guarantee that I'll get around to doing anything about them in a timely fashion. LEGAL STUFF Copyright (C) 1989, 1990, 1993-1995, 1999 Kirk Lauritz Johnson Parts of the source code (as marked) are: Copyright (C) 1989, 1990, 1991 by Jim Frost Copyright (C) 1992 by Jamie Zawinski <firstname.lastname@example.org> Permission to use, copy, modify and freely distribute xearth for non-commercial and not-for-profit purposes is hereby granted without fee, provided that both the above copyright notice and this permission notice appear in all copies and in supporting documentation. Unisys Corporation holds worldwide patent rights on the Lempel Zev Welch (LZW) compression technique employed in the CompuServe GIF image file format as well as in other formats. Unisys has made it clear, however, that it does not require licensing or fees to be paid for freely distributed, non-commercial applications (such as xearth) that employ LZW/GIF technology. Those wishing further information about licensing the LZW patent should contact Unisys directly at (email@example.com) or by writing to Unisys Corporation Welch Licensing Department M/S-C1SW19 P.O. Box 500 Blue Bell, PA 19424 The author makes no representations about the suitability of this software for any purpose. It is provided "as is" without express or implied warranty. THE AUTHOR DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.