XScreenSaver(1)

NAME
       penrose - draws quasiperiodic tilings

SYNOPSIS
       penrose [-display host:display.screen] [-foreground color]
       [-background color] [-window] [-root]  [-mono]  [-install]
       [-visual  visual] [-ncolors integer] [-delay microseconds]
       [-size integer] [-ammann] [-no-ammann]

DESCRIPTION
       The penrose program draws quasiperiodic tilings.

       See Onoda, Steinhardt, DiVincenzo  and  Socolar  in  Phys.
       Rev.  Lett.  60,  #25,  1988 or Strandburg in Computers in
       Physics, Sep/Oct 1991.

       This implementation uses the simpler version of the growth
       algorithm,  i.e.,  if there are no forced vertices, a ran-
       domly chosen tile is added to a randomly chosen vertex (no
       preference for those 108 degree angles).

       There  are two essential differences to the algorithm pre-
       sented in the literature:  First,  we  do  not  allow  the
       tiling  to  enclose  an untiled area.  Whenever this is in
       danger of happening, we just do not add the  tile,  hoping
       for  a  better  random choice the next time.  Second, when
       choosing a vertex randomly, we will  take  one  that  lies
       withing the viewport if available.  If this seems to cause
       enclosures in the forced rule case, we will allow  invisi-
       ble vertices to be chosen.

       Tiling is restarted whenever one of the following happens:
       there are no incomplete vertices within  the  viewport  or
       the  tiling has extended a window's length beyond the edge
       of the window horizontally or vertically  or  forced  rule
       choice  has  failed 100 times due to areas about to become
       enclosed.

OPTIONS
       penrose accepts the following options:

       -window Draw on  a  newly-created  window.   This  is  the
               default.

       -root   Draw on the root window.

       -mono   If   on  a  color  display,  pretend  we're  on  a
               monochrome display.

       -install
               Install a private colormap for the window.

       -visual visual
               Specify which visual to use.  Legal values are the
               name  of a visual class, or the id number (decimal
               or hex) of a specific visual.

       -ncolors integer
               How many colors  should  be  used  (if  possible).
               Default 64.  The colors are chosen randomly.

       -size integer
               How big the tiles should be.  Default 40 pixels.

       -ammann integer

       -no-ammann integer
               Whether Ammann lines should be added.

ENVIRONMENT
       DISPLAY to get the default host and display number.

       XENVIRONMENT
               to  get the name of a resource file that overrides
               the global resources stored in  the  RESOURCE_MAN-
               AGER property.

SEE ALSO
       X(1) xscreensaver(1) xlock(1) 

COPYRIGHT
       Copyright (C) 1996 by Timo Korvola.

       Permission to use, copy, modify, and distribute this soft-
       ware and its documentation for any purpose and without fee
       is  hereby  granted,  provided  that  the  above copyright
       notice appear in all copies and that both  that  copyright
       notice  and  this  permission  notice appear in supporting
       documentation.

AUTHOR
       Timo Korvola lt;tkorvola@dopey.hut.fi, 1996.

       Ability to run standalone or with  xscreensaver  added  by
       Jamie Zawinski lt;jwz@netscape.com, 10-May-97.