xpgs(6) Xpgs 2.5 xpgs(6)
November 1994
NAME
xpgs - a suite of programs to design, generate and animate SIRDS for
the X Window System, and output SIS or autostereograms in a variety of
formats
SYNTAX
xpgs [options] <polyh or xss file>
OVERVIEW
SIRDS stands for Single-Image Random Dots Stereogram; other common
terms are RDS, SIS and autostereograms though these do not strictly
apply to, or imply, SIRDS.
The theory of SIRDS and autostereograms can be found in many postings
to alt.3d (including a FAQ obtainable from
http://www.cs.waikato.ac.nz/~singlis/sirds.html) and comp.graphics,
there are also some books around which deal with the subject. Some
information can be obtained on RDS from Bela Julesz's book
"Foundations of Cyclopean Perceptions"; a more recent source of
information is the paper by Thimbleby et al called "Displaying 3D
images: Algorithms for SIRDS", available from Stuart Inglis
(singlis@waikato.ac.nz); also there is a short article called
"Stereography and Autostereograms" by the author of this package which
can be found, along with a gallery and URL links to other WWW pages on
SIRDS, at http://h2.ph.man.ac.uk/gareth/sirds.html. Further resources
can be found at the main SIRDS at
ftp://katz.anu.edu.au/pub/stereograms/.
In this suite of programs, we start with a description of a volume of
space using Cartesian coordinates to label the vertices of the objects
within the space and lists of the polygonal faces which define each
object. The coordinate axes are defined as x - horizontal (right), y
- vertical (upward) and z - perpendicular to the screen (toward the
viewer).
With this description, two buffers are built using a method described
in the article mentioned above.
There are two basic types of autostereograms, these differ in the way
the image is viewed. The two possibilities are wide-eyed (WE) and
cross-eyed (CE) viewing. For whatever reasons, some people find it
much easier to look at SIRDS cross-eyed though the vast majority learn
to see them wide-eyed.
The parameters of the programs are :-
VD = viewing distance from the screen or paper (300mm)
ES = eye separation (65mm)
(150mm)
OS = offset of coordinate origin into (or out of) screen or paper
The background plane is set at the offset OS+OY, this can be changed
with the -background option.
(c)1994 by Peter Chang - 1 - xpgs 2.5
xpgs(6) Xpgs 2.5 xpgs(6)
November 1994
The default options are set to give a reasonable wide-eyed (WE) SIRDS
of the objects on top of a background plane.
STRUCTURE
A layout of the suite's programs and associated data follows
3d datasets
|
|
v
cvtopolyh mkpolyh
| |
| |
| |
/-------------------------\ paint package
| | | ^
| (.polyh) | (.polyh) | | (.p?m)
| | | |
v v v v
xss --------> xpgs -------> cvtoppm <------ mindimage
| (.xss) | | | (.rle)
| | (.p?m) | |
| | v |
\-------------------> sisgen \----------> vpgs
(.xss) | (.p?m)
|
|
v
xv
MindImage is a PC SIRDS generator, xv is the X11 graphics viewer. The
data files are differentiated by their name extensions given in
parentheses. Although not shown on the diagram, xss, vpgs and xpgs
can save an image in X11 bitmap (.xbm) format and vpgs and xpgs can
also save an image as a Postscript (.ps) file.
DATA FILES
.polyh We have incorporated one 3D data format into xpgs:
AVS polyh - list of vertices and list of polygonal faces
given by indexed points.
(There is a slight difference with the inclusion of an
optional comment line at the start of the file which begins
with a hash "#".)
Additional objects can be converted into this format using the
cvtopolyh program, it is able to change X3d v2.0 .obj files,
Wavefront .obj files and another format .3ds (I can't remember
what program uses this). New objects defined by functions can
(c)1994 by Peter Chang - 2 - xpgs 2.5
xpgs(6) Xpgs 2.5 xpgs(6)
November 1994
be made using mkpolyh.
We have bundled some objects for you to try out - regular
solids in polyh format and a couple of objects converted from
X3d v2.0 objects and Wavefront objects.
More objects can be found at ftp://avalon.chinalake.navy.mil/
or its mirrors.
.rle This is MindImage's data format using a basic run length
encoding method with indexing.
.p?m = .ppm and .pgm
These are the colour and grey-scale portable pixmap formats
from the PBM packages (NetPBM or PBMPlus).
.xss This is a simple description format of a scene made from
multiple polyh objects.
DESCRIPTION
Xpgs is an X11 program that generates, animates and outputs SIRDS. It
takes an .xss or a .polyh file and optional switches as its command
line arguments.
Options
All these options can be abbreviated to the least letters needed to
make the chosen option distinct. The default values are given in
parentheses.
-display <display>
sets the X display name. By default it is the local host or that
one defined in the environment variable DISPLAY.
-geometry <geometry>
sets the X geometry. (770x476 or 720x445)
-wait <delay>
specifies the delay between frames in milliseconds used during
animation. (300)
-frames <1-24>
gives the number of frames for xpgs to generate. (1)
If xpgs was compiled with the XPGSUSEPM macro defined then the
number of frames of animation possible depends on the X server
memory allocation, ie. the number of big Pixmaps it can support.
If your server can't handle a large number then either give xpgs a
smaller number of frames, eg. "-f 3", or recompile xpgs without
the -DXPGSUSEPM flag in the Makefile (make.com or descrip.mms).
Note if you take the latter option then the animation may not be
as fast as using Pixmaps, the performance depends on the X server.
(c)1994 by Peter Chang - 3 - xpgs 2.5
xpgs(6) Xpgs 2.5 xpgs(6)
November 1994
-background <b>
sets the background plane at z=b*OY. (-1.0)
-reverse
sets xpgs to cater for crosseyed viewing, by default it caters for
wide-eyed viewing.
-enlarge <ef>
specifies the enlargement of depth effect in the final image.
(1.0)
-mag <mf>
sets the magnification of the scene. (1.0)
-paper <wxh>
specifies the size of array for Postscript output.
-indicoff
turns off indicators in window (used to aid the viewing process).
-zblines <zb>
sets the number of lines that each z-buffer will use. (256)
This limits the internal size of all z-buffers used in the program
without affecting the size of the stereogram output. It should be
used only when memory constraints are more important than speed
considerations: the smaller the value is the slower the program
will become.
-DENSITY <0-255>
sets the density of black dots in the SIRDS. (127)
-GREY <1,2,4,8>
sets the number of grey-scale bits used in Postscript output. (1)
-SHIMMER
sets xpgs to the shimmer mode, to aid newbies.
-help
prints a summary of command line options and returns to shell.
Once running, it will display a few parameters in the terminal window,
create a empty graphics window and start to generate the SIRDS(s).
Each frame will be shown in sequence as the program proceeds. When
finished, the program displays the "all done" message and enters the
pause mode.
KEYS
With the mouse pointer within the boundaries of the graphics window,
xpgs will respond to a set of keypresses.
(c)1994 by Peter Chang - 4 - xpgs 2.5
xpgs(6) Xpgs 2.5 xpgs(6)
November 1994
q quits the program.
h pops up a help window.
a changes the rotation axis randomly.
i re-initialise all of the points.
p toggles the pause mode on and off.
r reverses the sequence of frames.
While paused:
c saves the current frame in .xss format.
l loads a new object.
n skips to the next frame.
s saves the current frame as a Postscript file.
w saves the current frame as a X11 bitmap.
See xss(6) about mouse controls and popup dialogue windows.
FILES
BUGS
If you find any bugs, please report them to one of the authors listed
below.
SEE ALSO
cvtopolyh(6), cvtoppm(6), mkpolyh(6), sisgen(6), vpgs(6), xpgs(6) and
xss(6).
AUTHORS, COPYRIGHTS, AND WARNINGS
Copyright 1994, 16th November and 14th February.
By Peter Chang and Gareth Richards. All rights reserved.
peterc@v2.ph.man.ac.uk
gareth@h1.ph.man.ac.uk
Version 2.5
Permission to use, copy, modify, distribute, and sell this software
and its documentation for any purpose is hereby granted without fee,
provided that the above copyright notice appear in all copies and that
both that copyright notice and this permission notice appear in
supporting documentation, and that the name of the copyright holder
not be used in advertising or publicity pertaining to distribution of
the software without specific, written prior permission. The copyright
holder makes no representations about the suitability of this software
for any purpose. It is provided "as is" without express or implied
warranty.
The copyright holder disclaims all warranties with regard to this
software, including all implied warranties of merchantability and
fitness, in no event shall the copyright holder 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.
(c)1994 by Peter Chang - 5 - xpgs 2.5
