NAME
rholo - generate/view a RADIANCE holodeck
SYNOPSIS
rholo [ -n npr ][ -o dev ][ -w ][ -i ][ -f | -r ] hdkfile [ varfile | +
| - [ VAR=value .. ] ]
DESCRIPTION
Rholo is a program for generating and viewing holodeck files. Similar
to rvu(1), rholo can compute views interactively, but unlike rvu, it
reuses any and all information that was previously computed in this or
earlier runs using the given holodeck file, hdkfile.
The -n option sets the number of rtrace(1) processes to start for the
calculation. It defaults to zero, which means that no new rays will be
calculated. In general, it is unwise to start more processes than
there are processors on the system. On a multiprocessing system with 4
or more processors, a value one less than the total should yield
optimal interactive rates on a lightly loaded system.
The -o option sets the output device to use for display. Currently,
there are at least two display drivers available, x11 and glx. If no
output device is specified, then rholo will start a global calculation
of the holodeck, filling it in as time goes by. The quality of the
final holodeck will depend on how long rholo runs before it is
interrupted or runs out of file space or time, according to the
variable settings described in the control variable section, below. If
no output device and no processes are specified, rholo creates an empty
holodeck using the given varfile, if present.
The -i option provides for reading from the standard input. Without a
display driver, the input should consist only of views, which will be
used to limit which parts of the holodeck are rendered in a batch
calculation. With a display driver, most of the commands understood by
the driver can be issued either from the operating window or the
standard input. These commands are described together with their
window equivalents in the display driver section following the control
variable section.
The -f option permits the given holodeck to be clobbered. Without this
option, giving both the holodeck file and a variable file (or "-") will
result in an error message if the holodeck exists, since giving both
implies that a new holodeck is being created. (When reusing an
existing holodeck, the variable values are taken from the holodeck
header, though some may be overriden by giving a "+" in place of the
variable file.) Also, attempts to clear the holodeck using the
interactive "clobber" command will be permitted only if the -f option
is given on the initial command line.
The -r option tells rholo to open the holodeck file read-only, which is
the default if there are no ray calculation processes. If one or more
rtrace processes are started with the -n option and the -r option is
given or the specified holodeck is not writable by the user, then any
additional rays computed during the session will be discarded rather
than saved to the holodeck file.
One or more holodeck section boundaries are defined along with other
parameters in the holodeck file or, if the holodeck is being created,
the rholo control variable file, varfile. These section boundaries
define where you may move, or at least, where you will be able to see,
since they determine where computed rays are stored. Additional
variable settings may be added or overridden on the command line
following varfile. If no varfile is needed, a holodeck may still be
created by giving a "-" on the command line in place of the variable
file. If you wish to override some of the variable settings in an
existing holodeck, use a "+", followed by the new settings on the
command line. Upper case variables specified more than once will
result in a warning message (unless the -w option is present), and the
last value given will be the one used, unless it would conflict with
something in an existing holodeck that cannot be changed, such as the
section boundaries. Changing section boundaries requires creating a
new holodeck using rholo without a -n or -o option, then running
rhcopy(1) to fill the new holodeck with the old holodeck’s contents.
The -w option turns off warnings about multiply and misassigned
variables.
Rendering variable assignments appear one per line in varfile. The
name of the variable is followed by an equals sign (’=’) and its
value(s). The end of line may be escaped with a backslash (’\’),
though it is not usually necessary. Variables that should have only
one value are given in upper case. Variables that may have multiple
values are given in lower case. Variables may be abbreviated by their
first three letters. Comments in varfile start with a pound sign (’#’)
and proceed to the end of line.
CONTROL VARIABLES
The control variables, their interpretations and default values are
given below.
OCTREE The name of the octree file. The default name is the same as
hdkfile but with any suffix replaced by ".oct". This
variable may also be read from rad(1) if the "RIF" variable
is set. (See below.)
RIF This variable specifies a rad input file to use as a source
of rendering options and other variable settings. If given,
rholo will execute rad and get the rendering options to later
pass to rtrace. Besides prepending the render variable,
rholo will also extract default settings for the common
"OCTREE" variable, and the "EYESEP" variable. Following the
file name, overriding variable settings may be given, which
will be passed to rad on the command line. Settings with
spaces in them should be enclosed in quotes. The execution
of rad will also update the contents of the octree, if
necessary. There is no default value for this variable.
EYESEP The interocular spacing for stereo viewing. I.e., the world
distance between the pupils of the left and right eyes.
There is no default value for this variable.
section A section is a 6-sided parallel prism given by an origin and
three axis vectors (i.e., 12 floating point values in world
coordinates). The axis vectors define the three edges
attached to the origin vertex, and the other edges and
vertices are determined by the parallel wall constraint. A
holodeck section is a region in which the user may freely
move about to obtain a view of what is outside that region.
In object rendering mode, a section may instead contain a
detailed object to be viewed from the outside. The grid
dimensions for each axis may also be given by three
additional integer arguments following the prism axes.
Otherwise, if the grid dimensions are left out or any are
unspecified or zero, the "GRID" variable will be used to
determine them from the section axis lengths. (See below.)
There is no default value for this variable, and it is
required. If multiple values are given, they will be used
for multiple rendering sections, which may or may not be
connected, but should generally not overlap. The starting
view for interactive display will be the center of the first
section facing the positive X direction unless "OBSTRUCTIONS"
is set to True, when the view will be placed outside the
first section. (See below for this variable’s definition.)
The third axis of the first section is also used as the
default "view up" vector.
geometry This variable is used to associate geometry from an octree
file with one or more sections. The specified octree will be
used by certain drivers (e.g., the "ogl" driver) to display
simplified geometry using hardware lighting during motion.
If this variable is not set, such drivers will use the main
octree file, which contains all the scene geometry. This can
be slow if the scene is complex, so use simplified geometry
with portals (described below) or specify a non-existent file
to turn geometry rendering off. If there is just one setting
of this variable, it will be used for all sections. If there
are multiple settings, they will correspond to multiple
sections.
portals This variable is used to associate portal geometry with one
or more sections, as required for simplified geometry in some
drivers (e.g., "ogl"). The portal geometry itself is given
in one or more RADIANCE scene files or quoted commands
beginning with an exclamation mark (’!’), and the input may
or may not include material definitons. (I.e., the surfaces
may be modified by "void" if there are no materials.) A
portal is an imaginary surface that intervenes between a view
and some detailed geometry not included in the current
section. (See the "geometry" variable definition, above.)
Portals are often placed in doorways, windows and in front of
mirrors. Portal geometry may also be placed around local
geometry that has been culled due to its complexity. This
specification is necessary in order that the detail geometry
be drawn correctly, and that mirrors will work with virtual
distances. (See the definition of "VDISTANCE," below.) The
orientation of the portal surface geometry is ignored, so
they have effect no matter which way they are facing. If
there is just one setting of this variable, it will be used
for all sections. If there are multiple settings, they will
correspond to multiple sections.
GRID The default section grid size in world distance units. If
any section axis grid is unspecified, the length of the axis
will be divided by this number and rounded up to the next
larger integer. The grid size is a very important determiner
of holodeck performance, since the holodeck beam index is
proportional to average axis grid dimension to the fourth
power! If the beam index is too large, poor file and memory
performance will result. If the beam index is too small, the
holodeck resolution will suffer and objects will tend to
break up. In general, the grid size should divide each
section wall into 64 or fewer cells for optimal performance.
The default value for this variable is the maximum section
axis length divided by 8.
OBSTRUCTIONS
This boolean variable tells rholo whether or not to compute
intersections with objects inside holodeck sections. If it
is set to "False", then only objects outside the holodeck
sections will be visible. This is appropriate when you know
all sections to be devoid of geometry, or when some secondary
method is available for rendering geometry inside each
section. If it is set to "True," all inside geometry will be
visible. There is no default for this variable, which means
that rays will be started at random points within each
holodeck section, allowing interior geometry to be partially
sampled.
VDISTANCE This boolean variable determines whether the actual distance
to objects is computed, or the virtual distance. If it is
set to "True," the virtual distance will be used, which will
make reflections and refractions through smooth, flat objects
clear, but will blur the boundaries of those objects. Note
that some drivers cannot render virtual samples without the
proper placement of "portals" in the scene. (See above for
the definition of the "portals" variable.) If it is set to
"False," the reflections and refractions will be blurred, but
object boundaries will remain sharp. The default value for
this variable is "False."
CACHE The memory cache size to use for ray samples during
interactive rendering, in Megabytes. This tuning parameter
determines the tradeoff between memory use and disk access
time for interactive display. This value will not affect
memory use or performance for global holodeck rendering if
there is no display process. The default cache is
effectively set to 16 Megabytes. If this variable is set to
zero, no limit will be placed on memory use and the process
will grow to accommodate all the beams that have been
accessed.
DISKSPACE Specifies the maximum holodeck file size, in Megabytes. Once
the holodeck file reaches this size, rtrace will exit. If
there is no display process, rholo will also exit. The
default value for this variable is 0, which is interpreted as
no size limit.
TIME Sets the maximum time to run rtrace, in decimal hours. After
this length of time, rtrace will exit. If there is no
display process, rholo will also exit. If there is a display
process, and rtrace is restarted with the "restart" command,
then the time clock will be restarted as well. The default
value for this variable is 0, which is interpreted as no time
limit.
REPORT This variable may be used to specify a interval for progress
reports in minutes. If this value is zero, then progress
reports will not be given in intervals, but a final report of
the file size and fragmentation will be issued when the
program terminates, along with the number of rays and packets
computed. If a filename is given after the interval, it will
be used as the error file for reports and error messages
instead of the standard error. There is no default value for
this variable.
render This variable may be used to specify additional options to
rtrace. These options will appear after the options set
automatically by rad, and thus will override the default
values.
DISPLAY DRIVER
Rholo may be started in interactive mode using the -o option to specify
an output display driver. Currently, three drivers are supported on
most machines, glx, ogl and x11. (In addition, there are variations on
the first two drivers for stereo displays, local objects and human tone
mapping. These are accessed with some combination of the ’s’, ’o’ and
’h’ suffixes, always in that order. E.g., the OpenGL stereo driver
with human tone mapping would be "oglsh".) Each driver accepts simple
one-character commands and mouse view control in its operating window.
If the -i option is also given, then the driver will also listen for
commands entered on the standard input. (It is unwise to use the -i
option when rholo is run in the background, because it will
occassionally stop the process when input is available on the
controlling terminal.) The commands and their single-key window
equivalents are given below.
VIEW= (mouse)
Modify the current view with the specified parameters. (See
the -v* view options in the rpict(1) manual page for
parameter details.) There is no one-character equivalent for
this command in the display window. Instead, the mouse is
used to control the current view in the following ways:
CONTROL MOUSE ACTION
(none) left Move forward towards cursor position
(none) middle Rotate in place (usually safe)
(none) right Move backward away from cursor position
shift left Orbit left around cursor position
shift middle Orbit skyward
cntl middle Orbit earthward
shift right Orbit right around cursor position
cntl+shift any Frame focus by dragging rectangle
For all movements but rotating in place, the cursor must be
placed over some bit of visible geometry, otherwise the
driver has no reference point from which to work. It is best
to just experiment with these controls until you learn to fly
safely in your model. And if you run into trouble, the
"last" command is very useful. (See below.)
last ’l’
Return to the previous view. Some drivers will save up
multiple views in a history, but you are guaranteed at least
one.
where ’v’
Print the current view parameters to the standard output.
This is useful for finding out where you are, or for saving
specific views in a keyframe file for animations or returning
to later.
frame ’f’
Change the calculation focus. If the "frame" command is
given with no arguments on the standard input, it is
equivalent to the interactive ’F’ command, which releases the
current calculation focus. If the "frame" command is
followed by a relative horizontal and vertical position
(specified as floating point values between 0 and 1), then
the new focus is about this position on the screen (where 0 0
is at the lower left of the display). This is equivalent to
the interactive ’f’ command, which sets the focus about the
current window cursor position. If four relative coordinates
are given, they are assumed to mean the minimum horizontal
and vertical positon, and the maximum horizontal and vertical
position, in that order. This is equivalent to dragging the
mouse over a rectangular area with the ’cntl+shift’ keys held
down.
pause ’p’
Pause the ray calculation temporarily.
resume <cr>
Resume the ray calculation.
redraw ^L
Redraw the current view from values calculated and stored in
the holodeck. When executed from the display window via
’^L’, the effect may be slightly different, since all stored
information will be flushed.
kill ’K’
Terminate the ray calculation process. This is usually
unnecessary, but is provided for special purpose
applications.
restart ’R’
Restart the ray calculation process. If the "RIF" variable
has been set, rad will be run first to assure that the octree
is up to date.
clobber ’C’
Clobber the holodeck contents, deleting all that has been
calculated before. To get an interactive dissolve of changes
to the scene description, use the sequence "kill," "clobber,"
"restart." This command will be honored by rholo only if it
was started with the -f option.
quit ’q’
Quit rholo. The ray tracing calculation is terminated and
all values are flushed to the holodeck file. This is the
normal way to exit the program.
In addition to these standard commands, all drivers offer the following
supplimentary controls.
’h’ Fix the head height. All mouse-controlled view motions will
be adjusted so that the head height does not change (where
vertical is determined by the current view up vector).
’H’ Release the head height, allowing it to change again during
mouse-controlled movements.
^R Redraw the current view, recomputing the tone mapping in the
process. This is useful if the current view is too light or
too dark. (On an 8-bit display, it may be necessary to
redraw the screen a couple of times to get the best image.)
The "^L" command is a stronger type of redraw, since it will
use only rays in the current view to determine the tone
mapping, rather than a history of rays drawn from the rholo
server.
EXAMPLES
The following shows a minimal holodeck control variable file:
RIF= sample.rif # rad input file
section= 2 2 4 5 0 0 0 7 0 0 0 3 # section prism boundaries
Technically, the "RIF" setting is not necessary, but the results are
much better when rholo is used in association with rad to control the
rendering parameters.
Here is a slightly more sophisticated example:
RIF=electric.rif
section= 7 4 3.5 15 0 0 0 10 0 0 0 5
GRID= .75
CACHE= 20 # cache size in megabytes
TIME= 120 # maximum time in hours
DISK= 200 # maximum file size in megabytes
REPORT= 60 elect.her
OBST= False
VDIST= False
We can invoke rholo on the above file to compute a hologram overnight
in batch mode:
rholo -n 1 elect.hdk elect.hif TIME=12 &
This will report progress every hour to "elect.her".
The next morning, we can look at the holodeck interactively:
rholo-n 1 -o x11 elect.hdk &
If the previous command were still running, the above command would
fail because the permissions on the holodeck would not grant access.
To terminate rholo without losing any computed information, use the
kill(1) command to send an interrupt or terminate signal to the rholo
process listed by ps(1). If the system goes down or something dire
happens to rholo, it may be necessary to restore read/write permission
on the holodeck using chmod(1). Do not do this, however, unless you
are absolutely sure that rholo is no longer running on the holodeck.
(See the ps man page on how to check for running processes. The file
modification date as reported by ls(1) is another clue.)
To view the holodeck without invoking a new ray calculation, leave off
the -n option. To compute the holodeck with multiple processes on a
multiprocessing system, use a higher number for the -n option. (Don’t
use more processes than you have processors, though, because you’ll
only slow things down.)
To allow interactive control of rholo from another process, the
following invocation will override the file size limit and permit the
holodeck to be clobbered by a command entered on the standard input:
rholo -n 1 -o x11 -i -f elect.hdk + DISK=0
To create an empty holodeck from settings on the command line:
rholo new.hdk - RIF=sample.rif "section=2 2 4 8 0 0 0 10 0 0 0 3"
NOTES
Each time rays are added to a beam, that beam’s position in the
holodeck file is released and a new position is found. After
substantial computation on a holodeck, especially over several runs,
the holodeck file may become fragmented, leaving holes that take up
space without contributing useful information. The percentage
fragmentation is reported when the REPORT variable is set and some
calculation has taken place. When this percentage gets high on a large
holodeck (above 15% or so), it is a good idea to run the rhoptimize(1)
program once batch rendering is complete to close the gaps and collect
beams into groups for quicker rendering access. Rholo will print
periodic warnings when the fragmentation exceeds 20%.
AUTHOR
Greg Ward Larson
ACKNOWLEDGMENT
This work was supported by Silicon Graphics, Inc.
BUGS
Global participating media are not handled correctly, though local
participating media will usually work.
SEE ALSO
chmod(1), ls(1), ps(1), rad(1), ranimate(1), rhcopy(1), rhinfo(1),
rhoptimize(1), rhpict(1), rpict(1), rtrace(1), rvu(1)