NAME
rpict - generate a RADIANCE picture
SYNOPSIS
rpict [ options ] [ $EVAR ] [ @file ] [ octree ]
rpict [ options ] -defaults
DESCRIPTION
Rpict generates a picture from the RADIANCE scene given in octree and
sends it to the standard output. If no octree is given, the standard
input is read. (The octree may also be specified as the output of a
command enclosed in quotes and preceded by a ‘!’.) Options specify the
viewing parameters as well as giving some control over the calculation.
Options may be given on the command line and/or read from the
environment and/or read from a file. A command argument beginning with
a dollar sign (’$’) is immediately replaced by the contents of the
given environment variable. A command argument beginning with an at
sign (’@’) is immediately replaced by the contents of the given file.
In the second form shown above, the default values for the options
(modified by those options present) are printed with a brief
explanation.
Most options are followed by one or more arguments, which must be
separated from the option and each other by white space. The
exceptions to this rule are the -vt option and the boolean options.
Normally, the appearance of a boolean option causes a feature to be
"toggled", that is switched from off to on or on to off depending on
its previous state. Boolean options may also be set explicitly by
following them immediately with a ’+’ or ’-’, meaning on or off,
respectively. Synonyms for ’+’ are any of the characters "yYtT1", and
synonyms for ’-’ are any of the characters "nNfF0". All other
characters will generate an error.
-vtt Set view type to t. If t is ’v’, a perspective view is
selected. If t is ’l’, a parallel view is used. A
cylindrical panorma may be selected by setting t to the
letter ’c’. This view is like a standard perspective
vertically, but projected on a cylinder horizontally (like a
soupcan’s-eye view). Three fisheye views are provided as
well; ’h’ yields a hemispherical fisheye view, ’a’ results in
angular fisheye distortion, and ’s’ results in a planisphere
(stereographic) projection. A hemispherical fisheye is a
projection of the hemisphere onto a circle. The maximum view
angle for this type is 180 degrees. An angular fisheye view
is defined such that distance from the center of the image is
proportional to the angle from the central view direction.
An angular fisheye can display a full 360 degrees. A
planisphere fisheye view maintains angular relationships
between lines, and is commonly used for sun path analysis.
This is more commonly known as a "stereographic projection,"
but we avoid the term here so as not to confuse it with a
stereoscopic pair. A planisphere fisheye can display up to
(but not including) 360 degrees, although distortion becomes
extreme as this limit is approached. Note that there is no
space between the view type option and its single letter
argument.
-vp x y z Set the view point to x y z . This is the focal point of a
perspective view or the center of a parallel projection.
-vd xd yd zd
Set the view direction vector to xd yd zd . The length of
this vector indicates the focal distance as needed by the -pd
option, described below.
-vu xd yd zd
Set the view up vector (vertical direction) to xd yd zd .
-vh val Set the view horizontal size to val. For a perspective
projection (including fisheye views), val is the horizontal
field of view (in degrees). For a parallel projection, val
is the view width in world coordinates.
-vv val Set the view vertical size to val.
-vo val Set the view fore clipping plane at a distance of val from
the view point. The plane will be perpendicular to the view
direction for perspective and parallel view types. For
fisheye view types, the clipping plane is actually a clipping
sphere, centered on the view point with radius val. Objects
in front of this imaginary surface will not be visible. This
may be useful for seeing through walls (to get a longer
perspective from an exterior view point) or for incremental
rendering. A value of zero implies no foreground clipping.
A negative value produces some interesting effects, since it
creates an inverted image for objects behind the viewpoint.
This possibility is provided mostly for the purpose of
rendering stereographic holograms.
-va val Set the view aft clipping plane at a distance of val from the
view point. Like the view fore plane, it will be
perpendicular to the view direction for perspective and
parallel view types. For fisheye view types, the clipping
plane is actually a clipping sphere, centered on the view
point with radius val. Objects behind this imaginary surface
will not be visible. A value of zero means no aft clipping,
and is the only way to see infinitely distant objects such as
the sky.
-vs val Set the view shift to val. This is the amount the actual
image will be shifted to the right of the specified view.
This is option is useful for generating skewed perspectives
or rendering an image a piece at a time. A value of 1 means
that the rendered image starts just to the right of the
normal view. A value of -1 would be to the left. Larger or
fractional values are permitted as well.
-vl val Set the view lift to val. This is the amount the actual
image will be lifted up from the specified view, similar to
the -vs option.
-vf file Get view parameters from file, which may be a picture or a
file created by rvu (with the "view" command).
-x res Set the maximum x resolution to res.
-y res Set the maximum y resolution to res.
-pa rat Set the pixel aspect ratio (height over width) to rat.
Either the x or the y resolution will be reduced so that the
pixels have this ratio for the specified view. If rat is
zero, then the x and y resolutions will adhere to the given
maxima.
-ps size Set the pixel sample spacing to the integer size. This
specifies the sample spacing (in pixels) for adaptive
subdivision on the image plane.
-pt frac Set the pixel sample tolerance to frac. If two samples
differ by more than this amount, a third sample is taken
between them.
-pj frac Set the pixel sample jitter to frac. Distributed ray-tracing
performs anti-aliasing by randomly sampling over pixels. A
value of one will randomly distribute samples over full
pixels. A value of zero samples pixel centers only. A value
between zero and one is usually best for low-resolution
images.
-pm frac Set the pixel motion blur to frac. In an animated sequence,
the exact view will be blurred between the previous view and
the next view as though a shutter were open this fraction of
a frame time. (See the -S option regarding animated
sequences.) The first view will be blurred according to the
difference between the initial view set on the command line
and the first view taken from the standard input. It is not
advisable to use this option in combination with the
pmblur(1) program, since one takes the place of the other.
However, it may improve results with pmblur to use a very
small fraction with the -pm option, to avoid the ghosting
effect of too few time samples.
-pd dia Set the pixel depth-of-field aperture to a diameter of dia
(in world coordinates). This will be used in conjunction
with the view focal distance, indicated by the length of the
view direction vector given in the -vd option. It is not
advisable to use this option in combination with the
pdfblur(1) program, since one takes the place of the other.
However, it may improve results with pdfblur to use a very
small fraction with the -pd option, to avoid the ghosting
effect of too few samples.
-dj frac Set the direct jittering to frac. A value of zero samples
each source at specific sample points (see the -ds option
below), giving a smoother but somewhat less accurate
rendering. A positive value causes rays to be distributed
over each source sample according to its size, resulting in
more accurate penumbras. This option should never be greater
than 1, and may even cause problems (such as speckle) when
the value is smaller. A warning about aiming failure will
issued if frac is too large. It is usually wise to turn off
image sampling when using direct jitter by setting -ps to 1.
-ds frac Set the direct sampling ratio to frac. A light source will
be subdivided until the width of each sample area divided by
the distance to the illuminated point is below this ratio.
This assures accuracy in regions close to large area sources
at a slight computational expense. A value of zero turns
source subdivision off, sending at most one shadow ray to
each light source.
-dt frac Set the direct threshold to frac. Shadow testing will stop
when the potential contribution of at least the next and at
most all remaining light source samples is less than this
fraction of the accumulated value. (See the -dc option
below.) The remaining light source contributions are
approximated statistically. A value of zero means that all
light source samples will be tested for shadow.
-dc frac Set the direct certainty to frac. A value of one guarantees
that the absolute accuracy of the direct calculation will be
equal to or better than that given in the -dt specification.
A value of zero only insures that all shadow lines resulting
in a contrast change greater than the -dt specification will
be calculated.
-dr N Set the number of relays for secondary sources to N. A value
of 0 means that secondary sources will be ignored. A value
of 1 means that sources will be made into first generation
secondary sources; a value of 2 means that first generation
secondary sources will also be made into second generation
secondary sources, and so on.
-dp D Set the secondary source presampling density to D. This is
the number of samples per steradian that will be used to
determine ahead of time whether or not it is worth following
shadow rays through all the reflections and/or transmissions
associated with a secondary source path. A value of 0 means
that the full secondary source path will always be tested for
shadows if it is tested at all.
-dv Boolean switch for light source visibility. With this switch
off, sources will be black when viewed directly although they
will still participate in the direct calculation. This
option may be desirable in conjunction with the -i option so
that light sources do not appear in the output.
-sj frac Set the specular sampling jitter to frac. This is the degree
to which the highlights are sampled for rough specular
materials. A value of one means that all highlights will be
fully sampled using distributed ray tracing. A value of zero
means that no jittering will take place, and all reflections
will appear sharp even when they should be diffuse. This may
be desirable when used in combination with image sampling
(see -ps option above) to obtain faster renderings.
-st frac Set the specular sampling threshold to frac. This is the
minimum fraction of reflection or transmission, under which
no specular sampling is performed. A value of zero means
that highlights will always be sampled by tracing reflected
or transmitted rays. A value of one means that specular
sampling is never used. Highlights from light sources will
always be correct, but reflections from other surfaces will
be approximated using an ambient value. A sampling threshold
between zero and one offers a compromise between image
accuracy and rendering time.
-bv Boolean switch for back face visibility. With this switch
off, back faces of opaque objects will be invisible to all
rays. This is dangerous unless the model was constructed
such that all surface normals on opaque objects face outward.
Although turning off back face visibility does not save much
computation time under most circumstances, it may be useful
as a tool for scene debugging, or for seeing through one-
sided walls from the outside. This option has no effect on
transparent or translucent materials.
-av red grn blu
Set the ambient value to a radiance of red grn blu . This is
the final value used in place of an indirect light
calculation. If the number of ambient bounces is one or
greater and the ambient value weight is non-zero (see -aw and
-ab below), this value may be modified by the computed
indirect values to improve overall accuracy.
-aw N Set the relative weight of the ambient value given with the
-av option to N. As new indirect irradiances are computed,
they will modify the default ambient value in a moving
average, with the specified weight assigned to the initial
value given on the command and all other weights set to 1.
If a value of 0 is given with this option, then the initial
ambient value is never modified. This is the safest value
for scenes with large differences in indirect contributions,
such as when both indoor and outdoor (daylight) areas are
visible.
-ab N Set the number of ambient bounces to N. This is the maximum
number of diffuse bounces computed by the indirect
calculation. A value of zero implies no indirect
calculation.
-ar res Set the ambient resolution to res. This number will
determine the maximum density of ambient values used in
interpolation. Error will start to increase on surfaces
spaced closer than the scene size divided by the ambient
resolution. The maximum ambient value density is the scene
size times the ambient accuracy (see the -aa option below)
divided by the ambient resolution. The scene size can be
determined using getinfo(1) with the -d option on the input
octree. A value of zero is interpreted as unlimited
resolution.
-aa acc Set the ambient accuracy to acc. This value will
approximately equal the error from indirect illuminance
interpolation. A value of zero implies no interpolation.
-ad N Set the number of ambient divisions to N. The error in the
Monte Carlo calculation of indirect illuminance will be
inversely proportional to the square root of this number. A
value of zero implies no indirect calculation.
-as N Set the number of ambient super-samples to N. Super-samples
are applied only to the ambient divisions which show a
significant change.
-af fname Set the ambient file to fname. This is where indirect
illuminance will be stored and retrieved. Normally, indirect
illuminance values are kept in memory and lost when the
program finishes or dies. By using a file, different
invocations can share illuminance values, saving time in the
computation. Also, by creating an ambient file during a low
resolution rendering, better results can be obtained in a
second high resolution pass. The ambient file is in a
machine-independent binary format which may be examined with
lookamb(1).
The ambient file may also be used as a means of communication
and data sharing between simultaneously executing processes.
The same file may be used by multiple processes, possibly
running on different machines and accessing the file via the
network (ie. nfs(4)). The network lock manager lockd(8) is
used to insure that this information is used consistently.
If any calculation parameters are changed or the scene is
modified, the old ambient file should be removed so that the
calculation can start over from scratch. For convenience,
the original ambient parameters are listed in the header of
the ambient file. Getinfo(1) may be used to print out this
information.
-ae mod Append mod to the ambient exclude list, so that it will not
be considered during the indirect calculation. This is a
hack for speeding the indirect computation by ignoring
certain objects. Any object having mod as its modifier will
get the default ambient level rather than a calculated value.
Any number of excluded modifiers may be given, but each must
appear in a separate option.
-ai mod Add mod to the ambient include list, so that it will be
considered during the indirect calculation. The program can
use either an include list or an exclude list, but not both.
-aE file Same as -ae, except read modifiers to be excluded from file.
The RAYPATH environment variable determines which directories
are searched for this file. The modifier names are separated
by white space in the file.
-aI file Same as -ai, except read modifiers to be included from file.
-me rext gext bext
Set the global medium extinction coefficient to the indicated
color, in units of 1/distance (distance in world
coordinates). Light will be scattered or absorbed over
distance according to this value. The ratio of scattering to
total scattering plus absorption is set by the albedo
parameter, described below.
-ma ralb galb balb
Set the global medium albedo to the given value between 0 0 0
and 1 1 1. A zero value means that all light not transmitted
by the medium is absorbed. A unitary value means that all
light not transmitted by the medium is scattered in some new
direction. The isotropy of scattering is determined by the
Heyney-Greenstein parameter, described below.
-mg gecc Set the medium Heyney-Greenstein eccentricity parameter to
gecc. This parameter determines how strongly scattering
favors the forward direction. A value of 0 indicates
perfectly isotropic scattering. As this parameter approaches
1, scattering tends to prefer the forward direction.
-ms sampdist
Set the medium sampling distance to sampdist, in world
coordinate units. During source scattering, this will be the
average distance between adjacent samples. A value of 0
means that only one sample will be taken per light source
within a given scattering volume.
-i Boolean switch to compute irradiance rather than radiance
values. This only affects the final result, substituting a
Lambertian surface and multiplying the radiance by pi. Glass
and other transparent surfaces are ignored during this stage.
Light sources still appear with their original radiance
values, though the -dv option (above) may be used to override
this.
-u Boolean switch to control uncorrelated random sampling. When
"off", a low-discrepancy sequence is used, which reduces
variance but can result in a brushed appearance in specular
highlights. When "on", pure Monte Carlo sampling is used in
all calculations.
-lr N Limit reflections to a maximum of N, if N is a positive
integer. If N is zero, then Russian roulette is used for ray
termination, and the -lw setting (below) must be positive.
If N is a negative integer, then this sets the upper limit of
reflections past which Russian roulette will be used. In
scenes with dielectrics and total internal reflection, a
setting of 0 (no limit) may cause a stack overflow.
-lw frac Limit the weight of each ray to a minimum of frac. During
ray-tracing, a record is kept of the estimated contribution
(weight) a ray would have in the image. If this weight is
less than the specified minimum and the -lr setting (above)
is positive, the ray is not traced. Otherwise, Russian
roulette is used to continue rays with a probability equal to
the ray weight divided by the given frac.
-S seqstart
Instead of generating a single picture based only on the view
parameters given on the command line, this option causes
rpict to read view options from the standard input and for
each line containing a valid view specification, generate a
corresponding picture. This option is most useful for
generating animated sequences, though it may also be used to
control rpict from a remote process for network-distributed
rendering. Seqstart is a positive integer that will be
associated with the first output frame, and incremented for
successive output frames. By default, each frame is
concatenated to the output stream, but it is possible to
change this action using the -o option (described below).
Multiple frames may be later extracted from the output using
ra_rgbe(1).
Note that the octree may not be read from the standard input
when using this option.
-o fspec Send the picture(s) to the file(s) given by fspec instead of
the standard output. If this option is used in combination
with -S and fspec contains an integer field for printf(3)
(eg. "%03d") then the actual output file name will include
the current frame number. Rpict will not allow a picture
file to be clobbered (overwritten) with this option. If an
image in a sequence already exists (-S option), rpict will
skip until it reaches an image that doesn’t, or the end of
the sequence. This is useful for running rpict on multiple
machines or processors to render the same sequence, as each
process will skip to the next frame that needs rendering.
-r fn Recover pixel information from the file fn. If the program
gets killed during picture generation, the information may be
recovered using this option. The view parameters and picture
dimensions are also recovered from fn if possible. The other
options should be identical to those which created fn, or an
inconsistent picture may result. If fn is identical to the
file specification given with the -o option, rpict will
rename the file prior to copying its contents. This insures
that the old file is not overwritten accidentally. (See also
the -ro option, below.)
If fn is an integer and the recover option is used in
combination with the -S option, then rpict skips a number of
view specifications on its input equal to the difference
between fn and seqstart. Rpict then performs a recovery
operation on the file constructed from the frame number fn
and the output file specification given with the -o option.
This provides a convenient mechanism for recovering in the
middle of an aborted picture sequence.
The recovered file will be removed if the operation is
successful. If the recover operation fails (due to lack of
disk space) and the output file and recover file
specifications are the same, then the original information
may be left in a renamed temporary file. (See FILES section,
below.)
-ro fspec This option causes pixel information to be recovered from and
subsequently returned to the picture file fspec. The effect
is the same as specifying identical recover and output file
names with the -r and -o options.
-z fspec Write pixel distances out to the file fspec. The values are
written as short floats, one per pixel in scanline order, as
required by pinterp(1). Similar to the -o option, the actual
file name will be constructed using printf and the frame
number from the -S option. If used with the -r option, -z
also recovers information from an aborted rendering.
-P pfile Execute in a persistent mode, using pfile as the control
file. This option must be used together with -S, and is
incompatible with the recover option (-r). Persistent
execution means that after reaching end-of-file on its input,
rpict will fork a child process that will wait for another
rpict command with the same -P option to attach to it. (Note
that since the rest of the command line options will be those
of the original invocation, it is not necessary to give any
arguments besides -P for subsequent calls.) Killing the
process is achieved with the kill(1) command. (The process
ID in the first line of pfile may be used to identify the
waiting rpict process.) This option may be less useful than
the -PP variation, explained below.
-PP pfile Execute in continuous-forking persistent mode, using pfile as
the control file. The difference between this option and the
-P option described above is the creation of multiple
duplicate processes to handle any number of attaches. This
provides a simple and reliable mechanism of memory sharing on
most multiprocessing platforms, since the fork(2) system call
will share memory on a copy-on-write basis. This option may
be used with rpiece(1) to efficiently render a single image
using multiple processors on the same host.
-t sec Set the time between progress reports to sec. A progress
report writes the number of rays traced, the percentage
completed, and the CPU usage to the standard error. Reports
are given either automatically after the specified interval,
or when the process receives a continue (-CONT) signal (see
kill(1)). A value of zero turns automatic reporting off.
-e efile Send error messages and progress reports to efile instead of
the standard error.
-w Boolean switch for warning messages. The default is to print
warnings, so the first appearance of this option turns them
off.
EXAMPLE
rpict -vp 10 5 3 -vd 1 -.5 0 scene.oct > scene.hdr
rpict -S 1 -o frame%02d.hdr scene.oct < keyframes.vf
ENVIRONMENT
RAYPATH the directories to check for auxiliary files.
FILES
/tmp/rtXXXXXX common header information for picture sequence
rfXXXXXX temporary name for recover file
DIAGNOSTICS
If the program terminates from an input related error, the exit status
will be 1. A system related error results in an exit status of 2. If
the program receives a signal that is caught, it will exit with a
status of 3. In each case, an error message will be printed to the
standard error, or to the file designated by the -e option.
AUTHOR
Greg Ward
SEE ALSO
getinfo(1), lookamb(1), oconv(1), pdfblur(1), pfilt(1), pinterp(1),
pmblur(1), printf(3), ra_rgbe(1), rad(1), rtrace(1), rvu(1)