RTRACE

xorg yorg zorg xdir ydir zdir

-fio

Format input according to the character i and output according to the character o. Rtrace understands the following input and output formats: ’a’ for ascii, ’f’ for single-precision floating point, and ’d’ for double-precision floating point. In addition to these three choices, the character ’c’ may be used to denote 4-byte RGBE (Radiance) color format for the output of individual color values only, and the -x and -y options should also be specified to create a valid output picture. If the output character is missing, the input format is used.

-ospec

Produce output fields according to spec. Characters are interpreted as follows:

o

origin (input)

d

direction (normalized)

v

value (radiance)

V

contribution (radiance)

w

weight

W

color coefficient

l

effective length of ray

L

first intersection distance

c

local (u,v) coordinates

p

point of intersection

n

normal at intersection (perturbed)

N

normal at intersection (unperturbed)

s

surface name

m

modifier name

M

material name

r

mirrored value contribution

x

unmirrored value contribution

R

mirrored ray length

X

unmirrored ray length

~

tilde (end of trace marker)

-te mod

Append mod to the trace exclude list, so that it will not be reported by the trace option (-o*t*). Any ray striking an object having mod as its modifier will not be reported to the standard output with the rest of the rays being traced. This option has no effect unless either the ’t’ or ’T’ option has been given as part of the output specifier. Any number of excluded modifiers may be given, but each must appear in a separate option.

-ti mod

Add mod to the trace include list, so that it will be reported by the trace option. The program can use either an include list or an exclude list, but not both.

-tE file

Same as -te, 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.

-tI file

Same as -ti, except read modifiers to be included from file.

-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 (below) may be used to override this. This option is especially useful in conjunction with ximage(1) for computing illuminance at scene points.

-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.

-I

Boolean switch to compute irradiance rather than radiance, with the input origin and direction interpreted instead as measurement point and orientation.

-h

Boolean switch for information header on output.

-x res

Set the x resolution to res. The output will be flushed after every res input rays if -y is set to zero. A value of one means that every ray will be flushed, whatever the setting of -y. A value of zero means that no output flushing will take place.

-y res

Set the y resolution to res. The program will exit after res scanlines have been processed, where a scanline is the number of rays given by the -x option, or 1 if -x is zero. A value of zero means the program will not halt until the end of file is reached.

-n nproc

Execute in parallel on nproc local processes. This option is incompatible with the -P and -PP, options. Multiple processes also do not work properly with ray tree output using any of the -o*t* options. There is no benefit from specifying more processes than there are cores available on the system or the -x setting, which forces a wait at each flush.

-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.

-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 sources 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 sources 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 is mostly for the program mkillum(1) to avoid inappropriate counting of light sources, but it may also be desirable in conjunction with the -i option.

-ss samp

Set the specular sampling to samp. For values less than 1, this is the degree to which the highlights are sampled for rough specular materials. A value greater than one causes multiple ray samples to be sent to reduce noise at a commmesurate cost. A value of zero means that no jittering will take place, and all reflections will appear sharp even when they should be diffuse.

-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 all objects will be invisible to view rays. This is dangerous unless the model was constructed such that all surface normals 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.

-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.

-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. The ambient file is in a machine-independent binary format which can be examined with lookamb(1).

-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.

-am frac

Maximum search radius for photon map lookups. Without this option, an initial maximum search radius is estimated for each photon map from the average photon distance to the distribution’s centre of gravity. It is then adapted to the photon density in subsequent lookups. This option imposes a global fixed maximum search radius for all photon maps, thus defeating the automatic adaptation. It is useful when multiple warnings about short photon lookups are issued. Note that this option does not conflict with the bandwidth specified with the -ap option; the number of photons found will not exceed the latter, but may be lower if the maximum search radius contains fewer photons, thus resulting in short lookups. Setting this radius too large, on the other hand, may degrade performance.

-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.

-lr N

Limit reflections to a maximum of N, if N is a positive integer. If N is zero or negative, then Russian roulette is used for ray termination, and the -lw setting (below) must be positive. If N is a negative integer, then this limits the maximum number of reflections even with Russian roulette. 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.

-ld

Boolean switch to limit ray distance. If this option is set, then rays will only be traced as far as the magnitude of each direction vector. Otherwise, vector magnitude is ignored and rays are traced to infinity.

-e efile

Send error messages and progress reports to efile instead of the standard error.

-w

Boolean switch to suppress warning messages.

-P pfile

Execute in a persistent mode, using pfile as the control file. Persistent execution means that after reaching end-of-file on its input, rtrace will fork a child process that will wait for another rtrace 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 rtrace process.) This option may be used with the -fr option of pinterp(1) to avoid the cost of starting up rtrace many times.

-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.

rtrace -ov scene.oct < samples.inp > radiance.out

ximage scene.hdr | rtrace -h -x 1 -i scene.oct | rcalc -e ’$1=47.4*$1+120*$2+11.6*$3’

vwrays -fd scene.hdr | rtrace -fda ‘vwrays -d scene.hdr‘ -os scene.oct

cnt 480 640 | rcalc -e ’xr:640;yr:480’ -f unusual_view.cal | rtrace -x 640 -y 480 -fac scene.oct > unusual.hdr

rtrace -h -ov -ab 1 -ap global.pm 50 -ap caustic.pm 50 scene.oct < samples.inp > illum.out

RAYPATH

the directories to check for auxiliary files.

/tmp/rtXXXXXX

common header information for picture sequence