.\" RCSid "$Id: pabopto2xyz.1,v 1.3 2025/04/11 20:54:38 greg Exp $"
.TH PABOPTO2XYZ 1 3/1/2021 RADIANCE
.SH NAME
pabopto2xyz - convert a collection of single-channel BSDF measurements to CIE-XYZ colorimetry
.SH SYNOPSIS
.B pabopto2xyz
[
.B "\-m X1 X2 X3 Y1 Y2 Y3 Z1 Z2 Z3"
][
.B "\-o basename"
][
.B "\-n nprocs"
]
.B "s1files.txt s2files.txt s3files.txt"
.SH DESCRIPTION
.I Pabopto2xyz
takes three sets of standard single-channel BSDF files, each
measured with a different light source and/or sensor filter to select
different wavelengths, combining them into an equivalent set of 3-channel BSDF data
files with CIE-XYZ colorimetry.
The 3x3 transform from the input file measurements to CIE XYZ color space is
set by the
.I \-m
option.
The default coefficients correspond to a specific set of filters in use at LBNL,
and are probably not applicable to any other instrument.
.PP
The
.I \-o
option is used to set the base output file name, which defaults to "pabopto_xyz".
To this base name, the theta and phi angles are added, along with a ".txt" suffix.
.PP
The
.I \-n
option may be supplied on Unix systems for multiple processes to speed up
the conversion.
.PP
The BSDF measurement file names must be listed in
the three required input files,
dileneated in each by white space.
File names or paths therein may not contain white space, and quoting/escaping
is not supported.
The same incident directions must be provided in all three measurement sets,
but may be broken into different files.
(I.e., two or more BSDF files may correspond to the same incident direction.)\0
Only one file will be produced for each incident direction in the output.
.PP
.I Pabopto2xyz
works by resampling the second and third input channels to correspond to the
exiting directions measured in the first channel.
A 2-D interpolant is applied at each incident direction for channels 2 and 3,
the given 3x3 matrix is applied,
and a combined virtual measurement is produced in output files beginning with
the given base name.
For this reason, it is often preferably to place the "green" or "near-Y"
channel first.
.PP
The combined data files produced by
.I pabopto2xyz
are subsequently passed to
.I pabopto2bsdf(1)
to produce a Scattering Interpolant Representation (SIR) file for further
processing.
.SH EXAMPLE
To combine three sets of measurements in a REC709 color space and produce
a CIE-XYZ file for pabopto2bsdf, which produces a color SIR file:
.IP "" .2i
pabopto2xyz -m .358 .412 .180 .715 .213 .072 .119 .019 .951 -o blinds_xyz filesG.txt filesR.txt filesB.txt
.br
pabopto2bsdf blinds_xyz*.txt > blinds_xyz.sir
.SH AUTHOR
Greg Ward
.SH "SEE ALSO"
bsdf2klems(1), bsdf2rad(1), bsdf2ttree(1), bsdfview(1), genBSDF(1),
pabopto2bsdf(1)