.\" RCSid "$Id: bsdf2rad.1,v 1.1 2017/08/11 21:39:52 greg Exp $"
.TH BSDF2RAD 1 8/11/2017 RADIANCE
.SH NAME
bsdf2rad - create a RADIANCE visualization of a BSDF representation
.SH SYNOPSIS
.B bsdf2rad
bsdf.xml
.br
or
.br
.B bsdf2rad
hemi1.sir
[
hemi2.sir ..
]
.br
.SH DESCRIPTION
.I Bsdf2rad
takes a bidirectional scattering distribution function (BSDF)
and plots it as a RADIANCE scene file.
In the first form,
.I bsdf2rad
takes a single XML file representing a Klems or tensor tree, plotting
as many scattering hemispheres as are present in the file.
In the second form,
.I bsdf2rad
takes up to four scattering interpolation representation (SIR) files,
each depicting the BSDF from one side of one incident hemisphere,
and plots them together.
An XML BSDF description may be imported from outside RADIANCE, or
produced by
.I genBSDF(1),
.I bsdf2klems(1),
or
.I bsdf2ttree(1).
(A program that produces SIR files is
.I pabopto2bsdf(1).)\0
.PP
The output of
.I bsdf2rad
is a RADIANCE scene that contains a selection of 3-D plots showing
the given material's reflection and transmission scattering.
This description is normally sent to
.I oconv(1)
to create an octree for rendering using
.I rad(1),
.I rvu(1),
or
.I rpict(1).
.PP
To the right (+X) of the scene, the front incident hemisphere will be plotted.
To the left (-X) of the scene, the back incident hemisphere will be plotted.
Depending on the input, only one or the other hemisphere may be present.
In the case of an XML input, the hemispheres will be made of the specified
BSDF material, and the scene
will include a single (distant) light source shining straight
down from overhead (+Z direction).
.PP
Pink arrows will indicate the "through" (view) and "mirror"
(specular reflection) directions for each scatter plot.
The logarithmic scale of the BSDF plots themselves will be determined
automatically by the data and shown in a legend that lies between the
two hemisphere, or to the side if there is only one.
The incident direction may be read from the position of
each plot, where hemisphere grid lines are separated by
15 degree increments in the polar (theta, latitude) angle, and by
30 degree increments in the azimuthal (phi, longitude) angle.
The center (+Z) of each hemisphere corresponds to normal incidence,
and the right (+X) direction corresponds to a zero phi angle.
Positive phi is read counter-clockwise from above,
and a phi of 90 degrees (+Y) typically corresponds
to a material's "up" orientation.
.SH EXAMPLE
To view a BSDF XML representation:
.IP "" .2i
bsdf2rad cloth.xml | oconv - > cloth.oct
.br
rvu -vp 0 -50 50 -vd 0 50 -50 -vh 45 -vv 30 cloth.oct
.PP
To render an SIR description of a BRDF:
.IP "" .2i
bsdf2rad front_refl.sir back_refl.sir > refl.rad
oconv -f refl.rad | rpict -vf good.vf > refl_good.hdr
.SH AUTHOR
Greg Ward
.SH "SEE ALSO"
bsdf2klems(1), bsdf2ttree(1), genBSDF(1),
bsdfview(1), oconv(1), pabopto2bsdf(1), rad(1), rpict(1), rvu(1)