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.\" RCSid "$Id: bsdf2rad.1,v 1.4 2021/02/25 04:48:19 greg Exp $"
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.TH BSDF2RAD 1 8/11/2017 RADIANCE
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.SH NAME
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bsdf2rad - create a RADIANCE visualization of a BSDF representation
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.SH SYNOPSIS
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.B bsdf2rad
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[
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.B "\-r min max"
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]
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bsdf.xml
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.br
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or
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.br
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.B bsdf2rad
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[
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.B "\-r min max"
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]
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hemi1.sir
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[
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hemi2.sir ..
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]
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.br
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.SH DESCRIPTION
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.I Bsdf2rad
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takes a bidirectional scattering distribution function (BSDF)
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and plots it as a RADIANCE scene file.
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In the first form,
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.I bsdf2rad
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takes a single XML file representing a Klems or tensor tree BSDF, plotting
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as many scattering hemispheres as are present in the file.
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In the second form,
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.I bsdf2rad
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takes up to four scattering interpolation representation (SIR) files,
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each depicting the BSDF from one side of one incident hemisphere,
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and plots them together.
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An XML BSDF description may be imported from outside RADIANCE, or
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produced by
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.I genBSDF(1),
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.I bsdf2klems(1),
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or
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.I bsdf2ttree(1).
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(A program that produces SIR files is
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.I pabopto2bsdf(1).)\0
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.PP
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The output of
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.I bsdf2rad
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is a RADIANCE scene that contains a selection of 3-D plots showing
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the given material's reflection and transmission scattering.
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This description is normally sent to
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.I oconv(1)
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to create an octree for rendering using
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.I rad(1),
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.I rvu(1),
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or
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.I rpict(1).
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.PP
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To the right (+X) of the scene, the front incident hemisphere will be plotted.
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To the left (-X) of the scene, the back incident hemisphere will be plotted.
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Depending on the input, only one or the other hemisphere may be present.
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In the case of an XML input, the hemispheres will be made of the specified
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BSDF material, and the scene
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will include a single (distant) light source shining straight
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down from overhead (+Z direction).
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.PP
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Pink arrows will indicate the "through" (view) and "mirror"
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(specular reflection) directions for each scatter plot.
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The logarithmic scale of the BSDF plots themselves will be determined
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automatically by the data and shown in a legend that lies between the
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two hemisphere, or to the side if there is only one.
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The incident direction may be read from the position of
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each plot, where hemisphere grid lines are separated by
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15 degree increments in the polar (theta, latitude) angle, and by
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30 degree increments in the azimuthal (phi, longitude) angle.
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The center (+Z) of each hemisphere corresponds to normal incidence,
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and the right (+X) direction corresponds to a zero phi angle.
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Positive phi is read counter-clockwise from above,
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and a phi of 90 degrees (+Y) typically corresponds
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to a material's "up" orientation.
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.PP
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If an optional plotting range is given with the
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.I \-r
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option, this will override automatic settings from the BSDF input.
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This may be useful for comparing different BSDF sources.
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.SH EXAMPLE
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To view a BSDF XML representation:
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.IP "" .2i
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bsdf2rad cloth.xml | oconv - > cloth.oct
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.br
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rvu -vp 0 -50 50 -vd 0 50 -50 -vh 45 -vv 30 cloth.oct
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.PP
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To render an SIR description of a BRDF:
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.IP "" .2i
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bsdf2rad front_refl.sir back_refl.sir > refl.rad
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.br
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oconv -f refl.rad | rpict -vf good.vf > refl_good.hdr
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.SH AUTHOR
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Greg Ward
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.SH "SEE ALSO"
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bsdf2klems(1), bsdf2ttree(1), genBSDF(1),
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bsdfview(1), oconv(1), pabopto2bsdf(1), pabopto2xyz(1), rad(1), rpict(1), rvu(1)
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