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.\" RCSid $Id: genskyvec.1,v 1.7 2023/12/06 01:27:00 greg Exp $
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.TH GENSKYVEC 1 12/09/09 RADIANCE
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.SH NAME
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genskyvec - compute patch radiance averages for a specific sky
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.SH SYNOPSIS
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.B genskyvec
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[
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.B "\-h"
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][
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.B "\-m N"
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][
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.B "\-c r g b"
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][
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.B "\-d"
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]
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.SH DESCRIPTION
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.I Genskyvec
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samples the
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.I Radinace
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sky description given on the standard input to generate a list of
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average patch radiances.
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If there is a sun in the description,
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.I genskyvec
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will include its contribution in the three nearest sky patches,
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distributing energy according to centroid proximity.
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.PP
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By default,
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.I genskyvec
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divides the sky into 2305 patches, plus one patch for the ground.
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This corresponds to Reinhart's extension of the Tregenza sky,
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where the original 145 patches are subdivided into 16 subpatches,
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except at the zenith.
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A different subdivision may be specified via the
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.I \-m
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option.
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The value given will be used to subdivide each dimension, so the
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default of 4 yields almost 16 times as many patches
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as the original Tregenza sky, which can be specified with
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.I "\-m 1."
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A higher resolution sky is generally better for daylight
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coefficient analysis where solar position is important.
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.PP
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The
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.I \-c
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option may be used to specify a color for the sky.
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The gray value should equal 1 for proper energy balance
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The default sky color is
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.I "\-c 0.960 1.004 1.118".
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.PP
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The
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.I \-d
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option may be used to produce a sun-only vector, with no sky contributions.
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If a time of day is selected or sky type that has no sun, then a zero vector
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is produced.
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.PP
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Normally, a header will be produced containing the number of rows and other
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information required by
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.I dctimestep(1).
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The
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.I \-h
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option may be used to elide this information header, producing data values only.
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.SH EXAMPLE
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To generate 578 patches corresponding to a 2x2 subdivision of the
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Tregenza sky on a sunny equinox noon:
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.IP "" .2i
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gensky 9 21 12 | genskyvec -m 2 > sky09_21_12.dat
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.SH AUTHOR
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Greg Ward
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.SH "SEE ALSO"
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dctimestep(1), genBSDF(1), gendaylit(1),
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gendaymtx(1), gensky(1), rcollate(1), rcomb(1),
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rcontrib(1), rmtxop(1), rtrace(1)
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