man/man1/genBSDF.1

.\" RCSid $Id: genBSDF.1,v 1.2 2010/09/04 15:19:28 greg Exp $
.TH GENBSDF 1 9/3/2010 RADIANCE
.SH NAME
genBSDF - generate BSDF description from Radiance or MGF input
.SH SYNOPSIS
.B genBSDF
[
.B "\-c Nsamp"
][
.B "\-n Nproc"
][
.B "{+|-}forward"
][
.B "{+|-}backward"
][
.B "{+|-}mgf"
][
.B "{+|-}geom
][
.B "\-dim Xmin Xmax Ymin Ymax Zmin Zmax"
]
[
.B "geom .."
]
.SH DESCRIPTION
.I GenBSDF
computes a bidirectional scattering distribution function from
a Radiance or MGF scene description given on the input.
The program assumes the input is in Radiance format unless the
.I \+mgf
option is specified.
The output conforms to the LBNL Window 6 XML standard for BSDF data,
and will include an MGF representation of the input geometry if the
.I \+geom
option is given.
(This is the default, and may be switched off using
.I \-geom.)\0
.PP
Normally,
.I genBSDF
computes components needed by a backwards ray-tracing process,
.I \+backward.
If both forward and backward (front and back) distributions are needed, the
.I \+forward
option may be given.
To turn off backward components, use the
.I \-backward
option.
Computing both components takes about twice as long as one component.
.PP
The geometry must fit a rectangular profile, whose width is along the X-axis,
height is in the Y-axis, and depth is in the Z-axis.
The positive Z-axis points into the room, and the input geometry should
not extend into the room.
(I.e., it should not contain any positive Z values, since the putative 
emitting surface is assumed to lie at Z=0.)\0
The entire window system should be modeled, including sills and
edge geometry anticipated in the final installation, otherwise
accuracy will be impaired.
Similarly, materials in the description should be carefully measured.
.PP
Normally, the input geometry will be positioned according to its actual
bounding box, but this may be overridden with the
.I \-dim
option.
Use this in cases where the fenestration system is designed to fit a
smaller (or larger) opening or is offset somehow.
.PP
The variance in the results may be reduced by increasing the number of
samples per incident direction using the
.I \-c
option.
This value defaults to 1000 samples distributed over the incoming plane
for each of the 145 Klems hemisphere directions.
.PP
In some cases, the processing time may be reduced by the
.I \-n
option, which specifies the number of simultaneous
.I rtrace(1)
processes to run in
.I rtcontrib(1).
.SH EXAMPLE
To create a BSDF description including geometry from a set of venetian blinds:
.IP "" .2i
genblinds blind_white blind1 .07 3 1.5 30 40 | xform -rz -90 -rx 90 > blind1.rad
.br
genBSDF blind_white.mat glazing.rad blind1.rad > blind1.xml
.SH NOTES
Currently,
.I genBSDF
computes only the forward visible transmitted component,
though the XML specification provides for front and back
transmission and reflection as well.
.SH AUTHOR
Greg Ward
.SH "SEE ALSO"
dctimestep(1), genklemsamp(1), genskyvec(1), mkillum(1), rtcontrib(1), rtrace(1)
Revision:	1.3
Committed:	Mon Feb 21 22:48:50 2011 UTC (14 years, 8 months ago) by greg
Branch:	MAIN
Changes since 1.2:	+19 -3 lines
Log Message:	Added BRDF computation to genBSDF
#	User	Rev	Content
1	greg	1.3	.\" RCSid $Id: genBSDF.1,v 1.2 2010/09/04 15:19:28 greg Exp $
2	greg	1.1	.TH GENBSDF 1 9/3/2010 RADIANCE
3			.SH NAME
4			genBSDF - generate BSDF description from Radiance or MGF input
5			.SH SYNOPSIS
6			.B genBSDF
7			[
8			.B "\-c Nsamp"
9			][
10			.B "\-n Nproc"
11			][
12	greg	1.3	.B "{+\|-}forward"
13			][
14			.B "{+\|-}backward"
15			][
16	greg	1.1	.B "{+\|-}mgf"
17			][
18			.B "{+\|-}geom
19			][
20			.B "\-dim Xmin Xmax Ymin Ymax Zmin Zmax"
21			]
22			[
23			.B "geom .."
24			]
25			.SH DESCRIPTION
26			.I GenBSDF
27	greg	1.3	computes a bidirectional scattering distribution function from
28	greg	1.1	a Radiance or MGF scene description given on the input.
29			The program assumes the input is in Radiance format unless the
30			.I \+mgf
31			option is specified.
32			The output conforms to the LBNL Window 6 XML standard for BSDF data,
33			and will include an MGF representation of the input geometry if the
34			.I \+geom
35			option is given.
36	greg	1.3	(This is the default, and may be switched off using
37	greg	1.1	.I \-geom.)\0
38			.PP
39	greg	1.3	Normally,
40			.I genBSDF
41			computes components needed by a backwards ray-tracing process,
42			.I \+backward.
43			If both forward and backward (front and back) distributions are needed, the
44			.I \+forward
45			option may be given.
46			To turn off backward components, use the
47			.I \-backward
48			option.
49			Computing both components takes about twice as long as one component.
50			.PP
51	greg	1.1	The geometry must fit a rectangular profile, whose width is along the X-axis,
52			height is in the Y-axis, and depth is in the Z-axis.
53			The positive Z-axis points into the room, and the input geometry should
54			not extend into the room.
55			(I.e., it should not contain any positive Z values, since the putative
56			emitting surface is assumed to lie at Z=0.)\0
57			The entire window system should be modeled, including sills and
58			edge geometry anticipated in the final installation, otherwise
59			accuracy will be impaired.
60			Similarly, materials in the description should be carefully measured.
61			.PP
62			Normally, the input geometry will be positioned according to its actual
63			bounding box, but this may be overridden with the
64			.I \-dim
65			option.
66			Use this in cases where the fenestration system is designed to fit a
67			smaller (or larger) opening or is offset somehow.
68			.PP
69			The variance in the results may be reduced by increasing the number of
70			samples per incident direction using the
71			.I \-c
72			option.
73			This value defaults to 1000 samples distributed over the incoming plane
74			for each of the 145 Klems hemisphere directions.
75			.PP
76			In some cases, the processing time may be reduced by the
77			.I \-n
78			option, which specifies the number of simultaneous
79			.I rtrace(1)
80			processes to run in
81			.I rtcontrib(1).
82			.SH EXAMPLE
83			To create a BSDF description including geometry from a set of venetian blinds:
84			.IP "" .2i
85	greg	1.2	genblinds blind_white blind1 .07 3 1.5 30 40 \| xform -rz -90 -rx 90 > blind1.rad
86	greg	1.1	.br
87	greg	1.2	genBSDF blind_white.mat glazing.rad blind1.rad > blind1.xml
88	greg	1.1	.SH NOTES
89			Currently,
90			.I genBSDF
91			computes only the forward visible transmitted component,
92			though the XML specification provides for front and back
93			transmission and reflection as well.
94			.SH AUTHOR
95			Greg Ward
96			.SH "SEE ALSO"
97			dctimestep(1), genklemsamp(1), genskyvec(1), mkillum(1), rtcontrib(1), rtrace(1)