man/man1/genBSDF.1

.\" RCSid $Id: genBSDF.1,v 1.18 2015/04/05 01:32:01 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 "\-r 'rcontrib opts...'"
][
.B "\-W"
][
.B "\-s 'x=string;y=string'"
][
.B "\-t{3|4} Nlog2"
][
.B "{+|-}C"
][
.B "{+|-}forward"
][
.B "{+|-}backward"
][
.B "{+|-}mgf"
][
.B "{+|-}geom unit"
][
.B "\-dim Xmin Xmax Ymin Ymax Zmin Zmax"
]
[
.B "geom .."
]
.br
or
.br
.B genBSDF
.B "\-recover tempdir"
.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, followed by one of "meter," "foot," "inch,"
"centimeter," or "millimeter," depending on the scene units.
The default is to include the provided geometry,
which is assumed to be in meters.
Geometry output can be supressed with the
.I \-geom
option, which must also be followed by one of the above length units.
.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, but
is recommended when rays will be impinging from either side.
.PP
The
.I \+C
option specifies that the output XML should include color information,
which is interpreted by the rendering programs.
The default option
.I \-C
reduces all BSDF data to grayscale.
.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 2000 samples distributed over the incoming plane
for each of the 145 Klems hemisphere directions.
.PP
On multi-core machines, processing time may be reduced by the
.I \-n
option, which specifies the number of simultaneous
processes to run in
.I rcontrib(1).
The
.I \-r
option may be used to specify a set of quoted arguments to be
included on the
.I rcontrib
command line.
.PP
The
.I \-W
option is passed to
.I wrapBSDF(1)
to prepare the XML file for WINDOW6.
Any
.I \-s
parameters are passed to the
.I \-f
option of
.I wrapBSDF,
controlling XML fields such as
the Manufacturer (e.g., -s m=MF) and device Name (e.g, -s n=NM).
.PP
The
.I \-t4
mode computes a non-uniform BSDF represented as a rank 4 tensor tree,
suitable for use in the Radiance rendering tools.
The parameter given to this option is the log to the base 2 of the
sampling resolution in each dimension, and must be an integer.
The
.I \-c
setting should be adjusted so that an appropriate number of samples
lands in each region.
A
.I \-t4
parameter of 5 corresponds to 32x32 or 1024 output regions, so a
.I \-c
setting of 10240 would provide 10 samples per region on average.
Increasing the resolution to 6 corresponds to 64x64 or 4096
regions, so the
.I \-c
setting would need to be increased by a factor of 4 to provide
the same accuracy in each region.
.PP
The
.I \-t3
mode is similar to
.I \-t4
but computes a rank 3 tensor tree rather than rank 4.
This provides a much faster computation, but only works
in special circumstances.
Specifically, do NOT use this option if the system is not in fact isotropic.
I.e., only use
.I \-t3
when you are certain that the system has a high degree of radial symmetry.
Again, the parameter to this option sets the maximum resolution as
a power of 2 in each dimension, but in this case there is one less
dimension being sampled.
.PP
The
.I \-recover
option is available for continuing calculations that were killed by
the system or the user.
Unfortunately, genBSDF puts its temporary files in a directory
that is often cleaned up after reboot, so this may not always work.
.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 -r @rtc.opt blind_white.mat glazing.rad blind1.rad > blind1.xml
.PP
To create a non-uniform, anisotropic BSDF distribution with a maximum
resolution of 128x128 from the same description:
.IP "" .2i
genBSDF -r @rtc.opt -t4 7 -c 160000 blind_white.mat glazing.rad blind1.rad > blind12.xml
.SH NOTES
The variable resolution (tensor tree) BSDF representation is not supported
by all software and applicatons, and should be used with caution.
It provides practical, high-resolution data for use in the
Radiance rendering programs, but does not work in the matrix formulation
of the daylight coefficient method for example.
Also, third party tools generally expect or require a fixed number of sample
directions using the Klems directions or similar.
.SH AUTHOR
Greg Ward
.SH "SEE ALSO"
dctimestep(1), gendaymtx(1), genklemsamp(1), genskyvec(1), mkillum(1),
pkgBSDF(1), rcontrib(1), rfluxmtx(1), rmtxop(1), rtrace(1) wrapBSDF(1)
Revision:	1.19
Committed:	Fri Sep 16 17:54:56 2016 UTC (9 years, 1 month ago) by greg
Branch:	MAIN
Changes since 1.18:	+13 -1 lines
Log Message:	Added -recover option to genBSDF at Lars Grobe's request
#	User	Rev	Content
1	greg	1.19	.\" RCSid $Id: genBSDF.1,v 1.18 2015/04/05 01:32:01 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	1.10	.B "\-r 'rcontrib opts...'"
13	greg	1.4	][
14	greg	1.14	.B "\-W"
15			][
16	greg	1.15	.B "\-s 'x=string;y=string'"
17	greg	1.14	][
18	greg	1.6	.B "\-t{3\|4} Nlog2"
19			][
20	greg	1.17	.B "{+\|-}C"
21			][
22	greg	1.3	.B "{+\|-}forward"
23			][
24			.B "{+\|-}backward"
25			][
26	greg	1.1	.B "{+\|-}mgf"
27			][
28	greg	1.7	.B "{+\|-}geom unit"
29	greg	1.1	][
30			.B "\-dim Xmin Xmax Ymin Ymax Zmin Zmax"
31			]
32			[
33			.B "geom .."
34			]
35	greg	1.19	.br
36			or
37			.br
38			.B genBSDF
39			.B "\-recover tempdir"
40	greg	1.1	.SH DESCRIPTION
41			.I GenBSDF
42	greg	1.3	computes a bidirectional scattering distribution function from
43	greg	1.1	a Radiance or MGF scene description given on the input.
44			The program assumes the input is in Radiance format unless the
45			.I \+mgf
46			option is specified.
47			The output conforms to the LBNL Window 6 XML standard for BSDF data,
48			and will include an MGF representation of the input geometry if the
49			.I \+geom
50	greg	1.7	option is given, followed by one of "meter," "foot," "inch,"
51			"centimeter," or "millimeter," depending on the scene units.
52			The default is to include the provided geometry,
53			which is assumed to be in meters.
54			Geometry output can be supressed with the
55			.I \-geom
56			option, which must also be followed by one of the above length units.
57	greg	1.1	.PP
58	greg	1.3	Normally,
59			.I genBSDF
60			computes components needed by a backwards ray-tracing process,
61			.I \+backward.
62			If both forward and backward (front and back) distributions are needed, the
63			.I \+forward
64			option may be given.
65			To turn off backward components, use the
66			.I \-backward
67			option.
68	greg	1.12	Computing both components takes about twice as long as one component, but
69			is recommended when rays will be impinging from either side.
70	greg	1.3	.PP
71	greg	1.17	The
72			.I \+C
73			option specifies that the output XML should include color information,
74			which is interpreted by the rendering programs.
75	greg	1.18	The default option
76			.I \-C
77	greg	1.17	reduces all BSDF data to grayscale.
78			.PP
79	greg	1.1	The geometry must fit a rectangular profile, whose width is along the X-axis,
80			height is in the Y-axis, and depth is in the Z-axis.
81			The positive Z-axis points into the room, and the input geometry should
82			not extend into the room.
83			(I.e., it should not contain any positive Z values, since the putative
84			emitting surface is assumed to lie at Z=0.)\0
85			The entire window system should be modeled, including sills and
86			edge geometry anticipated in the final installation, otherwise
87			accuracy will be impaired.
88			Similarly, materials in the description should be carefully measured.
89			.PP
90			Normally, the input geometry will be positioned according to its actual
91			bounding box, but this may be overridden with the
92			.I \-dim
93			option.
94			Use this in cases where the fenestration system is designed to fit a
95			smaller (or larger) opening or is offset somehow.
96			.PP
97			The variance in the results may be reduced by increasing the number of
98			samples per incident direction using the
99			.I \-c
100			option.
101	greg	1.9	This value defaults to 2000 samples distributed over the incoming plane
102	greg	1.1	for each of the 145 Klems hemisphere directions.
103			.PP
104	greg	1.11	On multi-core machines, processing time may be reduced by the
105	greg	1.1	.I \-n
106			option, which specifies the number of simultaneous
107			processes to run in
108	greg	1.10	.I rcontrib(1).
109	greg	1.4	The
110			.I \-r
111			option may be used to specify a set of quoted arguments to be
112			included on the
113	greg	1.10	.I rcontrib
114	greg	1.4	command line.
115	greg	1.6	.PP
116			The
117	greg	1.14	.I \-W
118	greg	1.15	option is passed to
119			.I wrapBSDF(1)
120			to prepare the XML file for WINDOW6.
121			Any
122			.I \-s
123			parameters are passed to the
124	greg	1.14	.I \-f
125	greg	1.15	option of
126			.I wrapBSDF,
127			controlling XML fields such as
128			the Manufacturer (e.g., -s m=MF) and device Name (e.g, -s n=NM).
129	greg	1.14	.PP
130			The
131	greg	1.6	.I \-t4
132			mode computes a non-uniform BSDF represented as a rank 4 tensor tree,
133			suitable for use in the Radiance rendering tools.
134			The parameter given to this option is the log to the base 2 of the
135			sampling resolution in each dimension, and must be an integer.
136			The
137			.I \-c
138			setting should be adjusted so that an appropriate number of samples
139			lands in each region.
140			A
141			.I \-t4
142			parameter of 5 corresponds to 32x32 or 1024 output regions, so a
143			.I \-c
144	greg	1.9	setting of 10240 would provide 10 samples per region on average.
145	greg	1.6	Increasing the resolution to 6 corresponds to 64x64 or 4096
146			regions, so the
147			.I \-c
148			setting would need to be increased by a factor of 4 to provide
149			the same accuracy in each region.
150			.PP
151			The
152			.I \-t3
153			mode is similar to
154			.I \-t4
155			but computes a rank 3 tensor tree rather than rank 4.
156			This provides a much faster computation, but only works
157			in special circumstances.
158			Specifically, do NOT use this option if the system is not in fact isotropic.
159			I.e., only use
160			.I \-t3
161			when you are certain that the system has a high degree of radial symmetry.
162			Again, the parameter to this option sets the maximum resolution as
163			a power of 2 in each dimension, but in this case there is one less
164			dimension being sampled.
165	greg	1.19	.PP
166			The
167			.I \-recover
168			option is available for continuing calculations that were killed by
169			the system or the user.
170			Unfortunately, genBSDF puts its temporary files in a directory
171			that is often cleaned up after reboot, so this may not always work.
172	greg	1.1	.SH EXAMPLE
173			To create a BSDF description including geometry from a set of venetian blinds:
174			.IP "" .2i
175	greg	1.2	genblinds blind_white blind1 .07 3 1.5 30 40 \| xform -rz -90 -rx 90 > blind1.rad
176	greg	1.1	.br
177	greg	1.4	genBSDF -r @rtc.opt blind_white.mat glazing.rad blind1.rad > blind1.xml
178	greg	1.6	.PP
179			To create a non-uniform, anisotropic BSDF distribution with a maximum
180			resolution of 128x128 from the same description:
181			.IP "" .2i
182			genBSDF -r @rtc.opt -t4 7 -c 160000 blind_white.mat glazing.rad blind1.rad > blind12.xml
183			.SH NOTES
184			The variable resolution (tensor tree) BSDF representation is not supported
185			by all software and applicatons, and should be used with caution.
186			It provides practical, high-resolution data for use in the
187			Radiance rendering programs, but does not work in the matrix formulation
188			of the daylight coefficient method for example.
189			Also, third party tools generally expect or require a fixed number of sample
190			directions using the Klems directions or similar.
191	greg	1.1	.SH AUTHOR
192			Greg Ward
193			.SH "SEE ALSO"
194	greg	1.13	dctimestep(1), gendaymtx(1), genklemsamp(1), genskyvec(1), mkillum(1),
195	greg	1.16	pkgBSDF(1), rcontrib(1), rfluxmtx(1), rmtxop(1), rtrace(1) wrapBSDF(1)