man/man1/bsdf2klems.1

.\" RCSid $Id: bsdf2klems.1,v 1.7 2019/03/19 22:03:24 greg Exp $
.TH BSDF2KLEMS 1 4/24/2013 RADIANCE
.SH NAME
bsdf2klems - generate XML Klems matrix description of a BSDF
.SH SYNOPSIS
.B bsdf2klems
[
.B "\-n spp"
][
.B "\-h|\-q"
][
.B "\-pC"
][
.B "\-l maxlobes"
]
[
.B "bsdf.sir .."
]
.br
or
.br
.B bsdf2klems
[
.B "\-n spp"
][
.B "\-h|\-q"
][
.B "\-pC"
]
.B bsdf_in.xml
.br
or
.br
.B bsdf2klems
[
.B "\-n spp"
][
.B "\-h|\-q"
][
.B "\-pC"
][
.B "{+|-}forward"
][
.B "{+|-}backward"
][
.B "\-e expr"
][
.B "\-f file"
]
.B bsdf_func
.SH DESCRIPTION
.I Bsdf2klems
produces a Klems matrix representation of a
bidirectional scattering distribution function (BSDF)
based on an intermediate representation (in the first form),
an input XML representation (in the second form),
or a functional description (in the third form).
A complete XML description is written to the standard output,
which is normally redirected to a file.
.PP
The Klems matrix representation divides the input and output
hemisphere into a default 145 patches.
The
.I \-h
option may be used to reduce this number to 73 patches per hemisphere.
The
.I \-q
option may be used to reduce this number to 41 patches.
Neither option is recommended unless the distribution is known to
be approximately diffuse.
.PP
The
.I \-p
option by itself turns off the progress bar, whose length may be set
by an immediately following integer argument.
(The default progress bar length is 79 characters.)\0
.PP
The
.I \-l
option may be used to specify the maximum number of lobes in any
interpolated radial basis function.
The default value is 15000, which generally keeps the interpolation tractable.
Setting the value to 0 turns off this limit.
.PP
Normally, multiple samples are taken from random points on each input
and output patch to improve accuracy.
The number of samples to take for each input-output patch pair may
be controlled using the
.I \-n
option, which defaults to 1024.
.PP
The first invocation form takes a intermediate scattering representation
as produced by
.I pabopto2bsdf(1)
or similar, and produces a Klems representation with as many
components as there are independent input distributions.
Each intermediate scattering file contains one of
the four components, and if the first component
is isotropic, all components must be isotropic.
A similar rule holds for anisotropic inputs.
Only the center of each incident patches is sampled, due to
the time required to interpolate incident positions.
.PP
In the second invocation form, an input XML representation
is resampled to produce the desired Klems matrix representation.
This is primarily used to convert a tensor tree representation
into a matrix for annual daylighting simulations.
Any components in the input are reproduced on output, and inline
geometric descriptions are passed unchanged.
.PP
In the third invocation form,
.I bsdf2klems
takes a functional specification of a BSDF.
The named function should accept 6 parameters corresponding to the
normalized incident and exiting vectors, respectively.
By convention, these vectors point away from the surface, and a positive
Z-component corresponds to the front side.
The Y-component corresponds to the "up" orientation of the surface,
as specified in the eventual scene description that references the XML
output.
If the function only takes 3 parameters, then the variables "Dx", "Dy",
and "Dz" will be assigned to the reverse of the outgoing direction at
each evaluation.
(I.e., the vector will point into the surface and
Dz will be negative on the front side.)\0
This simplifies conversion of functional BSDF specifications using the
legacy material primitives "plasfunc", "metfunc", and "transfunc".
.PP
The function is defined by one or more
.I \-e
and
.I \-f
options, and should obey both Helmholtz reciprocity and
integrate to less than 1 over each projected incident hemisphere
for energy conservation.
The variable and function definitions in each
.I \-f source
file are read and compiled from the RADIANCE library where it is found.
.PP
Similar to the
.I genBSDF(1)
command,
the
.I \+backward
option (default) specifies that rays arriving from the front side of
the surface will be tested for reflection and transmission.
If both forward and backward (front and back) distributions are needed, the
.I \+forward
option may be given.
To turn off the backward components, use the
.I \-backward
option.
Computing both incident hemispheres takes about twice as long as one, but
is recommended when rays will be impinging from either side.
.SH EXAMPLE
To take two components of an intermediate BSDF representation and create
a full Klems matrix representation:
.IP "" .2i
bsdf2klems transmitted.sir reflected.sir > combined.xml
.PP
To reduce a tensor tree representation into a half-Klems matrix representation:
.IP "" .2i
bsdf2klems -h ttree.xml > klems_half.xml
.PP
To create a low-res BSDF corresponding to a one-sided,
isotropic Phong distribution:
.IP "" .2i
bsdf2klems -e 'phong(ix,iy,iz,ox,oy,oz) = if(iz, .1+((iz+oz)/sqrt((ix+ox)^2+(iy+oy)^2+(iz+oz)^2))^50, 0)' phong > phong.xml
.SH ENVIRONMENT
RAYPATH         the directories to check for auxiliary files.
.SH AUTHOR
Greg Ward
.SH "SEE ALSO"
bsdf2ttree(1), dctimestep(1), icalc(1), gendaymtx(1), genklemsamp(1),
genskyvec(1), mkillum(1), genBSDF(1), pabopto2bsdf(1), pabopto2xyz(1),
pkgBSDF(1), rcontrib(1), rfluxmtx(1), rmtxop(1), wrapBSDF(1)
Revision:	1.8
Committed:	Thu Feb 25 04:48:19 2021 UTC (4 years, 2 months ago) by greg
Branch:	MAIN
CVS Tags:	rad5R4, HEAD
Changes since 1.7:	+3 -3 lines
Log Message:	docs: added man page for pabopto2bsdf
#	Content
1	.\" RCSid $Id: bsdf2klems.1,v 1.7 2019/03/19 22:03:24 greg Exp $
2	.TH BSDF2KLEMS 1 4/24/2013 RADIANCE
3	.SH NAME
4	bsdf2klems - generate XML Klems matrix description of a BSDF
5	.SH SYNOPSIS
6	.B bsdf2klems
7	[
8	.B "\-n spp"
9	][
10	.B "\-h\|\-q"
11	][
12	.B "\-pC"
13	][
14	.B "\-l maxlobes"
15	]
16	[
17	.B "bsdf.sir .."
18	]
19	.br
20	or
21	.br
22	.B bsdf2klems
23	[
24	.B "\-n spp"
25	][
26	.B "\-h\|\-q"
27	][
28	.B "\-pC"
29	]
30	.B bsdf_in.xml
31	.br
32	or
33	.br
34	.B bsdf2klems
35	[
36	.B "\-n spp"
37	][
38	.B "\-h\|\-q"
39	][
40	.B "\-pC"
41	][
42	.B "{+\|-}forward"
43	][
44	.B "{+\|-}backward"
45	][
46	.B "\-e expr"
47	][
48	.B "\-f file"
49	]
50	.B bsdf_func
51	.SH DESCRIPTION
52	.I Bsdf2klems
53	produces a Klems matrix representation of a
54	bidirectional scattering distribution function (BSDF)
55	based on an intermediate representation (in the first form),
56	an input XML representation (in the second form),
57	or a functional description (in the third form).
58	A complete XML description is written to the standard output,
59	which is normally redirected to a file.
60	.PP
61	The Klems matrix representation divides the input and output
62	hemisphere into a default 145 patches.
63	The
64	.I \-h
65	option may be used to reduce this number to 73 patches per hemisphere.
66	The
67	.I \-q
68	option may be used to reduce this number to 41 patches.
69	Neither option is recommended unless the distribution is known to
70	be approximately diffuse.
71	.PP
72	The
73	.I \-p
74	option by itself turns off the progress bar, whose length may be set
75	by an immediately following integer argument.
76	(The default progress bar length is 79 characters.)\0
77	.PP
78	The
79	.I \-l
80	option may be used to specify the maximum number of lobes in any
81	interpolated radial basis function.
82	The default value is 15000, which generally keeps the interpolation tractable.
83	Setting the value to 0 turns off this limit.
84	.PP
85	Normally, multiple samples are taken from random points on each input
86	and output patch to improve accuracy.
87	The number of samples to take for each input-output patch pair may
88	be controlled using the
89	.I \-n
90	option, which defaults to 1024.
91	.PP
92	The first invocation form takes a intermediate scattering representation
93	as produced by
94	.I pabopto2bsdf(1)
95	or similar, and produces a Klems representation with as many
96	components as there are independent input distributions.
97	Each intermediate scattering file contains one of
98	the four components, and if the first component
99	is isotropic, all components must be isotropic.
100	A similar rule holds for anisotropic inputs.
101	Only the center of each incident patches is sampled, due to
102	the time required to interpolate incident positions.
103	.PP
104	In the second invocation form, an input XML representation
105	is resampled to produce the desired Klems matrix representation.
106	This is primarily used to convert a tensor tree representation
107	into a matrix for annual daylighting simulations.
108	Any components in the input are reproduced on output, and inline
109	geometric descriptions are passed unchanged.
110	.PP
111	In the third invocation form,
112	.I bsdf2klems
113	takes a functional specification of a BSDF.
114	The named function should accept 6 parameters corresponding to the
115	normalized incident and exiting vectors, respectively.
116	By convention, these vectors point away from the surface, and a positive
117	Z-component corresponds to the front side.
118	The Y-component corresponds to the "up" orientation of the surface,
119	as specified in the eventual scene description that references the XML
120	output.
121	If the function only takes 3 parameters, then the variables "Dx", "Dy",
122	and "Dz" will be assigned to the reverse of the outgoing direction at
123	each evaluation.
124	(I.e., the vector will point into the surface and
125	Dz will be negative on the front side.)\0
126	This simplifies conversion of functional BSDF specifications using the
127	legacy material primitives "plasfunc", "metfunc", and "transfunc".
128	.PP
129	The function is defined by one or more
130	.I \-e
131	and
132	.I \-f
133	options, and should obey both Helmholtz reciprocity and
134	integrate to less than 1 over each projected incident hemisphere
135	for energy conservation.
136	The variable and function definitions in each
137	.I \-f source
138	file are read and compiled from the RADIANCE library where it is found.
139	.PP
140	Similar to the
141	.I genBSDF(1)
142	command,
143	the
144	.I \+backward
145	option (default) specifies that rays arriving from the front side of
146	the surface will be tested for reflection and transmission.
147	If both forward and backward (front and back) distributions are needed, the
148	.I \+forward
149	option may be given.
150	To turn off the backward components, use the
151	.I \-backward
152	option.
153	Computing both incident hemispheres takes about twice as long as one, but
154	is recommended when rays will be impinging from either side.
155	.SH EXAMPLE
156	To take two components of an intermediate BSDF representation and create
157	a full Klems matrix representation:
158	.IP "" .2i
159	bsdf2klems transmitted.sir reflected.sir > combined.xml
160	.PP
161	To reduce a tensor tree representation into a half-Klems matrix representation:
162	.IP "" .2i
163	bsdf2klems -h ttree.xml > klems_half.xml
164	.PP
165	To create a low-res BSDF corresponding to a one-sided,
166	isotropic Phong distribution:
167	.IP "" .2i
168	bsdf2klems -e 'phong(ix,iy,iz,ox,oy,oz) = if(iz, .1+((iz+oz)/sqrt((ix+ox)^2+(iy+oy)^2+(iz+oz)^2))^50, 0)' phong > phong.xml
169	.SH ENVIRONMENT
170	RAYPATH the directories to check for auxiliary files.
171	.SH AUTHOR
172	Greg Ward
173	.SH "SEE ALSO"
174	bsdf2ttree(1), dctimestep(1), icalc(1), gendaymtx(1), genklemsamp(1),
175	genskyvec(1), mkillum(1), genBSDF(1), pabopto2bsdf(1), pabopto2xyz(1),
176	pkgBSDF(1), rcontrib(1), rfluxmtx(1), rmtxop(1), wrapBSDF(1)