man/man1/bsdf2klems.1

.\" RCSid $Id$
.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 "bsdf.sir .."
]
.br
or
.br
.B bsdf2klems
[
.B "\-n spp"
][
.B "\-h|\-q"
]
.B bsdf_in.xml
.br
or
.br
.B bsdf2klems
[
.B "\-n spp"
][
.B "\-h|\-q"
][
.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
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 256.
.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 must 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.
.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.
.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 AUTHOR
Greg Ward
.SH "SEE ALSO"
bsdf2ttree(1), dctimestep(1), icalc(1), gendaymtx(1), genklemsamp(1),
genskyvec(1), mkillum(1), genBSDF(1), pkgBSDF(1), rcontrib(1), rtrace(1)
Revision:	1.1
Committed:	Thu Apr 25 00:43:20 2013 UTC (12 years, 1 month ago) by greg
Branch:	MAIN
Log Message:	Created man pages for bsdf2klems and bsdf2ttree
#	Content
1	.\" RCSid $Id$
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	[
13	.B "bsdf.sir .."
14	]
15	.br
16	or
17	.br
18	.B bsdf2klems
19	[
20	.B "\-n spp"
21	][
22	.B "\-h\|\-q"
23	]
24	.B bsdf_in.xml
25	.br
26	or
27	.br
28	.B bsdf2klems
29	[
30	.B "\-n spp"
31	][
32	.B "\-h\|\-q"
33	][
34	.B "{+\|-}forward"
35	][
36	.B "{+\|-}backward"
37	][
38	.B "\-e expr
39	][
40	.B "\-f file
41	]
42	.B bsdf_func
43	.SH DESCRIPTION
44	.I Bsdf2klems
45	produces a Klems matrix representation of a
46	bidirectional scattering distribution function (BSDF)
47	based on an intermediate representation (in the first form),
48	an input XML representation (in the second form),
49	or a functional description (in the third form).
50	A complete XML description is written to the standard output,
51	which is normally redirected to a file.
52	.PP
53	The Klems matrix representation divides the input and output
54	hemisphere into a default 145 patches.
55	The
56	.I \-h
57	option may be used to reduce this number to 73 patches per hemisphere.
58	The
59	.I \-q
60	option may be used to reduce this number to 41 patches.
61	Neither option is recommended unless the distribution is known to
62	be approximately diffuse.
63	.PP
64	Normally, multiple samples are taken from random points on each input
65	and output patch to improve accuracy.
66	The number of samples to take for each input-output patch pair may
67	be controlled using the
68	.I \-n
69	option, which defaults to 256.
70	.PP
71	The first invocation form takes a intermediate scattering representation
72	as produced by
73	.I pabopto2bsdf(1)
74	or similar, and produces a Klems representation with as many
75	components as there are independent input distributions.
76	Each intermediate scattering file contains one of
77	the four components, and if the first component
78	is isotropic, all components must be isotropic.
79	A similar rule holds for anisotropic inputs.
80	Only the center of each incident patches is sampled, due to
81	the time required to interpolate incident positions.
82	.PP
83	In the second invocation form, an input XML representation
84	is resampled to produce the desired Klems matrix representation.
85	This is primarily used to convert a tensor tree representation
86	into a matrix for annual daylighting simulations.
87	Any components in the input are reproduced on output, and inline
88	geometric descriptions are passed unchanged.
89	.PP
90	In the third invocation form,
91	.I bsdf2klems
92	takes a functional specification of a BSDF.
93	The named function must accept 6 parameters corresponding to the
94	normalized incident and exiting vectors, respectively.
95	By convention, these vectors point away from the surface, and a positive
96	Z-component corresponds to the front side.
97	The Y-component corresponds to the "up" orientation of the surface,
98	as specified in the eventual scene description that references the XML
99	output.
100	.PP
101	The function is defined by one or more
102	.I \-e
103	and
104	.I \-f
105	options, and should obey both Helmholtz reciprocity and
106	integrate to less than 1 over each projected incident hemisphere
107	for energy conservation.
108	.PP
109	Similar to the
110	.I genBSDF(1)
111	command,
112	the
113	.I \+backward
114	option (default) specifies that rays arriving from the front side of
115	the surface will be tested for reflection and transmission.
116	If both forward and backward (front and back) distributions are needed, the
117	.I \+forward
118	option may be given.
119	To turn off the backward components, use the
120	.I \-backward
121	option.
122	Computing both incident hemispheres takes about twice as long as one, but
123	is recommended when rays will be impinging from either side.
124	.SH EXAMPLE
125	To take two components of an intermediate BSDF representation and create
126	a full Klems matrix representation:
127	.IP "" .2i
128	bsdf2klems transmitted.sir reflected.sir > combined.xml
129	.PP
130	To reduce a tensor tree representation into a half-Klems matrix representation:
131	.IP "" .2i
132	bsdf2klems -h ttree.xml > klems_half.xml
133	.PP
134	To create a low-res BSDF corresponding to a one-sided,
135	isotropic Phong distribution:
136	.IP "" .2i
137	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
138	.SH AUTHOR
139	Greg Ward
140	.SH "SEE ALSO"
141	bsdf2ttree(1), dctimestep(1), icalc(1), gendaymtx(1), genklemsamp(1),
142	genskyvec(1), mkillum(1), genBSDF(1), pkgBSDF(1), rcontrib(1), rtrace(1)