man/man1/bsdf2ttree.1

.\" RCSid $Id: bsdf2ttree.1,v 1.3 2013/09/26 17:05:00 greg Exp $
.TH BSDF2TTREE 1 4/24/2013 RADIANCE
.SH NAME
bsdf2ttree - generate XML tensor tree description of a BSDF
.SH SYNOPSIS
.B bsdf2ttree
[
.B "\-pC"
][
.B "\-g Nlog2"
][
.B "\-t pctcull"
][
.B "\-l maxlobes"
]
[
.B "bsdf.sir .."
]
.br
or
.br
.B bsdf2ttree
.B "\-t{3|4}"
[
.B "\-pC"
][
.B "\-g Nlog2"
][
.B "\-t pctcull"
][
.B "{+|-}forward"
][
.B "{+|-}backward"
][
.B "\-e expr"
][
.B "\-f file"
]
.B bsdf_func
.SH DESCRIPTION
.I Bsdf2ttree
produces a tensor tree representation of a
bidirectional scattering distribution function (BSDF)
based on an intermediate representation (in the first form) or
a functional description (in the second form).
A complete XML description is written to the standard output,
which is normally redirected to a file.
.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 maximum resolution of the tensor tree may be controlled by the
.I \-g
option, which defaults to a value of 6.
This corresponds to a peak resolution of 2^6 (64) in each dimension.
Due to memory and time constraints, it is not recommended to set
.I \-g
higher than 7, which corresponds to a 128x128x128x128 initial sampling,
or 268 million values.
.PP
The initial sampling is pared down by the percentage specified with the
.I \-t
option, which defaults to 90.
Setting this parameter to -1 turns culling off entirely, which may be
useful for comparisons.
.PP
The first invocation form takes a intermediate scattering representation
as produced by
.I pabopto2bsdf(1)
or similar, and produces a tensor tree 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.
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
In the second invocation form,
.I bsdf2ttree
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.
If the
.I \-t3
option is specified, the defined function is assumed to be isotropic.
If the
.I \-t4
option is given, the function is assumed to be anisotropic.
.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 high-resolution tensor tree with 85% culling:
.IP "" .2i
bsdf2ttree -g 7 -t 85 transmitted.sir reflected.sir > combined.xml
.PP
To create a low-res BSDF corresponding to a one-sided,
isotropic Phong distribution:
.IP "" .2i
bsdf2ttree -g 5 -t3 -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"
bsdf2klems(1), icalc(1), genBSDF(1), pkgBSDF(1)
Revision:	1.4
Committed:	Wed Mar 12 21:15:31 2014 UTC (11 years, 7 months ago) by greg
Branch:	MAIN
CVS Tags:	rad4R2P2, rad4R2P1, rad4R2
Changes since 1.3:	+11 -1 lines
Log Message:	Disabled DEBUG statements in BSDF programs and added progress bars
#	User	Rev	Content
1	greg	1.4	.\" RCSid $Id: bsdf2ttree.1,v 1.3 2013/09/26 17:05:00 greg Exp $
2	greg	1.1	.TH BSDF2TTREE 1 4/24/2013 RADIANCE
3			.SH NAME
4			bsdf2ttree - generate XML tensor tree description of a BSDF
5			.SH SYNOPSIS
6			.B bsdf2ttree
7			[
8	greg	1.4	.B "\-pC"
9			][
10	greg	1.1	.B "\-g Nlog2"
11			][
12	greg	1.3	.B "\-t pctcull"
13			][
14			.B "\-l maxlobes"
15	greg	1.1	]
16			[
17			.B "bsdf.sir .."
18			]
19			.br
20			or
21			.br
22			.B bsdf2ttree
23			.B "\-t{3\|4}"
24			[
25	greg	1.4	.B "\-pC"
26			][
27	greg	1.1	.B "\-g Nlog2"
28			][
29	greg	1.3	.B "\-t pctcull"
30	greg	1.1	][
31			.B "{+\|-}forward"
32			][
33			.B "{+\|-}backward"
34			][
35	greg	1.3	.B "\-e expr"
36	greg	1.1	][
37	greg	1.3	.B "\-f file"
38	greg	1.1	]
39			.B bsdf_func
40			.SH DESCRIPTION
41			.I Bsdf2ttree
42			produces a tensor tree representation of a
43			bidirectional scattering distribution function (BSDF)
44			based on an intermediate representation (in the first form) or
45			a functional description (in the second form).
46			A complete XML description is written to the standard output,
47			which is normally redirected to a file.
48			.PP
49	greg	1.4	The
50			.I \-p
51			option by itself turns off the progress bar, whose length may be set
52			by an immediately following integer argument.
53			(The default progress bar length is 79 characters.)\0
54			.PP
55	greg	1.1	The maximum resolution of the tensor tree may be controlled by the
56			.I \-g
57			option, which defaults to a value of 6.
58			This corresponds to a peak resolution of 2^6 (64) in each dimension.
59			Due to memory and time constraints, it is not recommended to set
60			.I \-g
61			higher than 7, which corresponds to a 128x128x128x128 initial sampling,
62			or 268 million values.
63			.PP
64			The initial sampling is pared down by the percentage specified with the
65			.I \-t
66			option, which defaults to 90.
67			Setting this parameter to -1 turns culling off entirely, which may be
68			useful for comparisons.
69			.PP
70			The first invocation form takes a intermediate scattering representation
71			as produced by
72			.I pabopto2bsdf(1)
73			or similar, and produces a tensor tree representation with as many
74			components as there are independent input distributions.
75			Each intermediate scattering file contains one of
76			the four components, and if the first component
77			is isotropic, all components must be isotropic.
78			A similar rule holds for anisotropic inputs.
79	greg	1.3	The
80			.I \-l
81			option may be used to specify the maximum number of lobes in any
82			interpolated radial basis function.
83			The default value is 15000, which generally keeps the interpolation tractable.
84			Setting the value to 0 turns off this limit.
85	greg	1.1	.PP
86			In the second invocation form,
87			.I bsdf2ttree
88			takes a functional specification of a BSDF.
89	greg	1.2	The named function should accept 6 parameters corresponding to the
90	greg	1.1	normalized incident and exiting vectors, respectively.
91			By convention, these vectors point away from the surface, and a positive
92			Z-component corresponds to the front side.
93			The Y-component corresponds to the "up" orientation of the surface,
94			as specified in the eventual scene description that references the XML
95			output.
96	greg	1.2	If the function only takes 3 parameters, then the variables "Dx", "Dy",
97			and "Dz" will be assigned to the reverse of the outgoing direction at
98			each evaluation.
99			(I.e., the vector will point into the surface and
100			Dz will be negative on the front side.)\0
101			This simplifies conversion of functional BSDF specifications using the
102			legacy material primitives "plasfunc", "metfunc", and "transfunc".
103	greg	1.1	.PP
104			The function is defined by one or more
105			.I \-e
106			and
107			.I \-f
108			options, and should obey both Helmholtz reciprocity and
109			integrate to less than 1 over each projected incident hemisphere
110			for energy conservation.
111			If the
112			.I \-t3
113			option is specified, the defined function is assumed to be isotropic.
114			If the
115			.I \-t4
116			option is given, the function is assumed to be anisotropic.
117			.PP
118			Similar to the
119			.I genBSDF(1)
120			command,
121			the
122			.I \+backward
123			option (default) specifies that rays arriving from the front side of
124			the surface will be tested for reflection and transmission.
125			If both forward and backward (front and back) distributions are needed, the
126			.I \+forward
127			option may be given.
128			To turn off the backward components, use the
129			.I \-backward
130			option.
131			Computing both incident hemispheres takes about twice as long as one, but
132			is recommended when rays will be impinging from either side.
133			.SH EXAMPLE
134			To take two components of an intermediate BSDF representation and create
135			a high-resolution tensor tree with 85% culling:
136			.IP "" .2i
137			bsdf2ttree -g 7 -t 85 transmitted.sir reflected.sir > combined.xml
138			.PP
139			To create a low-res BSDF corresponding to a one-sided,
140			isotropic Phong distribution:
141			.IP "" .2i
142			bsdf2ttree -g 5 -t3 -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
143			.SH AUTHOR
144			Greg Ward
145			.SH "SEE ALSO"
146			bsdf2klems(1), icalc(1), genBSDF(1), pkgBSDF(1)