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Revision 1.1 by greg, Thu Apr 25 00:43:20 2013 UTC vs.
Revision 1.10 by greg, Thu Feb 25 04:48:19 2021 UTC

# Line 5 | Line 5 | bsdf2ttree - generate XML tensor tree description of a
5   .SH SYNOPSIS
6   .B bsdf2ttree
7   [
8 + .B "\-pC"
9 + ][
10 + .B "{+|-}a"
11 + ][
12   .B "\-g Nlog2"
13   ][
14 < .B "\-t pctcull
15 < ]
16 < [
14 > .B "\-t pctcull"
15 > ][
16 > .B "\-n nss"
17 > ][
18 > .B "\-s thresh"
19 > ][
20 > .B "\-l maxlobes"
21 > ][
22   .B "bsdf.sir .."
23   ]
24   .br
# Line 18 | Line 27 | or
27   .B bsdf2ttree
28   .B "\-t{3|4}"
29   [
30 + .B "\-pC"
31 + ][
32 + .B "{+|-}a"
33 + ][
34   .B "\-g Nlog2"
35   ][
36 < .B "\-t pctcull
36 > .B "\-t pctcull"
37   ][
38 + .B "\-n nss"
39 + ][
40 + .B "\-s thresh"
41 + ][
42   .B "{+|-}forward"
43   ][
44   .B "{+|-}backward"
45   ][
46 < .B "\-e expr
46 > .B "\-e expr"
47   ][
48 < .B "\-f file
48 > .B "\-f file"
49   ]
50   .B bsdf_func
51   .SH DESCRIPTION
# Line 40 | Line 57 | a functional description (in the second form).
57   A complete XML description is written to the standard output,
58   which is normally redirected to a file.
59   .PP
60 + The
61 + .I \-p
62 + option by itself turns off the progress bar, whose length may be set
63 + by an immediately following integer argument.
64 + (The default progress bar length is 79 characters.)\0
65 + .PP
66 + The
67 + .I \-a
68 + option turns off reciprocity averaging for isotropic scattering or anisotropic reflection.
69 + Normally on (+a), this ensures that the tensor BRDF obeys Helmholtz reciprocity.
70 + However, in certain rare cases, reciprocity averaging can cause unwanted noise in the output.
71 + .PP
72   The maximum resolution of the tensor tree may be controlled by the
73   .I \-g
74   option, which defaults to a value of 6.
# Line 55 | Line 84 | option, which defaults to 90.
84   Setting this parameter to -1 turns culling off entirely, which may be
85   useful for comparisons.
86   .PP
87 + The
88 + .I \-n
89 + option controls the number of super-samples to send in patches whose
90 + difference to its neighbors exceeds some threshold.
91 + The default number of super-samples is 256.
92 + The difference threshold for super-sampling is controlled by the
93 + .I \-s
94 + option, and defaults to 0.35.
95 + .PP
96   The first invocation form takes a intermediate scattering representation
97   as produced by
98   .I pabopto2bsdf(1)
# Line 64 | Line 102 | Each intermediate scattering file contains one of
102   the four components, and if the first component
103   is isotropic, all components must be isotropic.
104   A similar rule holds for anisotropic inputs.
105 + The
106 + .I \-l
107 + option may be used to specify the maximum number of lobes in any
108 + interpolated radial basis function.
109 + The default value is 15000, which generally keeps the interpolation tractable.
110 + Setting the value to 0 turns off this limit.
111 + Parameter options may be altered between input files, in case a different
112 + resolution or culling percentage is indicated for transmission versus
113 + reflection for example.
114   .PP
115   In the second invocation form,
116   .I bsdf2ttree
117   takes a functional specification of a BSDF.
118 < The named function must accept 6 parameters corresponding to the
118 > The named function should accept 6 parameters corresponding to the
119   normalized incident and exiting vectors, respectively.
120   By convention, these vectors point away from the surface, and a positive
121   Z-component corresponds to the front side.
122   The Y-component corresponds to the "up" orientation of the surface,
123   as specified in the eventual scene description that references the XML
124   output.
125 + If the function only takes 3 parameters, then the variables "Dx", "Dy",
126 + and "Dz" will be assigned to the reverse of the outgoing direction at
127 + each evaluation.
128 + (I.e., the vector will point into the surface and
129 + Dz will be negative on the front side.)\0
130 + This simplifies conversion of functional BSDF specifications using the
131 + legacy material primitives "plasfunc", "metfunc", and "transfunc".
132   .PP
133   The function is defined by one or more
134   .I \-e
# Line 83 | Line 137 | and
137   options, and should obey both Helmholtz reciprocity and
138   integrate to less than 1 over each projected incident hemisphere
139   for energy conservation.
140 + The variable and function definitions in each
141 + .I \-f source
142 + file are read and compiled from the RADIANCE library where it is found.
143   If the
144   .I \-t3
145   option is specified, the defined function is assumed to be isotropic.
# Line 107 | Line 164 | Computing both incident hemispheres takes about twice
164   is recommended when rays will be impinging from either side.
165   .SH EXAMPLE
166   To take two components of an intermediate BSDF representation and create
167 < a high-resolution tensor tree with 85% culling:
167 > a high-resolution tensor tree with 85% culling on transmission and 95%
168 > culling on reflection:
169   .IP "" .2i
170 < bsdf2ttree -g 7 -t 85 transmitted.sir reflected.sir > combined.xml
170 > bsdf2ttree -g 7 -t 85 transmitted.sir -t 95 reflected.sir > combined.xml
171   .PP
172   To create a low-res BSDF corresponding to a one-sided,
173   isotropic Phong distribution:
174   .IP "" .2i
175   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
176 + .SH ENVIRONMENT
177 + RAYPATH         the directories to check for auxiliary files.
178   .SH AUTHOR
179   Greg Ward
180   .SH "SEE ALSO"
181 < bsdf2klems(1), icalc(1), genBSDF(1), pkgBSDF(1)
181 > bsdf2klems(1), icalc(1), genBSDF(1), pabopto2bsdf(1), pabopto2xyz(1),
182 > pkgBSDF(1), rcontrib(1), rfluxmtx(1), wrapBSDF(1)

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