| 1 |
< |
.\" RCSid "$Id" |
| 1 |
> |
.\" RCSid "$Id$" |
| 2 |
|
.\" Print using the -ms macro package |
| 3 |
< |
.DA 10/26/2011 |
| 3 |
> |
.DA 11/13/2023 |
| 4 |
|
.LP |
| 5 |
< |
.tl """Copyright \(co 2011 Regents, University of California |
| 5 |
> |
.tl """Copyright \(co 2023 Regents, University of California |
| 6 |
|
.sp 2 |
| 7 |
|
.TL |
| 8 |
|
The |
| 622 |
|
8 red green blue spec urough vrough trans tspec |
| 623 |
|
.DE |
| 624 |
|
.LP |
| 625 |
+ |
.UL Ashik2 |
| 626 |
+ |
.PP |
| 627 |
+ |
Ashik2 is the anisotropic reflectance model by Ashikhmin & Shirley. |
| 628 |
+ |
The string arguments are the same as for plastic2, but the real |
| 629 |
+ |
arguments have additional flexibility to specify the specular color. |
| 630 |
+ |
Also, rather than roughness, specular power is used, which has no |
| 631 |
+ |
physical meaning other than larger numbers are equivalent to a smoother |
| 632 |
+ |
surface. |
| 633 |
+ |
Unlike other material types, total reflectance is the sum of |
| 634 |
+ |
diffuse and specular colors, and should be adjusted accordingly. |
| 635 |
+ |
.DS |
| 636 |
+ |
mod ashik2 id |
| 637 |
+ |
4+ ux uy uz funcfile transform |
| 638 |
+ |
0 |
| 639 |
+ |
8 dred dgrn dblu sred sgrn sblu u-power v-power |
| 640 |
+ |
.DE |
| 641 |
+ |
.LP |
| 642 |
|
.UL Dielectric |
| 643 |
|
.PP |
| 644 |
|
A dielectric material is transparent, and it refracts light |
| 949 |
|
Unlike other data-driven material types, the BSDF type is fully |
| 950 |
|
supported and all parts of the distribution are properly sampled. |
| 951 |
|
.LP |
| 952 |
+ |
.UL aBSDF |
| 953 |
+ |
.PP |
| 954 |
+ |
The aBSDF material is identical to the BSDF type with two important |
| 955 |
+ |
differences. |
| 956 |
+ |
First, proxy geometry is not supported, so there is no thickness parameter. |
| 957 |
+ |
Second, an aBSDF is assumed to have some specular through component |
| 958 |
+ |
(the 'a' stands for "aperture"), which |
| 959 |
+ |
is treated specially during the direct calculation and when viewing the |
| 960 |
+ |
material. |
| 961 |
+ |
Based on the BSDF data, the coefficient of specular transmission is |
| 962 |
+ |
determined and used for modifying unscattered shadow and view rays. |
| 963 |
+ |
.DS |
| 964 |
+ |
mod aBSDF id |
| 965 |
+ |
5+ BSDFfile ux uy uz funcfile transform |
| 966 |
+ |
0 |
| 967 |
+ |
0|3|6|9 |
| 968 |
+ |
rfdif gfdif bfdif |
| 969 |
+ |
rbdif gbdif bbdif |
| 970 |
+ |
rtdif gtdif btdif |
| 971 |
+ |
.DE |
| 972 |
+ |
.LP |
| 973 |
+ |
If a material has no specular transmitted component, it is much better |
| 974 |
+ |
to use the BSDF type with a zero thickness than to use aBSDF. |
| 975 |
+ |
.LP |
| 976 |
|
.UL Antimatter |
| 977 |
|
.PP |
| 978 |
|
Antimatter is a material that can "subtract" volumes from other volumes. |
| 987 |
|
The first modifier will also be used to shade the area leaving the |
| 988 |
|
antimatter volume and entering the regular volume. |
| 989 |
|
If mod1 is void, the antimatter volume is completely invisible. |
| 990 |
< |
Antimatter does not work properly with the material type "trans", |
| 991 |
< |
and multiple antimatter surfaces should be disjoint. |
| 990 |
> |
If shading is desired at antimatter surfaces, it is important |
| 991 |
> |
that the related volumes are closed with outward-facing normals. |
| 992 |
> |
Antimatter surfaces should not intersect with other antimatter boundaries, |
| 993 |
> |
and it is unwise to use the same modifier in nested antimatter volumes. |
| 994 |
|
The viewpoint must be outside all volumes concerned for a correct |
| 995 |
|
rendering. |
| 996 |
|
.NH 3 |
| 1194 |
|
font such as hexbit4x1.fnt, calls for uniform spacing. |
| 1195 |
|
Reasonable magnitudes for proportional spacing are |
| 1196 |
|
between 0.1 (for tightly spaced characters) and 0.3 (for wide spacing). |
| 1197 |
+ |
.LP |
| 1198 |
+ |
.UL Spectrum |
| 1199 |
+ |
.PP |
| 1200 |
+ |
The spectrum primitive is the most basic type for introducing spectral |
| 1201 |
+ |
color to a material. |
| 1202 |
+ |
Since materials only provide RGB parameters, spectral patterns |
| 1203 |
+ |
are the only way to superimpose wavelength-dependent behavior. |
| 1204 |
+ |
.DS |
| 1205 |
+ |
mod spectrum id |
| 1206 |
+ |
0 |
| 1207 |
+ |
0 |
| 1208 |
+ |
5+ nmA nmB s1 s2 .. sN |
| 1209 |
+ |
.DE |
| 1210 |
+ |
The first two real arguments indicate the limits of the covered |
| 1211 |
+ |
spectral range in nanometers. |
| 1212 |
+ |
Subsequent real values correspond to multipliers in each wavelength band, |
| 1213 |
+ |
where the first band goes from nmA to nmA+(nmB-nmA)/N, and N is the |
| 1214 |
+ |
number of bands (i.e., the number of real arguments minus 2). |
| 1215 |
+ |
The nmA wavelength may be greater or less than nmB, |
| 1216 |
+ |
but they may not be equal, and their ordering matches |
| 1217 |
+ |
the order of the spectral values. |
| 1218 |
+ |
A minimum of 3 values must be given, which would act |
| 1219 |
+ |
more or less the same as a constant RGB multiplier. |
| 1220 |
+ |
As with RGB values, spectral quantities normally range between 0 |
| 1221 |
+ |
and 1 at each wavelength, or average to 1.0 against a standard |
| 1222 |
+ |
sensitivity functions such as V(lambda). |
| 1223 |
+ |
The best results obtain when the spectral range and number |
| 1224 |
+ |
of samples match rendering options, though resampling will handle |
| 1225 |
+ |
any differences, zero-filling wavelenths outside the nmA to nmB |
| 1226 |
+ |
range. |
| 1227 |
+ |
A warning will be issued if the given wavelength range does not |
| 1228 |
+ |
adequately cover the visible spectrum. |
| 1229 |
+ |
.LP |
| 1230 |
+ |
.UL Specfile |
| 1231 |
+ |
.PP |
| 1232 |
+ |
The specfile primitive is equivalent to the spectrum type, but |
| 1233 |
+ |
the wavelength range and values are contained in a 1-dimensional |
| 1234 |
+ |
data file. |
| 1235 |
+ |
This may be a more convenient way to specify a spectral color, |
| 1236 |
+ |
especially one corresponding to a standard illuminant such as D65 |
| 1237 |
+ |
or a library of measured spectra. |
| 1238 |
+ |
.DS |
| 1239 |
+ |
mod specfile id |
| 1240 |
+ |
1 datafile |
| 1241 |
+ |
0 |
| 1242 |
+ |
0 |
| 1243 |
+ |
.DE |
| 1244 |
+ |
As with the spectrum type, rendering wavelengths outside the defined |
| 1245 |
+ |
range will be zero-filled. |
| 1246 |
+ |
Unlike the spectrum type, the file may contain non-uniform samples. |
| 1247 |
+ |
.LP |
| 1248 |
+ |
.UL Specfunc |
| 1249 |
+ |
.PP |
| 1250 |
+ |
The specfunc primitive offers dynamic control over a spectral |
| 1251 |
+ |
pattern, similar to the colorfunc type. |
| 1252 |
+ |
.DS |
| 1253 |
+ |
mod specfunc id |
| 1254 |
+ |
2+ sval funcfile transform |
| 1255 |
+ |
0 |
| 1256 |
+ |
2+ nmA nmB A3 .. |
| 1257 |
+ |
.DE |
| 1258 |
+ |
Like the spectrum primitive, the wavelength range is specified |
| 1259 |
+ |
in the first two real arguments, and additional real values are |
| 1260 |
+ |
accessible to the sval function. |
| 1261 |
+ |
This function is fed a wavelenth sample |
| 1262 |
+ |
between nmA and nmB as its only argument, |
| 1263 |
+ |
and it returns the corresponding spectral intensity. |
| 1264 |
|
.NH 3 |
| 1265 |
|
Mixtures |
| 1266 |
|
.PP |
| 1267 |
|
A mixture is a blend of one or more materials or textures and patterns. |
| 1268 |
+ |
Blended materials should not be light source types or virtual source types. |
| 1269 |
|
The basic types are given below. |
| 1270 |
|
.LP |
| 1271 |
|
.UL Mixfunc |
| 1662 |
|
in Lausanne, Switzerland. |
| 1663 |
|
.NH 1 |
| 1664 |
|
References |
| 1665 |
+ |
.LP |
| 1666 |
+ |
Ward, Gregory J., Bruno Bueno, David Geisler-Moroder, |
| 1667 |
+ |
Lars O. Grobe, Jacob C. Jonsson, Eleanor |
| 1668 |
+ |
S. Lee, Taoning Wang, Helen Rose Wilson, |
| 1669 |
+ |
``Daylight Simulation Workflows Incorporating |
| 1670 |
+ |
Measured Bidirectional Scattering Distribution Functions,'' |
| 1671 |
+ |
.I "Energy & Buildings", |
| 1672 |
+ |
Vol. 259, No. 111890, 2022. |
| 1673 |
+ |
.LP |
| 1674 |
+ |
Wang, Taoning, Gregory Ward, Eleanor Lee, |
| 1675 |
+ |
``Efficient modeling of optically-complex, non-coplanar |
| 1676 |
+ |
exterior shading: Validation of matrix algebraic methods,'' |
| 1677 |
+ |
.I "Energy & Buildings", |
| 1678 |
+ |
vol. 174, pp. 464-83, Sept. 2018. |
| 1679 |
+ |
.LP |
| 1680 |
+ |
Lee, Eleanor S., David Geisler-Moroder, Gregory Ward, |
| 1681 |
+ |
``Modeling the direct sun component in buildings using matrix |
| 1682 |
+ |
algebraic approaches: Methods and validation,'' |
| 1683 |
+ |
.I Solar Energy, |
| 1684 |
+ |
vol. 160, 15 January 2018, pp 380-395. |
| 1685 |
+ |
.LP |
| 1686 |
+ |
Ward, G., M. Kurt & N. Bonneel, |
| 1687 |
+ |
``Reducing Anisotropic BSDF Measurement to Common Practice,'' |
| 1688 |
+ |
.I Workshop on Material Appearance Modeling, |
| 1689 |
+ |
2014. |
| 1690 |
+ |
.LP |
| 1691 |
+ |
McNeil, A., C.J. Jonsson, D. Appelfeld, G. Ward, E.S. Lee, |
| 1692 |
+ |
``A validation of a ray-tracing tool used to generate |
| 1693 |
+ |
bi-directional scattering distribution functions for |
| 1694 |
+ |
complex fenestration systems,'' |
| 1695 |
+ |
.I "Solar Energy", |
| 1696 |
+ |
98, 404-14, November 2013. |
| 1697 |
|
.LP |
| 1698 |
|
Ward, G., R. Mistrick, E.S. Lee, A. McNeil, J. Jonsson, |
| 1699 |
|
``Simulating the Daylight Performance of Complex Fenestration Systems |
