| 1 |
|
.\" RCSid "$Id$" |
| 2 |
|
.\" Print using the -ms macro package |
| 3 |
< |
.DA 11/13/2023 |
| 3 |
> |
.DA 12/09/2024 |
| 4 |
|
.LP |
| 5 |
< |
.tl """Copyright \(co 2023 Regents, University of California |
| 5 |
> |
.tl """Copyright \(co 2024 Regents, University of California |
| 6 |
|
.sp 2 |
| 7 |
|
.TL |
| 8 |
|
The |
| 639 |
|
8 dred dgrn dblu sred sgrn sblu u-power v-power |
| 640 |
|
.DE |
| 641 |
|
.LP |
| 642 |
+ |
.UL WGMDfunc |
| 643 |
+ |
.PP |
| 644 |
+ |
WGMDfunc is a more programmable version of trans2, |
| 645 |
+ |
with separate modifier paths and variables to control each component. |
| 646 |
+ |
(WGMD stands for Ward-Geisler-Moroder-Duer, which is the basis for |
| 647 |
+ |
this empirical model, similar to the previous ones beside Ashik2.)\0 |
| 648 |
+ |
The specification of this material is given below. |
| 649 |
+ |
.DS |
| 650 |
+ |
mod WGMDfunc id |
| 651 |
+ |
13+ rs_mod rs rs_urough rs_vrough |
| 652 |
+ |
ts_mod ts ts_urough ts_vrough |
| 653 |
+ |
td_mod |
| 654 |
+ |
ux uy uz funcfile transform |
| 655 |
+ |
0 |
| 656 |
+ |
9+ rfdif gfdif bfdif |
| 657 |
+ |
rbdif gbdif bbdif |
| 658 |
+ |
rtdif gtdif btdif |
| 659 |
+ |
A10 .. |
| 660 |
+ |
.DE |
| 661 |
+ |
The sum of specular reflectance ( |
| 662 |
+ |
.I rs |
| 663 |
+ |
), specular transmittance ( |
| 664 |
+ |
.I ts |
| 665 |
+ |
), diffuse reflectance ( |
| 666 |
+ |
.I "rfdif gfdif bfdif" |
| 667 |
+ |
for front and |
| 668 |
+ |
.I "rbdif gbdif bbdif" |
| 669 |
+ |
for back) |
| 670 |
+ |
and diffuse transmittance ( |
| 671 |
+ |
.I "rtdif gtdif btdif" |
| 672 |
+ |
) should be less than 1 for each |
| 673 |
+ |
channel. |
| 674 |
+ |
.PP |
| 675 |
+ |
Unique to this material, separate modifier channels are |
| 676 |
+ |
provided for each component. |
| 677 |
+ |
The main modifier is used on the diffuse reflectance, both |
| 678 |
+ |
front and back. |
| 679 |
+ |
The |
| 680 |
+ |
.I rs_mod |
| 681 |
+ |
modifier is used for specular reflectance. |
| 682 |
+ |
If "void" is given for |
| 683 |
+ |
.I rs_mod, |
| 684 |
+ |
then the specular reflection color will be white. |
| 685 |
+ |
The special "inherit" keyword may also be given, in which case |
| 686 |
+ |
specular reflectance will share the main modifier. |
| 687 |
+ |
This behavior is replicated for the specular transmittance modifier |
| 688 |
+ |
.I ts_mod, |
| 689 |
+ |
which has its own independent roughness expressions. |
| 690 |
+ |
Finally, the diffuse transmittance modifier is given as |
| 691 |
+ |
.I td_mod, |
| 692 |
+ |
which may also be "void" or "inherit". |
| 693 |
+ |
Note that any spectra or color for specular components must be |
| 694 |
+ |
carried by the named modifier(s). |
| 695 |
+ |
.PP |
| 696 |
+ |
The main advantage to this material over BRTDfunc and |
| 697 |
+ |
other programmable types described below is that the specular sampling is |
| 698 |
+ |
well-defined, so that all components are fully computed. |
| 699 |
+ |
.LP |
| 700 |
|
.UL Dielectric |
| 701 |
|
.PP |
| 702 |
|
A dielectric material is transparent, and it refracts light |
| 1265 |
|
0 |
| 1266 |
|
5+ nmA nmB s1 s2 .. sN |
| 1267 |
|
.DE |
| 1268 |
< |
The first two real arguments indicate the limits of the covered |
| 1268 |
> |
The first two real arguments indicate the extrema of the |
| 1269 |
|
spectral range in nanometers. |
| 1270 |
< |
Subsequent real values correspond to multipliers in each wavelength band, |
| 1271 |
< |
where the first band goes from nmA to nmA+(nmB-nmA)/N, and N is the |
| 1272 |
< |
number of bands (i.e., the number of real arguments minus 2). |
| 1273 |
< |
The nmA wavelength may be greater or less than the nmB wavelength, |
| 1216 |
< |
but they may not be equal, and their ordering must correspond to |
| 1217 |
< |
the ordering of the spectral values. |
| 1270 |
> |
Subsequent real values correspond to multipliers at each wavelength. |
| 1271 |
> |
The nmA wavelength may be greater or less than nmB, |
| 1272 |
> |
but they may not be equal, and their ordering matches |
| 1273 |
> |
the order of the spectral values. |
| 1274 |
|
A minimum of 3 values must be given, which would act |
| 1275 |
|
more or less the same as a constant RGB multiplier. |
| 1276 |
|
As with RGB values, spectral quantities normally range between 0 |
| 1307 |
|
pattern, similar to the colorfunc type. |
| 1308 |
|
.DS |
| 1309 |
|
mod specfunc id |
| 1310 |
< |
2+ sval funcfile transform |
| 1310 |
> |
2+ sfunc funcfile transform |
| 1311 |
|
0 |
| 1312 |
|
2+ nmA nmB A3 .. |
| 1313 |
|
.DE |
| 1314 |
|
Like the spectrum primitive, the wavelength range is specified |
| 1315 |
|
in the first two real arguments, and additional real values are |
| 1316 |
< |
accessible to the sval function. |
| 1316 |
> |
set in the evaluation context. |
| 1317 |
|
This function is fed a wavelenth sample |
| 1318 |
|
between nmA and nmB as its only argument, |
| 1319 |
|
and it returns the corresponding spectral intensity. |
| 1320 |
+ |
.LP |
| 1321 |
+ |
.UL Specdata |
| 1322 |
+ |
.PP |
| 1323 |
+ |
Specdata is like brightdata and colordata, but with more |
| 1324 |
+ |
than 3 specular samples. |
| 1325 |
+ |
.DS |
| 1326 |
+ |
mod specdata id |
| 1327 |
+ |
3+n+ |
| 1328 |
+ |
func datafile |
| 1329 |
+ |
funcfile x1 x2 .. xn transform |
| 1330 |
+ |
0 |
| 1331 |
+ |
m A1 A2 .. Am |
| 1332 |
+ |
.DE |
| 1333 |
+ |
The data file must have one more dimension than the coordinate |
| 1334 |
+ |
variable count, as this final dimension corresponds to the covered |
| 1335 |
+ |
spectrum. |
| 1336 |
+ |
The starting and ending wavelengths are specified in "datafile" |
| 1337 |
+ |
as well as the number of spectral samples. |
| 1338 |
+ |
The function "func" will be called with two parameters, the |
| 1339 |
+ |
interpolated spectral value for the current coordinate and the |
| 1340 |
+ |
associated wavelength. |
| 1341 |
+ |
If the spectrum is broken into 12 components, then 12 calls |
| 1342 |
+ |
will be made to "func" for the relevant ray evaluation. |
| 1343 |
+ |
.LP |
| 1344 |
+ |
.UL Specpict |
| 1345 |
+ |
.PP |
| 1346 |
+ |
Specpict is a special case of specdata, where the pattern is |
| 1347 |
+ |
a hyperspectral image stored in the common-exponent file format. |
| 1348 |
+ |
The dimensions of the image data are determined by the picture |
| 1349 |
+ |
just as with the colorpict primitive. |
| 1350 |
+ |
.DS |
| 1351 |
+ |
mod specpict id |
| 1352 |
+ |
5+ |
| 1353 |
+ |
func specfile |
| 1354 |
+ |
funcfile u v transform |
| 1355 |
+ |
0 |
| 1356 |
+ |
m A1 A2 .. Am |
| 1357 |
+ |
.DE |
| 1358 |
+ |
The function "func" is called with the interpolated pixel value |
| 1359 |
+ |
and the wavelength sample in nanometers, the same as specdata, |
| 1360 |
+ |
with as many calls made as there are components in "specfile". |
| 1361 |
|
.NH 3 |
| 1362 |
|
Mixtures |
| 1363 |
|
.PP |
