| 834 |
|
<p> |
| 835 |
|
|
| 836 |
|
<dt> |
| 837 |
+ |
<a NAME="WGMDfunc"> |
| 838 |
+ |
<b>WGMDfunc</b> |
| 839 |
+ |
</a> |
| 840 |
+ |
|
| 841 |
+ |
<dd> |
| 842 |
+ |
WGMDfunc is a more programmable version of <a HREF="#Trans2">trans2</a>, |
| 843 |
+ |
with separate modifier paths and variables to control each component. |
| 844 |
+ |
(WGMD stands for Ward-Geisler-Moroder-Duer, which is the basis for |
| 845 |
+ |
this empirical model, similar to previous ones beside Ashik2.) |
| 846 |
+ |
The specification of this material is given below. |
| 847 |
+ |
<pre> |
| 848 |
+ |
mod WGMDfunc id |
| 849 |
+ |
13+ rs_mod rs rs_urough rs_vrough |
| 850 |
+ |
ts_mod ts ts_urough ts_vrough |
| 851 |
+ |
td_mod |
| 852 |
+ |
ux uy uz funcfile transform |
| 853 |
+ |
0 |
| 854 |
+ |
9+ rfdif gfdif bfdif |
| 855 |
+ |
rbdif gbdif bbdif |
| 856 |
+ |
rtdif gtdif btdif |
| 857 |
+ |
A10 .. |
| 858 |
+ |
</pre> |
| 859 |
+ |
|
| 860 |
+ |
The sum of specular reflectance (<I>rs</I>), specular transmittance (<I>ts</I>), |
| 861 |
+ |
diffuse reflectance (<I>rfdif gfdif bfdif</I> for front and <I>rbdif gbdif bbdif</I> for back) |
| 862 |
+ |
and diffuse transmittance (<I>rtdif gtdif btdif</I>) should be less than 1 for each |
| 863 |
+ |
channel. |
| 864 |
+ |
|
| 865 |
+ |
<p> |
| 866 |
+ |
|
| 867 |
+ |
Unique to this material, separate modifier channels are |
| 868 |
+ |
provided for each component. |
| 869 |
+ |
The main modifier is used on the diffuse reflectance, both |
| 870 |
+ |
front and back. |
| 871 |
+ |
The <I>rs_mod</I> modifier is used for specular reflectance. |
| 872 |
+ |
If "void" is given for <I>rs_mod</I>, |
| 873 |
+ |
then the specular reflection color will be white. |
| 874 |
+ |
The special "inherit" keyword may also be given, in which case |
| 875 |
+ |
specular reflectance will share the main modifier. |
| 876 |
+ |
This behavior is replicated for the specular transmittance modifier |
| 877 |
+ |
<I>ts_mod</I>, which also has its own independent roughness expressions. |
| 878 |
+ |
Finally, the diffuse transmittance modifier is given as |
| 879 |
+ |
<I>td_mod</I>, which may also be "void" or "inherit". |
| 880 |
+ |
Note that any spectra or color for specular components must be |
| 881 |
+ |
carried by the named modifier(s). |
| 882 |
+ |
|
| 883 |
+ |
<p> |
| 884 |
+ |
|
| 885 |
+ |
The main advantage to this material over |
| 886 |
+ |
<a HREF="#BRTDfunc">BRTDfunc</a> and |
| 887 |
+ |
other programmable types described below is that the specular sampling is |
| 888 |
+ |
well-defined, so that all components are fully computed. |
| 889 |
+ |
|
| 890 |
+ |
<p> |
| 891 |
+ |
|
| 892 |
+ |
<dt> |
| 893 |
|
<a NAME="Dielectric"> |
| 894 |
|
<b>Dielectric</b> |
| 895 |
|
</a> |
| 1538 |
|
</pre> |
| 1539 |
|
|
| 1540 |
|
<p> |
| 1541 |
< |
The first two real arguments indicate the limits of the covered |
| 1541 |
> |
The first two real arguments indicate the extrema of the |
| 1542 |
|
spectral range in nanometers. |
| 1543 |
< |
Subsequent real values correspond to multipliers in each wavelength band, |
| 1488 |
< |
where the first band goes from nmA to nmA+(nmB-nmA)/N, and N is the |
| 1489 |
< |
number of bands (i.e., the number of real arguments minus 2). |
| 1543 |
> |
Subsequent real values correspond to multipliers at each wavelength. |
| 1544 |
|
The nmA wavelength may be greater or less than nmB, |
| 1545 |
|
but they may not be equal, and their ordering matches |
| 1546 |
|
the order of the spectral values. |
| 1596 |
|
|
| 1597 |
|
<pre> |
| 1598 |
|
mod specfunc id |
| 1599 |
< |
2+ sval funcfile transform |
| 1599 |
> |
2+ sfunc funcfile transform |
| 1600 |
|
0 |
| 1601 |
|
2+ nmA nmB A3 .. |
| 1602 |
|
</pre> |
| 1604 |
|
<p> |
| 1605 |
|
Like the spectrum primitive, the wavelength range is specified |
| 1606 |
|
in the first two real arguments, and additional real values are |
| 1607 |
< |
accessible to the sval function. |
| 1607 |
> |
set in the evaluation context. |
| 1608 |
|
This function is fed a wavelenth sample |
| 1609 |
|
between nmA and nmB as its only argument, |
| 1610 |
|
and it returns the corresponding spectral intensity. |
| 1611 |
+ |
|
| 1612 |
+ |
<dt> |
| 1613 |
+ |
<a NAME="Specdata"> |
| 1614 |
+ |
<b>Specdata</b> |
| 1615 |
+ |
</a> |
| 1616 |
+ |
|
| 1617 |
+ |
<dd> |
| 1618 |
+ |
Specdata is like brightdata and colordata, but with more |
| 1619 |
+ |
than 3 specular samples. |
| 1620 |
+ |
|
| 1621 |
+ |
<pre> |
| 1622 |
+ |
mod specdata id |
| 1623 |
+ |
3+n+ |
| 1624 |
+ |
func datafile |
| 1625 |
+ |
funcfile x1 x2 .. xn transform |
| 1626 |
+ |
0 |
| 1627 |
+ |
m A1 A2 .. Am |
| 1628 |
+ |
</pre> |
| 1629 |
+ |
|
| 1630 |
+ |
<p> |
| 1631 |
+ |
The data file must have one more dimension than the coordinate |
| 1632 |
+ |
variable count, as this final dimension corresponds to the covered |
| 1633 |
+ |
spectrum. |
| 1634 |
+ |
The starting and ending wavelengths are specified in "datafile" |
| 1635 |
+ |
as well as the number of spectral samples. |
| 1636 |
+ |
The function "func" will be called with two parameters, the |
| 1637 |
+ |
interpolated spectral value for the current coordinate and the |
| 1638 |
+ |
associated wavelength. |
| 1639 |
+ |
If the spectrum is broken into 12 components, then 12 calls |
| 1640 |
+ |
will be made to "func" for the relevant ray evaluation. |
| 1641 |
+ |
|
| 1642 |
+ |
<dt> |
| 1643 |
+ |
<a NAME="Specpict"> |
| 1644 |
+ |
<b>Specpict</b> |
| 1645 |
+ |
</a> |
| 1646 |
+ |
|
| 1647 |
+ |
<dd> |
| 1648 |
+ |
Specpict is a special case of specdata, where the pattern is |
| 1649 |
+ |
a hyperspectral image stored in the common-exponent file format. |
| 1650 |
+ |
The dimensions of the image data are determined by the picture |
| 1651 |
+ |
just as with the colorpict primitive. |
| 1652 |
+ |
|
| 1653 |
+ |
<pre> |
| 1654 |
+ |
mod specpict id |
| 1655 |
+ |
5+ |
| 1656 |
+ |
func specfile |
| 1657 |
+ |
funcfile u v transform |
| 1658 |
+ |
0 |
| 1659 |
+ |
m A1 A2 .. Am |
| 1660 |
+ |
</pre> |
| 1661 |
+ |
|
| 1662 |
+ |
<p> |
| 1663 |
+ |
The function "func" is called with the interpolated pixel value |
| 1664 |
+ |
and the wavelength sample in nanometers, the same as specdata, |
| 1665 |
+ |
with as many calls made as there are components in "specfile". |
| 1666 |
|
|
| 1667 |
|
</dl> |
| 1668 |
|
|
