docs: Added description of new WGMDfunc material

LBNL-ETA · Dec 9, 2024 · 1e5553a · 1e5553a
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diff --git a/doc/ray.1 b/doc/ray.1
@@ -1,8 +1,8 @@
-.\" RCSid "$Id: ray.1,v 1.46 2023/12/13 23:26:16 greg Exp $"
+.\" RCSid "$Id: ray.1,v 1.47 2024/12/09 19:21:38 greg Exp $"
 .\" Print using the -ms macro package
-.DA 11/13/2023
+.DA 12/09/2024
 .LP
-.tl """Copyright \(co 2023 Regents, University of California
+.tl """Copyright \(co 2024 Regents, University of California
 .sp 2
 .TL
 The
@@ -639,6 +639,64 @@ mod ashik2 id
 8 dred dgrn dblu sred sgrn sblu u-power v-power
 .DE
 .LP
+.UL WGMDfunc
+.PP
+WGMDfunc is a more programmable version of trans2,
+with separate modifier paths and variables to control each component.
+(WGMD stands for Ward-Geisler-Moroder-Duer, which is the basis for
+this empirical model, similar to the previous ones beside Ashik2.)\0
+The specification of this material is given below.
+.DS
+mod WGMDfunc id
+13+ rs_mod  rs  rs_urough rs_vrough
+    ts_mod  ts  ts_urough ts_vrough
+    td_mod
+    ux uy uz  funcfile  transform
+0
+9+  rfdif gfdif bfdif
+    rbdif gbdif bbdif
+    rtdif gtdif btdif
+    A10 ..
+.DE
+The sum of specular reflectance (
+.I rs
+), specular transmittance (
+.I ts
+), diffuse reflectance (
+.I "rfdif gfdif bfdif"
+for front and
+.I "rbdif gbdif bbdif"
+for back)
+and diffuse transmittance (
+.I "rtdif gtdif btdif"
+) should be less than 1 for each
+channel.
+.PP
+Unique to this material, separate modifier channels are
+provided for each component.
+The main modifier is used on the diffuse reflectance, both
+front and back.
+The
+.I rs_mod
+modifier is used for specular reflectance.
+If "void" is given for
+.I rs_mod,
+then the specular reflection color will be white.
+The special "inherit" keyword may also be given, in which case
+specular reflectance will share the main modifier.
+This behavior is replicated for the specular transmittance modifier
+.I ts_mod,
+which has its own independent roughness expressions.
+Finally, the diffuse transmittance modifier is given as
+.I td_mod,
+which may also be "void" or "inherit".
+Note that any spectra or color for specular components must be
+carried by the named modifier(s).
+.PP
+The main advantage to this material over BRTDfunc and
+other programmable types described below is that the specular sampling is
+well-defined, so that all components are fully computed.
+.LP
 .UL Dielectric
 .PP
 A dielectric material is transparent, and it refracts light

diff --git a/doc/ray.html b/doc/ray.html
@@ -1,5 +1,5 @@
 <html>
-<!-- RCSid $Id: ray.html,v 1.38 2023/12/13 23:26:16 greg Exp $ -->
+<!-- RCSid $Id: ray.html,v 1.39 2024/12/09 19:21:38 greg Exp $ -->
 <head>
 <title>
 The RADIANCE 6.0 Synthetic Imaging System
@@ -833,6 +833,62 @@ <h4>
 
 <p>
 
+<dt>
+	<a NAME="WGMDfunc">
+	<b>WGMDfunc</b>
+	</a>
+
+<dd>
+	WGMDfunc is a more programmable version of <a HREF="#Trans2">trans2</a>,
+	with separate modifier paths and variables to control each component.
+	(WGMD stands for Ward-Geisler-Moroder-Duer, which is the basis for
+	this empirical model, similar to previous ones beside Ashik2.)
+	The specification of this material is given below.
+<pre>
+	mod WGMDfunc id
+	13+ rs_mod  rs  rs_urough rs_vrough
+	    ts_mod  ts  ts_urough ts_vrough
+	    td_mod
+	    ux uy uz  funcfile  transform
+	0
+	9+  rfdif gfdif bfdif
+	    rbdif gbdif bbdif
+	    rtdif gtdif btdif
+	    A10 ..
+</pre>
+
+The sum of specular reflectance (<I>rs</I>), specular transmittance (<I>ts</I>),
+diffuse reflectance (<I>rfdif gfdif bfdif</I> for front and <I>rbdif gbdif bbdif</I> for back)
+and diffuse transmittance (<I>rtdif gtdif btdif</I>) should be less than 1 for each
+channel.
+
+<p>
+
+Unique to this material, separate modifier channels are
+provided for each component.
+The main modifier is used on the diffuse reflectance, both
+front and back.
+The <I>rs_mod</I> modifier is used for specular reflectance.
+If "void" is given for <I>rs_mod</I>,
+then the specular reflection color will be white.
+The special "inherit" keyword may also be given, in which case
+specular reflectance will share the main modifier.
+This behavior is replicated for the specular transmittance modifier
+<I>ts_mod</I>, which also has its own independent roughness expressions.
+Finally, the diffuse transmittance modifier is given as
+<I>td_mod</I>, which may also be "void" or "inherit".
+Note that any spectra or color for specular components must be
+carried by the named modifier(s).
+
+<p>
+
+The main advantage to this material over
+<a HREF="#BRTDfunc">BRTDfunc</a> and
+other programmable types described below is that the specular sampling is
+well-defined, so that all components are fully computed.
+
+<p>
+
 <dt>
 	<a NAME="Dielectric">
 	<b>Dielectric</b>