--- ray/doc/ray.1	2023/12/13 23:26:16	1.46
+++ ray/doc/ray.1	2025/05/29 16:42:28	1.48
@@ -1,8 +1,8 @@
-.\" RCSid "$Id: ray.1,v 1.46 2023/12/13 23:26:16 greg Exp $"
+.\" RCSid "$Id: ray.1,v 1.48 2025/05/29 16:42:28 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
@@ -422,6 +422,23 @@ mod mirror id
 0
 3 red green blue
 .DE
+While alternate materials that are reflective will appear as normal,
+indirect rays will use the mirror's reflectance rather than the
+alternate type.
+Transmitting materials are an exception, where both transmission and
+reflection will use the alternate type for all rays not specifically
+targeting virtual light sources.
+Therefore, transmitting alternate types should only have pure specular
+reflection if they reflect at all, to maintain a valid calculation.
+.PP
+The mirror material type reflects light sources only from the front side
+of a surface, regardless of any alternate material.
+If virtual source generation is desired on both sides, two coincident
+surfaces with opposite normal orientations may be employed to achieve
+this effect.
+The reflectance and alternate material type may be 
+different for the overlapped surfaces,
+and the two sides will behave accordingly.
 .LP
 .UL Prism1
 .PP
@@ -638,6 +655,64 @@ mod ashik2 id
 0
 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