--- ray/doc/man/man1/mkpmap.1	2018/03/20 19:53:09	1.10
+++ ray/doc/man/man1/mkpmap.1	2018/12/06 20:13:13	1.11
@@ -1,5 +1,5 @@
-.\" RCSid "$Id: mkpmap.1,v 1.10 2018/03/20 19:53:09 rschregle Exp $"
-.TH MKPMAP 1 "$Date: 2018/03/20 19:53:09 $ $Revision: 1.10 $" RADIANCE
+.\" RCSid "$Id: mkpmap.1,v 1.11 2018/12/06 20:13:13 rschregle Exp $"
+.TH MKPMAP 1 "$Date: 2018/12/06 20:13:13 $ $Revision: 1.11 $" RADIANCE
 
 .SH NAME
 mkpmap - generate RADIANCE photon map
@@ -306,9 +306,12 @@ attempts before terminating with an error. This can be
 \fB\-apM\fR option.
 
 .SS Material Support
-The \fIplasfunc\fR, \fImetfunc\fR, \fItransfunc\fR, \fIbrtdfunc\fR,
-\fIplasdata\fR, \fImetdata\fR and \fItransdata\fR materials are not
-supported by the photon mapping extension. Use the newer \fIbsdf\fR material
+Not all materials are fully supported by the photon map extension.  The
+\fIplasfunc\fR, \fImetfunc\fR, \fItransfunc\fR, \fIplasdata\fR,
+\fImetdata\fR and \fItransdata\fR materials currently only scatter photons
+diffusely, and will not produce caustics.  The \fIbrtdfunc\fR material only
+produces caustics via ideal (mirror) specular reflection and transmission. 
+For more realistic scattering behaviour, use the newer \fIbsdf\fR material
 instead.
 .PP
 Virtual light sources (normally enabled with the \fImirror\fR material) are