--- ray/doc/ray.html 2017/08/26 16:07:22 1.24
+++ ray/doc/ray.html 2018/06/26 14:42:18 1.26
@@ -1,5 +1,5 @@
-
+
The RADIANCE 5.2 Synthetic Imaging System
@@ -1151,6 +1151,38 @@ unless the line integrals consider enclosed geometry.
the surface will be invisible from behind. Unlike other
data-driven material types, the BSDF type is fully supported
and all parts of the distribution are properly sampled.
+<p>
+
+<dt>
+ <a NAME="aBSDF">
+ <b>aBSDF</b>
+ </a>
+
+<dd>
+ The aBSDF material is identical to the BSDF type with two
+ important differences. First, proxy geometry is not
+ supported, so there is no thickness parameter. Second, an
+ aBSDF is assumed to have some specular through component
+ (the ’a’ stands for "aperture"),
+ which is treated specially during the direct calculation
+ and when viewing the material. Based on the BSDF data, the
+ coefficient of specular transmission is determined and used
+ for modifying unscattered shadow and view rays.
+
+<pre>
+ mod aBSDF id
+ 5+ BSDFfile ux uy uz funcfile transform
+ 0
+ 0|3|6|9
+ rfdif gfdif bfdif
+ rbdif gbdif bbdif
+ rtdif gtdif btdif
+</pre>
+
+<p>
+ If a material has no specular transmitted component, it is
+ much better to use the BSDF type with a zero thickness
+ than to use aBSDF.
<p>
<dt>