--- ray/doc/ray.1 2017/12/24 22:01:00 1.33 +++ ray/doc/ray.1 2018/06/26 14:42:18 1.35 @@ -1,4 +1,4 @@ -.\" RCSid "$Id: ray.1,v 1.33 2017/12/24 22:01:00 greg Exp $" +.\" RCSid "$Id: ray.1,v 1.35 2018/06/26 14:42:18 greg Exp $" .\" Print using the -ms macro package .DA 07/10/2016 .LP @@ -946,6 +946,30 @@ transmission or back-side reflection, only then the su invisible from behind. Unlike other data-driven material types, the BSDF type is fully supported and all parts of the distribution are properly sampled. +.LP +.UL aBSDF +.PP +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. +.DS +mod aBSDF id +5+ BSDFfile ux uy uz funcfile transform +0 +0|3|6|9 + rfdif gfdif bfdif + rbdif gbdif bbdif + rtdif gtdif btdif +.DE +.LP +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. .LP .UL Antimatter .PP