@@ -1053,6 +1053,78 @@ unless the line integrals consider enclosed geometry.
+ mod BSDF id + 6+ thick BSDFfile ux uy uz funcfile transform + 0 + 0|3|6|9 + rfdif gfdif bfdif + rbdif gbdif bbdif + rtdif gtdif btdif ++ +
+ The first string argument is a "thickness" parameter that may be used + to hide detail geometry being proxied by an aggregate BSDF material. + If a view or shadow ray hits a BSDF proxy with non-zero thickness, + it will pass directly through as if the surface were not there. + Similar to the illum type, this permits direct viewing and + shadow testing of complex geometry. + The BSDF is used when a scattered (indirect) ray hits the surface, + and any transmitted sample rays will be offset by the thickness amount + to avoid the hidden geometry and gather samples from the other side. + In this manner, BSDF surfaces can improve the results for indirect + scattering from complex systems without sacrificing appearance or + shadow accuracy. + If the BSDF has transmission and back-side reflection data, + a parallel BSDF surface may be + placed slightly less than the given thickness away from the front surface + to enclose the complex geometry on both sides. +
+ The second string argument is the name of the BSDF file, which is + found in the usual auxiliary locations. + The following three string parameters name variables for an "up" vector, + which together with the surface normal, define the + local coordinate system that orients the BSDF. + These variables, along with the thickness, are defined in a function + file given as the next string argument. + An optional transform is used to scale the thickness and reorient the up vector. +
+ If no real arguments are given, the BSDF is used by itself to determine + reflection and transmission. + If there are at least 3 real arguments, the first triplet is an + additional diffuse reflectance for the front side. + At least 6 real arguments adds diffuse reflectance to the rear side of the surface. + If there are 9 real arguments, the final triplet will be taken as an additional + diffuse transmittance. + All diffuse components as well as the non-diffuse transmission are + modified by patterns applied to this material. + The non-diffuse reflection from either side are unaffected. + Textures perturb the effective surface normal in the usual way. +
+ The surface normal of this type is not altered to face the incoming ray, + so the front and back BSDF reflections may differ. + (Transmission is identical front-to-back by physical law.)\0 + If back visibility is turned off during rendering and there is no + transmission or back-side reflection, only then 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. +
+ +