--- ray/doc/ray.html 2010/03/12 18:34:43 1.8 +++ ray/doc/ray.html 2014/07/31 18:32:41 1.19 @@ -1,7 +1,7 @@ -The RADIANCE 3.8 Synthetic Imaging System +The RADIANCE 4.2 Synthetic Imaging System @@ -9,7 +9,7 @@ The RADIANCE 3.8 Synthetic Imaging System

-The RADIANCE 3.8 Synthetic Imaging System +The RADIANCE 4.2 Synthetic Imaging System

@@ -1053,6 +1053,84 @@ unless the line integrals consider enclosed geometry.

+ + BSDF + + +
+ The BSDF material type loads an XML (eXtensible Markup Language) + file describing a bidirectional scattering distribution function. + Real arguments to this material may define additional + diffuse components that augment the BSDF data. + String arguments are used to define thickness for proxied + surfaces and the "up" orientation for the material. + +
+	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 sign of the thickness is important, as it indicates + whether the proxied geometry is behind the BSDF + surface (when thickness is positive) or in front (when + thickness is negative). +

+ 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.) 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. +

+ +

Antimatter @@ -1365,8 +1443,6 @@ A mixfunc mixes two modifiers procedurally. It i which serves as a form of opacity control when used with a material.) Vname is the coefficient defined in funcfile that determines the influence of foreground. The background coefficient is always (1-vname). - Since the references are not resolved until run-time, the last definitions of the modifier id's will be used. - This can result in modifier loops, which are detected by the renderer.

@@ -1528,10 +1604,8 @@ If no file is needed by a given primitive because all the required variables are global, a period (`.') can be given in place of the file name. It is also possible to give an expression instead -of a straight variable name in a scene file, -although such expressions should be kept -simple if possible. -Also, functions (requiring parameters) must be given +of a straight variable name in a scene file. +Functions (requiring parameters) must be given as names and not as expressions.

@@ -1714,16 +1788,10 @@ Pictures may be displayed directly under X11 using the or converted a standard image format using one of the following translators: