--- ray/doc/ray.html 2006/05/10 19:50:30 1.6 +++ ray/doc/ray.html 2011/04/06 22:00:46 1.10 @@ -1,7 +1,7 @@ -The RADIANCE 3.7 Synthetic Imaging System +The RADIANCE 4.1 Synthetic Imaging System @@ -9,7 +9,7 @@ The RADIANCE 3.7 Synthetic Imaging System

-The RADIANCE 3.7 Synthetic Imaging System +The RADIANCE 4.1 Synthetic Imaging System

@@ -659,7 +659,7 @@ a perfectly scattering medium (no absorption). The scattering eccentricity parameter will likewise override the global setting if it is present. Scattering eccentricity indicates how much scattered light favors the -forward direction, as fit by the Heyney-Greenstein function: +forward direction, as fit by the Henyey-Greenstein function: 

 	P(theta) = (1 - g*g) / (1 + g*g - 2*g*cos(theta))^1.5
@@ -1053,6 +1053,78 @@ 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 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.
+

+
+

 	
 	Antimatter
 	
@@ -1365,8 +1437,6 @@ 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 +1598,8 @@ 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.
 
 

@@ -1749,7 +1817,7 @@ or converted a standard image format using one of the 
 
 The Radiance Software License, Version 1.0
 
-Copyright (c) 1990 - 2002 The Regents of the University of California,
+Copyright (c) 1990 - 2010 The Regents of the University of California,
 through Lawrence Berkeley National Laboratory.   All rights reserved.
 
 Redistribution and use in source and binary forms, with or without
@@ -1822,19 +1890,24 @@ Ecole  Polytechnique  Federale de Lausanne (EPFL Unive