--- ray/doc/ray.html 2005/07/24 21:05:08 1.5 +++ ray/doc/ray.html 2011/07/15 17:45:46 1.15 @@ -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

@@ -564,7 +564,7 @@ A material defines the way light interacts with a sur

- Mirror is used for planar surfaces that produce secondary source reflections. + Mirror is used for planar surfaces that produce virtual source reflections. This material should be used sparingly, as it may cause the light source calculation to blow up if it is applied to many small surfaces. This material is only supported for flat surfaces such as polygons and rings. The arguments are simply the RGB reflectance values, which should be between 0 and 1. @@ -587,12 +587,12 @@ This is only appropriate if the surface hides other (m
- The prism1 material is for general light redirection from prismatic glazings, generating secondary light sources. + The prism1 material is for general light redirection from prismatic glazings, generating virtual light sources. It can only be used to modify a planar surface (i.e., a polygon or disk) and should not result in either light concentration or scattering. The new direction of the ray can be on either side of the material, - and the definitions must have the correct bidirectional properties to work properly with secondary light sources. + and the definitions must have the correct bidirectional properties to work properly with virtual light sources. The arguments give the coefficient for the redirected light and its direction. 
@@ -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 +1053,84 @@ 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.
 
 

@@ -1749,7 +1823,7 @@ 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
@@ -1783,7 +1857,7 @@ are met:
       nor may "Radiance" appear in their name, without prior written
       permission of Lawrence Berkeley National Laboratory.
 
-THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
+THIS SOFTWARE IS PROVIDED ``AS IS" AND ANY EXPRESSED OR IMPLIED
 WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 DISCLAIMED.   IN NO EVENT SHALL Lawrence Berkeley National Laboratory OR
@@ -1822,20 +1896,30 @@ Ecole  Polytechnique  Federale de Lausanne (EPFL Unive
 
 

 

@@ -1920,6 +2004,7 @@ SURFACES	MATERIALS	TEXTURES	PATTERNS	MIXTURES
 		Plasdata
 		Metdata
 		Transdata
+		BSDF
 		Antimatter