--- ray/doc/ray.html 2014/07/31 18:32:41 1.19 +++ ray/doc/ray.html 2024/12/09 19:21:38 1.39 @@ -1,7 +1,8 @@ + -The RADIANCE 4.2 Synthetic Imaging System +The RADIANCE 6.0 Synthetic Imaging System @@ -9,7 +10,7 @@ The RADIANCE 4.2 Synthetic Imaging System

-The RADIANCE 4.2 Synthetic Imaging System +The RADIANCE 6.0 Synthetic Imaging System

@@ -82,7 +83,7 @@ The diagram in Figure 1 shows the flow between program (ovals). The central program is rpict, which produces a picture from a scene description. -Rview is a variation of rpict that computes and displays images +Rvu is a variation of rpict that computes and displays images interactively, and rtrace computes single ray values. Other programs (not shown) connect many of these elements together, such as the executive programs @@ -797,7 +798,8 @@ unless the line integrals consider enclosed geometry.

Trans2 is the anisotropic version of trans. - The string arguments are the same as for plastic2, and the real arguments are the same as for trans but with an additional roughness value. + The string arguments are the same as for plastic2, + and the real arguments are the same as for trans but with an additional roughness value. 
         mod trans2 id
@@ -809,6 +811,85 @@ unless the line integrals consider enclosed geometry.
 

 
 

+	
+	Ashik2
+	
+
+

+	Ashik2 is the anisotropic reflectance model by Ashikhmin & Shirley.
+	The string arguments are the same as for plastic2, but the real
+	arguments have additional flexibility to specify the specular color.
+	Also, rather than roughness, specular power is used, which has no
+	physical meaning other than larger numbers are equivalent to a smoother
+	surface.
+	Unlike other material types, total reflectance is the sum of
+	diffuse and specular colors, and should be adjusted accordingly.
+
+	mod ashik2 id
+	4+ ux uy uz funcfile transform
+	0
+	8 dred dgrn dblu sred sgrn sblu u-power v-power
+

+
+

+
+

+	
+	WGMDfunc
+	
+
+

+	WGMDfunc is a more programmable version of trans2,
+	with separate modifier paths and variables to control each component.
+	(WGMD stands for Ward-Geisler-Moroder-Duer, which is the basis for
+	this empirical model, similar to previous ones beside Ashik2.)
+	The specification of this material is given below.
+
+	mod WGMDfunc id
+	13+ rs_mod  rs  rs_urough rs_vrough
+	    ts_mod  ts  ts_urough ts_vrough
+	    td_mod
+	    ux uy uz  funcfile  transform
+	0
+	9+  rfdif gfdif bfdif
+	    rbdif gbdif bbdif
+	    rtdif gtdif btdif
+	    A10 ..
+

+
+The sum of specular reflectance (rs), specular transmittance (ts),
+diffuse reflectance (rfdif gfdif bfdif for front and rbdif gbdif bbdif for back)
+and diffuse transmittance (rtdif gtdif btdif) should be less than 1 for each
+channel.
+
+

+
+Unique to this material, separate modifier channels are
+provided for each component.
+The main modifier is used on the diffuse reflectance, both
+front and back.
+The rs_mod modifier is used for specular reflectance.
+If "void" is given for rs_mod,
+then the specular reflection color will be white.
+The special "inherit" keyword may also be given, in which case
+specular reflectance will share the main modifier.
+This behavior is replicated for the specular transmittance modifier
+ts_mod, which also has its own independent roughness expressions.
+Finally, the diffuse transmittance modifier is given as
+td_mod, which may also be "void" or "inherit".
+Note that any spectra or color for specular components must be
+carried by the named modifier(s).
+
+

+
+The main advantage to this material over
+BRTDfunc and
+other programmable types described below is that the specular sampling is
+well-defined, so that all components are fully computed.
+
+

+
+

 	
 	Dielectric
 	
@@ -1131,6 +1212,38 @@ unless the line integrals consider enclosed geometry.
 

 
 

+	
+	aBSDF
+	
+
+

+	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.
+
+
+	mod aBSDF id
+	5+ BSDFfile ux uy uz funcfile transform
+	0
+	0|3|6|9
+	     rfdif gfdif bfdif
+	     rbdif gbdif bbdif
+	     rtdif gtdif btdif
+

+
+

+	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.
+

+
+

 	
 	Antimatter
 	
@@ -1404,6 +1517,153 @@ or:
 	A section of text meant to  depict  a  picture, perhaps using a special purpose font such as hexbit4x1.fnt, calls for uniform  spacing.   
 	Reasonable  magnitudes  for  proportional  spacing are between 0.1 (for tightly spaced characters) and 0.3 (for wide spacing).
 
+

+
+

+	
+	Spectrum
+	
+
+

+	The spectrum primitive is the most basic type for introducing spectral
+	color to a material.
+	Since materials only provide RGB parameters, spectral patterns
+	are the only way to superimpose wavelength-dependent behavior.
+
+
+        mod spectrum id
+	0
+	0
+	5+ nmA nmB s1 s2 .. sN
+

+
+

+	The first two real arguments indicate the extrema of the
+	spectral range in nanometers.
+	Subsequent real values correspond to multipliers at each wavelength.
+	The nmA wavelength may be greater or less than nmB,
+	but they may not be equal, and their ordering matches
+	the order of the spectral values.
+	A minimum of 3 values must be given, which would act
+	more or less the same as a constant RGB multiplier.
+	As with RGB values, spectral quantities normally range between 0
+	and 1 at each wavelength, or average to 1.0 against a standard
+	sensitivity functions such as V(lambda).
+	The best results obtain when the spectral range and number
+	of samples match rendering options, though resampling will handle
+	any differences, zero-filling wavelenths outside the nmA to nmB
+	range.
+	A warning will be issued if the given wavelength range does not
+	adequately cover the visible spectrum.
+
+

+
+

+	
+	Specfile
+	
+
+

+	The specfile primitive is equivalent to the spectrum type, but
+	the wavelength range and values are contained in a 1-dimensional
+	data file.
+	This may be a more convenient way to specify a spectral color,
+	especially one corresponding to a standard illuminant such as D65
+	or a library of measured spectra.
+
+
+        mod specfile id
+	1 datafile
+	0
+	0
+

+
+

+	As with the spectrum type, rendering wavelengths outside the defined
+	range will be zero-filled.
+	Unlike the spectrum type, the file may contain non-uniform samples.
+
+

+
+

+	
+	Specfunc
+	
+
+

+	The specfunc primitive offers dynamic control over a spectral
+	pattern, similar to the colorfunc type.
+
+
+        mod specfunc id
+	2+ sfunc funcfile transform
+	0
+	2+ nmA nmB A3 ..
+

+
+

+	Like the spectrum primitive, the wavelength range is specified
+	in the first two real arguments, and additional real values are
+	set in the evaluation context.
+	This function is fed a wavelenth sample
+	between nmA and nmB as its only argument,
+	and it returns the corresponding spectral intensity.
+
+

+       
+       Specdata
+       
+
+

+	Specdata is like brightdata and colordata, but with more
+	than 3 specular samples.
+
+
+	mod specdata id
+	3+n+
+		func datafile
+		funcfile x1 x2 .. xn transform
+	0
+	m A1 A2 .. Am
+

+
+

+	The data file must have one more dimension than the coordinate
+	variable count, as this final dimension corresponds to the covered
+	spectrum.
+	The starting and ending wavelengths are specified in "datafile"
+	as well as the number of spectral samples.
+	The function "func" will be called with two parameters, the
+	interpolated spectral value for the current coordinate and the
+	associated wavelength.
+	If the spectrum is broken into 12 components, then 12 calls
+	will be made to "func" for the relevant ray evaluation.
+
+

+       
+       Specpict
+       
+
+

+	Specpict is a special case of specdata, where the pattern is
+	a hyperspectral image stored in the common-exponent file format.
+	The dimensions of the image data are determined by the picture
+	just as with the colorpict primitive.
+
+
+	mod specpict id
+	5+
+		func specfile
+		funcfile u v transform
+	0
+	m A1 A2 .. Am
+

+
+

+	The function "func" is called with the interpolated pixel value
+	and the wavelength sample in nanometers, the same as specdata,
+	with as many calls made as there are components in "specfile".
+
 
 
 

@@ -1414,6 +1674,7 @@ or:
 
 
 A mixture is a blend of one or more materials or textures and patterns.
+Blended materials should not be light source types or virtual source types.
 The basic types are given below.
 
 

@@ -1486,7 +1747,6 @@ A mixfunc mixes  two  modifiers  procedurally.   It  i
 	arguments, the red, green and blue values
 	corresponding to the pixel at (u,v).
 
-
 

 
 

@@ -1752,7 +2012,7 @@ The details of this process  are  not  important, but 
 directs the use of a scene description.