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Revision 1.9 by greg, Wed May 10 19:50:30 2006 UTC vs.
Revision 1.30 by greg, Sun Jul 10 23:41:37 2016 UTC

# Line 1 | Line 1
1 < .\" RCSid "$Id"
1 > .\" RCSid "$Id$"
2   .\" Print using the -ms macro package
3 < .DA 1/20/99
3 > .DA 07/10/2016
4   .LP
5 < .tl """Copyright \(co 2003 Regents, University of California
5 > .tl """Copyright \(co 2016 Regents, University of California
6   .sp 2
7   .TL
8   The
# Line 491 | Line 491 | a perfectly scattering medium (no absorption).
491   The scattering eccentricity parameter will likewise override the global
492   setting if it is present.
493   Scattering eccentricity indicates how much scattered light favors the
494 < forward direction, as fit by the Heyney-Greenstein function:
494 > forward direction, as fit by the Henyey-Greenstein function:
495   .DS
496   P(theta) = (1 - g*g) / (1 + g*g - 2*g*cos(theta))^1.5
497   .DE
# Line 622 | Line 622 | mod trans2 id
622   8 red green blue spec urough vrough trans tspec
623   .DE
624   .LP
625 + .UL Ashik2
626 + .PP
627 + Ashik2 is the anisotropic reflectance model by Ashikhmin & Shirley.
628 + The string arguments are the same as for plastic2, but the real
629 + arguments have additional flexibility to specify the specular color.
630 + Also, rather than roughness, specular power is used, which has no
631 + physical meaning other than larger numbers are equivalent to a smoother
632 + surface.
633 + .DS
634 + mod ashik2 id
635 + 4+ ux uy uz funcfile transform
636 + 0
637 + 8 dred dgrn dblu sred sgrn sblu u-power v-power
638 + .DE
639 + .LP
640   .UL Dielectric
641   .PP
642   A dielectric material is transparent, and it refracts light
# Line 865 | Line 880 | mod transdata id
880   6+ red green blue rspec trans tspec A7 ..
881   .DE
882   .LP
883 + .UL BSDF
884 + .PP
885 + The BSDF material type loads an XML (eXtensible Markup Language)
886 + file describing a bidirectional scattering distribution function.
887 + Real arguments to this material may define additional
888 + diffuse components that augment the BSDF data.
889 + String arguments are used to define thickness for proxied
890 + surfaces and the "up" orientation for the material.
891 + .DS
892 + mod BSDF id
893 + 6+ thick BSDFfile ux uy uz funcfile transform
894 + 0
895 + 0|3|6|9
896 +     rfdif gfdif bfdif
897 +     rbdif gbdif bbdif
898 +     rtdif gtdif btdif
899 + .DE
900 + The first string argument is a "thickness" parameter that may be used
901 + to hide detail geometry being proxied by an aggregate BSDF material.
902 + If a view or shadow ray hits a BSDF proxy with non-zero thickness,
903 + it will pass directly through as if the surface were not there.
904 + Similar to the illum type, this permits direct viewing and
905 + shadow testing of complex geometry.
906 + The BSDF is used when a scattered (indirect) ray hits the surface,
907 + and any transmitted sample rays will be offset by the thickness amount
908 + to avoid the hidden geometry and gather samples from the other side.
909 + In this manner, BSDF surfaces can improve the results for indirect
910 + scattering from complex systems without sacrificing appearance or
911 + shadow accuracy.
912 + If the BSDF has transmission and back-side reflection data,
913 + a parallel BSDF surface may be
914 + placed slightly less than the given thickness away from the front surface
915 + to enclose the complex geometry on both sides.
916 + The sign of the thickness is important, as it indicates whether the
917 + proxied geometry is behind the BSDF surface (when thickness is positive)
918 + or in front (when thickness is negative).
919 + .LP
920 + The second string argument is the name of the BSDF file, which is
921 + found in the usual auxiliary locations.
922 + The following three string parameters name variables for an "up" vector,
923 + which together with the surface normal, define the
924 + local coordinate system that orients the BSDF.
925 + These variables, along with the thickness, are defined in a function
926 + file given as the next string argument.
927 + An optional transform is used to scale the thickness and reorient the up vector.
928 + .LP
929 + If no real arguments are given, the BSDF is used by itself to determine
930 + reflection and transmission.
931 + If there are at least 3 real arguments, the first triplet is an
932 + additional diffuse reflectance for the front side.
933 + At least 6 real arguments adds diffuse reflectance to the rear side of the surface.
934 + If there are 9 real arguments, the final triplet will be taken as an additional
935 + diffuse transmittance.
936 + All diffuse components as well as the non-diffuse transmission are
937 + modified by patterns applied to this material.
938 + The non-diffuse reflection from either side are unaffected.
939 + Textures perturb the effective surface normal in the usual way.
940 + .LP
941 + The surface normal of this type is not altered to face the incoming ray,
942 + so the front and back BSDF reflections may differ.
943 + (Transmission is identical front-to-back by physical law.)\0
944 + If back visibility is turned off during rendering and there is no
945 + transmission or back-side reflection, only then the surface will be
946 + invisible from behind.
947 + Unlike other data-driven material types, the BSDF type is fully
948 + supported and all parts of the distribution are properly sampled.
949 + .LP
950   .UL Antimatter
951   .PP
952   Antimatter is a material that can "subtract" volumes from other volumes.
# Line 1088 | Line 1170 | between 0.1 (for tightly spaced characters) and 0.3 (f
1170   Mixtures
1171   .PP
1172   A mixture is a blend of one or more materials or textures and patterns.
1173 + Blended materials should not be light source types or virtual source types.
1174   The basic types are given below.
1175   .LP
1176   .UL Mixfunc
# Line 1109 | Line 1192 | which serves as a form of opacity control when used wi
1192   Vname is the coefficient defined in funcfile that determines the influence
1193   of foreground.
1194   The background coefficient is always (1-vname).
1112 – Since the references are not resolved until runtime, the last
1113 – definitions of the modifier id's will be used.
1114 – This can result in modifier loops, which are detected by the
1115 – renderer.
1195   .LP
1196   .UL Mixdata
1197   .PP
# Line 1239 | Line 1318 | If no file is needed by a given primitive because all
1318   variables are global, a period (`.') can be given in
1319   place of the file name.
1320   It is also possible to give an expression instead of a straight
1321 < variable name in a scene file, although such expressions should
1322 < be kept simple if possible.
1244 < Also, functions (requiring parameters)
1321 > variable name in a scene file.
1322 > Functions (requiring parameters)
1323   must be given as names and not as expressions.
1324   .PP
1325   Constant expressions are used as an optimization in function
# Line 1405 | Line 1483 | converts a picture to and from simpler formats.
1483   Pictures may be displayed directly under X11 using the program
1484   .I ximage,
1485   or converted a standard image format.
1486 < .I Ra_avs
1487 < converts to and from AVS image format.
1410 < .I Ra_pict
1411 < converts to Macintosh 32-bit PICT2 format.
1486 > .I Ra_bmp
1487 > converts to and from Microsoft Bitmap images.
1488   .I Ra_ppm
1489   converts to and from Poskanzer Portable Pixmap formats.
1414 – .I Ra_pr
1415 – converts to and from Sun 8-bit rasterfile format.
1416 – .I Ra_pr24
1417 – converts to and from Sun 24-bit rasterfile format.
1490   .I Ra_ps
1491   converts to PostScript color and greyscale formats.
1492   .I Ra_rgbe
# Line 1433 | Line 1505 | License
1505   .DS
1506   The Radiance Software License, Version 1.0
1507  
1508 < Copyright (c) 1990 - 2002 The Regents of the University of California,
1508 > Copyright (c) 1990 - 2008 The Regents of the University of California,
1509   through Lawrence Berkeley National Laboratory.   All rights reserved.
1510  
1511   Redistribution and use in source and binary forms, with or without
# Line 1495 | Line 1567 | the Ecole Polytechnique Federale de Lausanne (EPFL Uni
1567   in Lausanne, Switzerland.
1568   .NH 1
1569   References
1570 + .LP
1571 + Ward, G., M. Kurt & N. Bonneel,
1572 + ``Reducing Anisotropic BSDF Measurement to Common Practice,''
1573 + .I Workshop on Material Appearance Modeling,
1574 + 2014.
1575 + .LP
1576 + McNeil, A., C.J. Jonsson, D. Appelfeld, G. Ward, E.S. Lee,
1577 + ``A validation of a ray-tracing tool used to generate
1578 + bi-directional scattering distribution functions for
1579 + complex fenestration systems,''
1580 + .I "Solar Energy",
1581 + 98, 404-14, November 2013.
1582 + .LP
1583 + Ward, G., R. Mistrick, E.S. Lee, A. McNeil, J. Jonsson,
1584 + ``Simulating the Daylight Performance of Complex Fenestration Systems
1585 + Using Bidirectional Scattering Distribution Functions within Radiance,''
1586 + .I "Leukos",
1587 + 7(4),
1588 + April 2011.
1589 + .LP
1590 + Cater, K., A. Chalmers, G. Ward,
1591 + ``Detail to Attention: Exploiting Visual Tasks for Selective Rendering,''
1592 + .I "Eurograhics Symposium on Rendering",
1593 + June 2003.
1594   .LP
1595   Ward, G., Elena Eydelberg-Vileshin,
1596   ``Picture Perfect RGB Rendering Using Spectral Prefiltering and

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