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Revision 1.9 by greg, Wed May 10 19:50:30 2006 UTC vs.
Revision 1.29 by greg, Wed May 25 18:52:45 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 09/18/2015
4   .LP
5 < .tl """Copyright \(co 2003 Regents, University of California
5 > .tl """Copyright \(co 2015 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 865 | Line 865 | mod transdata id
865   6+ red green blue rspec trans tspec A7 ..
866   .DE
867   .LP
868 + .UL BSDF
869 + .PP
870 + The BSDF material type loads an XML (eXtensible Markup Language)
871 + file describing a bidirectional scattering distribution function.
872 + Real arguments to this material may define additional
873 + diffuse components that augment the BSDF data.
874 + String arguments are used to define thickness for proxied
875 + surfaces and the "up" orientation for the material.
876 + .DS
877 + mod BSDF id
878 + 6+ thick BSDFfile ux uy uz funcfile transform
879 + 0
880 + 0|3|6|9
881 +     rfdif gfdif bfdif
882 +     rbdif gbdif bbdif
883 +     rtdif gtdif btdif
884 + .DE
885 + The first string argument is a "thickness" parameter that may be used
886 + to hide detail geometry being proxied by an aggregate BSDF material.
887 + If a view or shadow ray hits a BSDF proxy with non-zero thickness,
888 + it will pass directly through as if the surface were not there.
889 + Similar to the illum type, this permits direct viewing and
890 + shadow testing of complex geometry.
891 + The BSDF is used when a scattered (indirect) ray hits the surface,
892 + and any transmitted sample rays will be offset by the thickness amount
893 + to avoid the hidden geometry and gather samples from the other side.
894 + In this manner, BSDF surfaces can improve the results for indirect
895 + scattering from complex systems without sacrificing appearance or
896 + shadow accuracy.
897 + If the BSDF has transmission and back-side reflection data,
898 + a parallel BSDF surface may be
899 + placed slightly less than the given thickness away from the front surface
900 + to enclose the complex geometry on both sides.
901 + The sign of the thickness is important, as it indicates whether the
902 + proxied geometry is behind the BSDF surface (when thickness is positive)
903 + or in front (when thickness is negative).
904 + .LP
905 + The second string argument is the name of the BSDF file, which is
906 + found in the usual auxiliary locations.
907 + The following three string parameters name variables for an "up" vector,
908 + which together with the surface normal, define the
909 + local coordinate system that orients the BSDF.
910 + These variables, along with the thickness, are defined in a function
911 + file given as the next string argument.
912 + An optional transform is used to scale the thickness and reorient the up vector.
913 + .LP
914 + If no real arguments are given, the BSDF is used by itself to determine
915 + reflection and transmission.
916 + If there are at least 3 real arguments, the first triplet is an
917 + additional diffuse reflectance for the front side.
918 + At least 6 real arguments adds diffuse reflectance to the rear side of the surface.
919 + If there are 9 real arguments, the final triplet will be taken as an additional
920 + diffuse transmittance.
921 + All diffuse components as well as the non-diffuse transmission are
922 + modified by patterns applied to this material.
923 + The non-diffuse reflection from either side are unaffected.
924 + Textures perturb the effective surface normal in the usual way.
925 + .LP
926 + The surface normal of this type is not altered to face the incoming ray,
927 + so the front and back BSDF reflections may differ.
928 + (Transmission is identical front-to-back by physical law.)\0
929 + If back visibility is turned off during rendering and there is no
930 + transmission or back-side reflection, only then the surface will be
931 + invisible from behind.
932 + Unlike other data-driven material types, the BSDF type is fully
933 + supported and all parts of the distribution are properly sampled.
934 + .LP
935   .UL Antimatter
936   .PP
937   Antimatter is a material that can "subtract" volumes from other volumes.
# Line 1088 | Line 1155 | between 0.1 (for tightly spaced characters) and 0.3 (f
1155   Mixtures
1156   .PP
1157   A mixture is a blend of one or more materials or textures and patterns.
1158 + Blended materials should not be light source types or virtual source types.
1159   The basic types are given below.
1160   .LP
1161   .UL Mixfunc
# Line 1109 | Line 1177 | which serves as a form of opacity control when used wi
1177   Vname is the coefficient defined in funcfile that determines the influence
1178   of foreground.
1179   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.
1180   .LP
1181   .UL Mixdata
1182   .PP
# Line 1239 | Line 1303 | If no file is needed by a given primitive because all
1303   variables are global, a period (`.') can be given in
1304   place of the file name.
1305   It is also possible to give an expression instead of a straight
1306 < variable name in a scene file, although such expressions should
1307 < be kept simple if possible.
1244 < Also, functions (requiring parameters)
1306 > variable name in a scene file.
1307 > Functions (requiring parameters)
1308   must be given as names and not as expressions.
1309   .PP
1310   Constant expressions are used as an optimization in function
# Line 1405 | Line 1468 | converts a picture to and from simpler formats.
1468   Pictures may be displayed directly under X11 using the program
1469   .I ximage,
1470   or converted a standard image format.
1471 < .I Ra_avs
1472 < converts to and from AVS image format.
1410 < .I Ra_pict
1411 < converts to Macintosh 32-bit PICT2 format.
1471 > .I Ra_bmp
1472 > converts to and from Microsoft Bitmap images.
1473   .I Ra_ppm
1474   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.
1475   .I Ra_ps
1476   converts to PostScript color and greyscale formats.
1477   .I Ra_rgbe
# Line 1433 | Line 1490 | License
1490   .DS
1491   The Radiance Software License, Version 1.0
1492  
1493 < Copyright (c) 1990 - 2002 The Regents of the University of California,
1493 > Copyright (c) 1990 - 2008 The Regents of the University of California,
1494   through Lawrence Berkeley National Laboratory.   All rights reserved.
1495  
1496   Redistribution and use in source and binary forms, with or without
# Line 1495 | Line 1552 | the Ecole Polytechnique Federale de Lausanne (EPFL Uni
1552   in Lausanne, Switzerland.
1553   .NH 1
1554   References
1555 + .LP
1556 + Ward, G., M. Kurt & N. Bonneel,
1557 + ``Reducing Anisotropic BSDF Measurement to Common Practice,''
1558 + .I Workshop on Material Appearance Modeling,
1559 + 2014.
1560 + .LP
1561 + McNeil, A., C.J. Jonsson, D. Appelfeld, G. Ward, E.S. Lee,
1562 + ``A validation of a ray-tracing tool used to generate
1563 + bi-directional scattering distribution functions for
1564 + complex fenestration systems,''
1565 + .I "Solar Energy",
1566 + 98, 404-14, November 2013.
1567 + .LP
1568 + Ward, G., R. Mistrick, E.S. Lee, A. McNeil, J. Jonsson,
1569 + ``Simulating the Daylight Performance of Complex Fenestration Systems
1570 + Using Bidirectional Scattering Distribution Functions within Radiance,''
1571 + .I "Leukos",
1572 + 7(4),
1573 + April 2011.
1574 + .LP
1575 + Cater, K., A. Chalmers, G. Ward,
1576 + ``Detail to Attention: Exploiting Visual Tasks for Selective Rendering,''
1577 + .I "Eurograhics Symposium on Rendering",
1578 + June 2003.
1579   .LP
1580   Ward, G., Elena Eydelberg-Vileshin,
1581   ``Picture Perfect RGB Rendering Using Spectral Prefiltering and

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