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Revision 1.16 by greg, Fri Mar 12 18:43:30 2010 UTC vs.
Revision 1.36 by greg, Mon Oct 8 20:04:09 2018 UTC

# Line 1 | Line 1
1 < .\" RCSid "$Id"
1 > .\" RCSid "$Id$"
2   .\" Print using the -ms macro package
3 < .DA 3/12/2010
3 > .DA 07/10/2016
4   .LP
5 < .tl """Copyright \(co 2010 Regents, University of California
5 > .tl """Copyright \(co 2017 Regents, University of California
6   .sp 2
7   .TL
8   The
# 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 aBSDF
951 + .PP
952 + The aBSDF material is identical to the BSDF type with two important
953 + differences.
954 + First, proxy geometry is not supported, so there is no thickness parameter.
955 + Second, an aBSDF is assumed to have some specular through component
956 + (the 'a' stands for "aperture"), which
957 + is treated specially during the direct calculation and when viewing the
958 + material.
959 + Based on the BSDF data, the coefficient of specular transmission is
960 + determined and used for modifying unscattered shadow and view rays.
961 + .DS
962 + mod aBSDF id
963 + 5+ BSDFfile ux uy uz funcfile transform
964 + 0
965 + 0|3|6|9
966 +     rfdif gfdif bfdif
967 +     rbdif gbdif bbdif
968 +     rtdif gtdif btdif
969 + .DE
970 + .LP
971 + If a material has no specular transmitted component, it is much better
972 + to use the BSDF type with a zero thickness than to use aBSDF.
973 + .LP
974   .UL Antimatter
975   .PP
976   Antimatter is a material that can "subtract" volumes from other volumes.
# Line 879 | Line 985 | N mod1 mod2 .. modN
985   The first modifier will also be used to shade the area leaving the
986   antimatter volume and entering the regular volume.
987   If mod1 is void, the antimatter volume is completely invisible.
988 < Antimatter does not work properly with the material type "trans",
989 < and multiple antimatter surfaces should be disjoint.
988 > If shading is desired at antimatter surfaces, it is important
989 > that the related volumes are closed with outward-facing normals.
990 > Antimatter surfaces should not intersect with other antimatter boundaries,
991 > and it is unwise to use the same modifier in nested antimatter volumes.
992   The viewpoint must be outside all volumes concerned for a correct
993   rendering.
994   .NH 3
# Line 1088 | Line 1196 | between 0.1 (for tightly spaced characters) and 0.3 (f
1196   Mixtures
1197   .PP
1198   A mixture is a blend of one or more materials or textures and patterns.
1199 + Blended materials should not be light source types or virtual source types.
1200   The basic types are given below.
1201   .LP
1202   .UL Mixfunc
# Line 1400 | Line 1509 | converts a picture to and from simpler formats.
1509   Pictures may be displayed directly under X11 using the program
1510   .I ximage,
1511   or converted a standard image format.
1512 < .I Ra_avs
1513 < converts to and from AVS image format.
1405 < .I Ra_pict
1406 < converts to Macintosh 32-bit PICT2 format.
1512 > .I Ra_bmp
1513 > converts to and from Microsoft Bitmap images.
1514   .I Ra_ppm
1515   converts to and from Poskanzer Portable Pixmap formats.
1409 – .I Ra_pr
1410 – converts to and from Sun 8-bit rasterfile format.
1411 – .I Ra_pr24
1412 – converts to and from Sun 24-bit rasterfile format.
1516   .I Ra_ps
1517   converts to PostScript color and greyscale formats.
1518   .I Ra_rgbe
# Line 1490 | Line 1593 | the Ecole Polytechnique Federale de Lausanne (EPFL Uni
1593   in Lausanne, Switzerland.
1594   .NH 1
1595   References
1596 + .LP
1597 + Wang, Taoning, Gregory Ward, Eleanor Lee,
1598 + ``Efficient modeling of optically-complex, non-coplanar
1599 + exterior shading: Validation of matrix algebraic methods,''
1600 + .I "Energy & Buildings",
1601 + vol. 174, pp. 464-83, Sept. 2018.
1602 + .LP
1603 + Lee, Eleanor S., David Geisler-Moroder, Gregory Ward,
1604 + ``Modeling the direct sun component in buildings using matrix
1605 + algebraic approaches: Methods and validation,''
1606 + .I Solar Energy,
1607 + vol. 160, 15 January 2018, pp 380-395.
1608 + .LP
1609 + Ward, G., M. Kurt & N. Bonneel,
1610 + ``Reducing Anisotropic BSDF Measurement to Common Practice,''
1611 + .I Workshop on Material Appearance Modeling,
1612 + 2014.
1613 + .LP
1614 + McNeil, A., C.J. Jonsson, D. Appelfeld, G. Ward, E.S. Lee,
1615 + ``A validation of a ray-tracing tool used to generate
1616 + bi-directional scattering distribution functions for
1617 + complex fenestration systems,''
1618 + .I "Solar Energy",
1619 + 98, 404-14, November 2013.
1620 + .LP
1621 + Ward, G., R. Mistrick, E.S. Lee, A. McNeil, J. Jonsson,
1622 + ``Simulating the Daylight Performance of Complex Fenestration Systems
1623 + Using Bidirectional Scattering Distribution Functions within Radiance,''
1624 + .I "Leukos",
1625 + 7(4),
1626 + April 2011.
1627   .LP
1628   Cater, K., A. Chalmers, G. Ward,
1629   ``Detail to Attention: Exploiting Visual Tasks for Selective Rendering,''

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