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.\" RCSid "$Id" |
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.\" RCSid "$Id$" |
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.\" Print using the -ms macro package |
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.DA 2/17/2011 |
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.DA 5/11/2023 |
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.LP |
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.tl """Copyright \(co 2011 Regents, University of California |
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.tl """Copyright \(co 2023 Regents, University of California |
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.sp 2 |
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.TL |
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The |
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8 red green blue spec urough vrough trans tspec |
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.DE |
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.LP |
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.UL Ashik2 |
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.PP |
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Ashik2 is the anisotropic reflectance model by Ashikhmin & Shirley. |
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The string arguments are the same as for plastic2, but the real |
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arguments have additional flexibility to specify the specular color. |
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Also, rather than roughness, specular power is used, which has no |
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physical meaning other than larger numbers are equivalent to a smoother |
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surface. |
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Unlike other material types, total reflectance is the sum of |
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diffuse and specular colors, and should be adjusted accordingly. |
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.DS |
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mod ashik2 id |
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4+ ux uy uz funcfile transform |
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0 |
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8 dred dgrn dblu sred sgrn sblu u-power v-power |
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.DE |
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.LP |
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.UL Dielectric |
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.PP |
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A dielectric material is transparent, and it refracts light |
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.PP |
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The BSDF material type loads an XML (eXtensible Markup Language) |
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file describing a bidirectional scattering distribution function. |
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– |
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Real arguments to this material may define additional |
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diffuse components that augment the BSDF data. |
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String arguments are used to define thickness for hidden |
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objects and the "up" orientation for the material. |
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String arguments are used to define thickness for proxied |
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surfaces and the "up" orientation for the material. |
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.DS |
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mod BSDF id |
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6+ thick BSDFfile ux uy uz funcfile transform |
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rbdif gbdif bbdif |
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rtdif gtdif btdif |
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.DE |
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The first string argument is a "thickness" parameter that is useful |
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for hiding detail geometry for transmitting systems, e.g., |
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complex fenestration. |
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If a view or shadow ray hits a BSDF surface with non-zero specular transmission |
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and positive thickness, the ray will pass directly through with no |
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reflection or transmission due to the BSDF. |
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The first string argument is a "thickness" parameter that may be used |
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to hide detail geometry being proxied by an aggregate BSDF material. |
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If a view or shadow ray hits a BSDF proxy with non-zero thickness, |
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it will pass directly through as if the surface were not there. |
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Similar to the illum type, this permits direct viewing and |
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shadow testing of complex geometry. |
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In contrast, a scattered ray will use the BSDF transmission, |
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offsetting transmitted sample rays by the thickness amount |
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to avoid any intervening geometry. |
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In this manner, BSDF surfaces may act as simplified stand-ins for detailed |
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system geometry, which may still be present and visible in the simulation. |
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If the BSDF has back-side reflection data, a parallel surface should be |
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specified slightly less than the given thickness away from the front surface |
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to enclose the system geometry on both sides. |
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A zero thickness implies that the BSDF geomtery is all there is, and |
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thickness is ignored if there is no transmitted component, or transmission is |
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purely diffuse. |
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The BSDF is used when a scattered (indirect) ray hits the surface, |
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and any transmitted sample rays will be offset by the thickness amount |
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to avoid the hidden geometry and gather samples from the other side. |
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In this manner, BSDF surfaces can improve the results for indirect |
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scattering from complex systems without sacrificing appearance or |
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shadow accuracy. |
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If the BSDF has transmission and back-side reflection data, |
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a parallel BSDF surface may be |
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placed slightly less than the given thickness away from the front surface |
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to enclose the complex geometry on both sides. |
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The sign of the thickness is important, as it indicates whether the |
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proxied geometry is behind the BSDF surface (when thickness is positive) |
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or in front (when thickness is negative). |
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.LP |
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The second string argument is the name of the BSDF file, which is |
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found in the usual auxiliary locations. |
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Unlike other data-driven material types, the BSDF type is fully |
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supported and all parts of the distribution are properly sampled. |
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.LP |
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.UL aBSDF |
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.PP |
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The aBSDF material is identical to the BSDF type with two important |
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differences. |
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First, proxy geometry is not supported, so there is no thickness parameter. |
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Second, an aBSDF is assumed to have some specular through component |
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(the 'a' stands for "aperture"), which |
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is treated specially during the direct calculation and when viewing the |
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material. |
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Based on the BSDF data, the coefficient of specular transmission is |
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determined and used for modifying unscattered shadow and view rays. |
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.DS |
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mod aBSDF id |
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5+ BSDFfile ux uy uz funcfile transform |
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0 |
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0|3|6|9 |
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rfdif gfdif bfdif |
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rbdif gbdif bbdif |
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rtdif gtdif btdif |
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.DE |
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.LP |
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If a material has no specular transmitted component, it is much better |
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to use the BSDF type with a zero thickness than to use aBSDF. |
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.LP |
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.UL Antimatter |
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.PP |
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Antimatter is a material that can "subtract" volumes from other volumes. |
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The first modifier will also be used to shade the area leaving the |
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antimatter volume and entering the regular volume. |
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If mod1 is void, the antimatter volume is completely invisible. |
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Antimatter does not work properly with the material type "trans", |
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and multiple antimatter surfaces should be disjoint. |
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If shading is desired at antimatter surfaces, it is important |
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that the related volumes are closed with outward-facing normals. |
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Antimatter surfaces should not intersect with other antimatter boundaries, |
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and it is unwise to use the same modifier in nested antimatter volumes. |
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The viewpoint must be outside all volumes concerned for a correct |
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rendering. |
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.NH 3 |
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Mixtures |
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.PP |
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A mixture is a blend of one or more materials or textures and patterns. |
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Blended materials should not be light source types or virtual source types. |
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The basic types are given below. |
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.LP |
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.UL Mixfunc |
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in Lausanne, Switzerland. |
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.NH 1 |
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References |
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+ |
.LP |
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+ |
Ward, Gregory J., Bruno Bueno, David Geisler-Moroder, |
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+ |
Lars O. Grobe, Jacob C. Jonsson, Eleanor |
| 1601 |
+ |
S. Lee, Taoning Wang, Helen Rose Wilson, |
| 1602 |
+ |
``Daylight Simulation Workflows Incorporating |
| 1603 |
+ |
Measured Bidirectional Scattering Distribution Functions,'' |
| 1604 |
+ |
.I "Energy & Buildings", |
| 1605 |
+ |
Vol. 259, No. 111890, 2022. |
| 1606 |
+ |
.LP |
| 1607 |
+ |
Wang, Taoning, Gregory Ward, Eleanor Lee, |
| 1608 |
+ |
``Efficient modeling of optically-complex, non-coplanar |
| 1609 |
+ |
exterior shading: Validation of matrix algebraic methods,'' |
| 1610 |
+ |
.I "Energy & Buildings", |
| 1611 |
+ |
vol. 174, pp. 464-83, Sept. 2018. |
| 1612 |
+ |
.LP |
| 1613 |
+ |
Lee, Eleanor S., David Geisler-Moroder, Gregory Ward, |
| 1614 |
+ |
``Modeling the direct sun component in buildings using matrix |
| 1615 |
+ |
algebraic approaches: Methods and validation,'' |
| 1616 |
+ |
.I Solar Energy, |
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+ |
vol. 160, 15 January 2018, pp 380-395. |
| 1618 |
+ |
.LP |
| 1619 |
+ |
Ward, G., M. Kurt & N. Bonneel, |
| 1620 |
+ |
``Reducing Anisotropic BSDF Measurement to Common Practice,'' |
| 1621 |
+ |
.I Workshop on Material Appearance Modeling, |
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+ |
2014. |
| 1623 |
+ |
.LP |
| 1624 |
+ |
McNeil, A., C.J. Jonsson, D. Appelfeld, G. Ward, E.S. Lee, |
| 1625 |
+ |
``A validation of a ray-tracing tool used to generate |
| 1626 |
+ |
bi-directional scattering distribution functions for |
| 1627 |
+ |
complex fenestration systems,'' |
| 1628 |
+ |
.I "Solar Energy", |
| 1629 |
+ |
98, 404-14, November 2013. |
| 1630 |
+ |
.LP |
| 1631 |
+ |
Ward, G., R. Mistrick, E.S. Lee, A. McNeil, J. Jonsson, |
| 1632 |
+ |
``Simulating the Daylight Performance of Complex Fenestration Systems |
| 1633 |
+ |
Using Bidirectional Scattering Distribution Functions within Radiance,'' |
| 1634 |
+ |
.I "Leukos", |
| 1635 |
+ |
7(4), |
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+ |
April 2011. |
| 1637 |
|
.LP |
| 1638 |
|
Cater, K., A. Chalmers, G. Ward, |
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|
``Detail to Attention: Exploiting Visual Tasks for Selective Rendering,'' |
