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.\" RCSid "$Id$" |
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.\" Print using the -ms macro package |
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.DA 1/20/99 |
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.DA 07/10/2016 |
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.LP |
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< |
.tl """Copyright \(co 2003 Regents, University of California |
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.tl """Copyright \(co 2017 Regents, University of California |
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.sp 2 |
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.TL |
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The |
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.LP |
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.UL Mirror |
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.PP |
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Mirror is used for planar surfaces that produce secondary |
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Mirror is used for planar surfaces that produce virtual |
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source reflections. |
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This material should be used sparingly, as it may cause the light |
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source calculation to blow up if it is applied to many small surfaces. |
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.UL Prism1 |
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.PP |
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The prism1 material is for general light redirection from prismatic |
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glazings, generating secondary light sources. |
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glazings, generating virtual light sources. |
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It can only be used to modify a planar surface (i.e., a polygon or disk) |
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and should not result in either light concentration or scattering. |
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The new direction of the ray can be on either side of the material, |
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and the definitions must have the correct bidirectional properties |
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to work properly with secondary light sources. |
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to work properly with virtual light sources. |
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The arguments give the coefficient for the redirected light |
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and its direction. |
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.DS |
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The scattering eccentricity parameter will likewise override the global |
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setting if it is present. |
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Scattering eccentricity indicates how much scattered light favors the |
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forward direction, as fit by the Heyney-Greenstein function: |
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forward direction, as fit by the Henyey-Greenstein function: |
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.DS |
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P(theta) = (1 - g*g) / (1 + g*g - 2*g*cos(theta))^1.5 |
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.DE |
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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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.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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6+ red green blue rspec trans tspec A7 .. |
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.DE |
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.LP |
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.UL BSDF |
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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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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 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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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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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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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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The following three string parameters name variables for an "up" vector, |
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which together with the surface normal, define the |
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local coordinate system that orients the BSDF. |
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These variables, along with the thickness, are defined in a function |
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file given as the next string argument. |
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An optional transform is used to scale the thickness and reorient the up vector. |
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.LP |
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If no real arguments are given, the BSDF is used by itself to determine |
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reflection and transmission. |
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If there are at least 3 real arguments, the first triplet is an |
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additional diffuse reflectance for the front side. |
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At least 6 real arguments adds diffuse reflectance to the rear side of the surface. |
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If there are 9 real arguments, the final triplet will be taken as an additional |
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diffuse transmittance. |
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All diffuse components as well as the non-diffuse transmission are |
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modified by patterns applied to this material. |
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The non-diffuse reflection from either side are unaffected. |
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Textures perturb the effective surface normal in the usual way. |
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.LP |
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The surface normal of this type is not altered to face the incoming ray, |
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so the front and back BSDF reflections may differ. |
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(Transmission is identical front-to-back by physical law.)\0 |
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If back visibility is turned off during rendering and there is no |
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transmission or back-side reflection, only then the surface will be |
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invisible from behind. |
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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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Vname is the coefficient defined in funcfile that determines the influence |
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of foreground. |
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The background coefficient is always (1-vname). |
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Since the references are not resolved until runtime, the last |
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definitions of the modifier id's will be used. |
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This can result in modifier loops, which are detected by the |
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renderer. |
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.LP |
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.UL Mixdata |
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.PP |
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variables are global, a period (`.') can be given in |
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place of the file name. |
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It is also possible to give an expression instead of a straight |
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variable name in a scene file, although such expressions should |
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be kept simple if possible. |
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Also, functions (requiring parameters) |
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variable name in a scene file. |
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Functions (requiring parameters) |
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must be given as names and not as expressions. |
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.PP |
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Constant expressions are used as an optimization in function |
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.I Rview |
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is ray-tracing program for viewing a scene interactively. |
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When the user specifies a new perspective, |
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.I rvu |
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> |
.I rview |
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quickly displays a rough |
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image on the terminal, then progressively |
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increases the resolution as the user looks on. |
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Pictures may be displayed directly under X11 using the program |
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.I ximage, |
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or converted a standard image format. |
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.I Ra_avs |
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converts to and from AVS image format. |
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.I Ra_pict |
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converts to Macintosh 32-bit PICT2 format. |
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> |
.I Ra_bmp |
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converts to and from Microsoft Bitmap images. |
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.I Ra_ppm |
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converts to and from Poskanzer Portable Pixmap formats. |
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– |
.I Ra_pr |
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converts to and from Sun 8-bit rasterfile format. |
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.I Ra_pr24 |
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converts to and from Sun 24-bit rasterfile format. |
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.I Ra_ps |
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converts to PostScript color and greyscale formats. |
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.I Ra_rgbe |
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.DS |
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The Radiance Software License, Version 1.0 |
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|
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< |
Copyright (c) 1990 - 2002 The Regents of the University of California, |
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> |
Copyright (c) 1990 - 2008 The Regents of the University of California, |
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through Lawrence Berkeley National Laboratory. All rights reserved. |
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|
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Redistribution and use in source and binary forms, with or without |
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in Lausanne, Switzerland. |
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.NH 1 |
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References |
| 1596 |
+ |
.LP |
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+ |
Wang, Taoning, Gregory Ward, Eleanor Lee, |
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+ |
``Efficient modeling of optically-complex, non-coplanar |
| 1599 |
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exterior shading: Validation of matrix algebraic methods,'' |
| 1600 |
+ |
.I "Energy & Buildings", |
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vol. 174, pp. 464-83, Sept. 2018. |
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+ |
.LP |
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Lee, Eleanor S., David Geisler-Moroder, Gregory Ward, |
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``Modeling the direct sun component in buildings using matrix |
| 1605 |
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algebraic approaches: Methods and validation,'' |
| 1606 |
+ |
.I Solar Energy, |
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vol. 160, 15 January 2018, pp 380-395. |
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+ |
.LP |
| 1609 |
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Ward, G., M. Kurt & N. Bonneel, |
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``Reducing Anisotropic BSDF Measurement to Common Practice,'' |
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+ |
.I Workshop on Material Appearance Modeling, |
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+ |
2014. |
| 1613 |
+ |
.LP |
| 1614 |
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McNeil, A., C.J. Jonsson, D. Appelfeld, G. Ward, E.S. Lee, |
| 1615 |
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``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", |
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+ |
98, 404-14, November 2013. |
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+ |
.LP |
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+ |
Ward, G., R. Mistrick, E.S. Lee, A. McNeil, J. Jonsson, |
| 1622 |
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``Simulating the Daylight Performance of Complex Fenestration Systems |
| 1623 |
+ |
Using Bidirectional Scattering Distribution Functions within Radiance,'' |
| 1624 |
+ |
.I "Leukos", |
| 1625 |
+ |
7(4), |
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+ |
April 2011. |
| 1627 |
+ |
.LP |
| 1628 |
+ |
Cater, K., A. Chalmers, G. Ward, |
| 1629 |
+ |
``Detail to Attention: Exploiting Visual Tasks for Selective Rendering,'' |
| 1630 |
+ |
.I "Eurograhics Symposium on Rendering", |
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+ |
June 2003. |
| 1632 |
|
.LP |
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|
Ward, G., Elena Eydelberg-Vileshin, |
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``Picture Perfect RGB Rendering Using Spectral Prefiltering and |
