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The RADIANCE 4.0 Synthetic Imaging System |
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The RADIANCE 4.1 Synthetic Imaging System |
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<body> |
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The RADIANCE 4.0 Synthetic Imaging System |
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The RADIANCE 4.1 Synthetic Imaging System |
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</h1> |
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<dt> |
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<a NAME="BSDF"> |
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<b>BSDF</b> |
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</a> |
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<dd> |
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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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<pre> |
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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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</pre> |
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<p> |
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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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<p> |
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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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<p> |
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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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<p> |
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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.) |
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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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<p> |
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<dt> |
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<a NAME="Antimatter"> |
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<b>Antimatter</b> |
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</a> |
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<a HREF="#Plasdata">Plasdata</a> |
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<a HREF="#Metdata">Metdata</a> |
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<a HREF="#Transdata">Transdata</a> |
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<a HREF="#BSDF">BSDF</a> |
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<a HREF="#Antimatter">Antimatter</a> |
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</pre> |
