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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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The RADIANCE 4.0 Synthetic Imaging System |
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The RADIANCE 4.1 Synthetic Imaging System |
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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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The sign of the thickness is important, as it indicates |
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whether the proxied geometry is behind the BSDF |
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surface (when thickness is positive) or in front (when |
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thickness is negative). |
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<p> |
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The second string argument is the name of the BSDF file, |
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which is found in the usual auxiliary locations. The |
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following three string parameters name variables for an |
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"up" vector, which together with the surface |
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normal, define the local coordinate system that orients the |
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BSDF. These variables, along with the thickness, are defined |
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in a function file given as the next string argument. An |
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optional transform is used to scale the thickness and |
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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 |
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to determine reflection and transmission. If there are at |
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least 3 real arguments, the first triplet is an additional |
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diffuse reflectance for the front side. At least 6 real |
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arguments adds diffuse reflectance to the rear side of the |
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surface. If there are 9 real arguments, the final triplet |
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will be taken as an additional diffuse transmittance. All |
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diffuse components as well as the non-diffuse transmission |
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are modified by patterns applied to this material. The |
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non-diffuse reflection from either side are unaffected. |
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Textures perturb the effective surface normal in the usual |
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way. |
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<p> |
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The surface normal of this type is not altered to face the |
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incoming ray, so the front and back BSDF reflections may |
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differ. (Transmission is identical front-to-back by physical |
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law.) If back visibility is turned off during rendering and |
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there is no transmission or back-side reflection, only then |
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the surface will be invisible from behind. Unlike other |
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data-driven material types, the BSDF type is fully supported |
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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> |
