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HK documentation updates

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Wenzel Jakob 2011-08-02 16:51:27 -04:00
parent 11d3e3a997
commit f8ee9e649a
1 changed files with 23 additions and 8 deletions
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src/bsdfs/hk.cpp
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@ -37,7 +37,7 @@ MTS_NAMESPACE_BEGIN
* \parameter{sigmaA}{\Spectrum\Or\Texture}{Specifies the absorption coefficient
* of the internal layer. \default{based on \code{material}}}
* \parameter{thickness}{\Float}{Denotes the thickness of the layer.
* Should be specified in inverse units of \code{sigmaA} and \code{sigmaS})\default{1}}
* (should be specified in inverse units of \code{sigmaA} and \code{sigmaS})\default{1}}
* \parameter{\Unnamed}{\Phase}{A nested phase function instance that represents
* the type of scattering interactions occurring within the layer}
* }
@ -45,12 +45,18 @@ MTS_NAMESPACE_BEGIN
* \renderings{
* \rendering{An index-matched scattering layer with parameters $\sigma_s=2$, $\sigma_a=0.1$, thickness$=0.1$}{bsdf_hk_1}
* \rendering{Example of the HK model with a dielectric coating (and the \code{ketchup} material preset, see \lstref{hk-coated})}{bsdf_hk_2}
* \vspace{-3mm}
* \caption{
* \label{fig:hk-example}
* Renderings using the uncoated and coated form of the Hanrahan-Krueger model.
* }
* \vspace{1mm}
* }
*
* This plugin provides an implementation of the Hanrahan-Krueger BSDF
* \cite{Hanrahan1993Reflection} for simulating single scattering in thin
* index-matched layers filled with random scattering media.
* Apart from single scattering, the implementation also accounts for attenuated
* index-matched layers filled with a random scattering medium.
* In addition, the implementation also accounts for attenuated
* light that passes through the medium without undergoing any scattering events.
*
* This BSDF requires a phase function to model scattering interactions within the
@ -71,8 +77,15 @@ MTS_NAMESPACE_BEGIN
*
* When used in conjuction with the \pluginref{coating} plugin, it is possible
* to model refraction and reflection at the layer boundaries when the indices
* of refraction are mismatched. The combination of these two plugins
* reproduces the full model proposed in \cite{Hanrahan1993Reflection}.
* of refraction are mismatched. The combination of these two plugins then
* reproduces the full model as it was originally proposed by Hanrahan and
* Krueger \cite{Hanrahan1993Reflection}.
*
* Note that this model does not account for light that undergoes multiple
* scattering events within the layer. This leads to energy loss,
* particularly at grazing angles, which can be seen in the left-hand image of
* \figref{hk-example}. A solution is to use the \pluginref{chkms} plugin,
* which adds an approximate multiple scattering component.
*
* \begin{xml}[caption=A thin dielectric layer with measured ketchup scattering parameters, label=lst:hk-coated]
* <bsdf type="coating">
@ -87,11 +100,13 @@ MTS_NAMESPACE_BEGIN
* \end{xml}
*
* Note that when \texttt{sigmaS} = \texttt{sigmaA}$\ = 0$, or when \texttt{thickness=0},
* any geometry associated with this scattering model will be invisible.
* any geometry associated with this BSDF becomes invisible, as light will pass through
* unchanged.
*
* The implementation in Mitsuba is based on code by Tom Kazimiers and Marios Papas.
*/
* Marios Papas has kindly verified the implementation of the coated and uncoated variants
* against both a path tracer and a separate reference implementation.
*/
class HanrahanKrueger : public BSDF {
public:
HanrahanKrueger(const Properties &props) : BSDF(props) {