cleanups
Wenzel Jakob
parent
736a8e6866
commit
dacb6f96b6
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@ -26,17 +26,20 @@ MTS_NAMESPACE_BEGIN
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* \parameters{
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* \parameter{preset}{\String}{Name of a material preset, see
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* \tblref{conductor-iors}.\!\default{\texttt{Cu} / copper}}
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* \parameter{eta}{\Spectrum}{Real part of the material's index of refraction
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* \default{based on the value of \texttt{preset}}}
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* \parameter{eta}{\Spectrum}{Real part of the material's index
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* of refraction \default{based on the value of \texttt{preset}}}
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* \parameter{k}{\Spectrum}{Imaginary part of the material's index of
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* refraction, also known as absorption coefficient.
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* \default{based on the value of \texttt{preset}}}
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* \lastparameter{specular\showbreak Reflectance}{\Spectrum\Or\Texture}{Optional
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* factor used to modulate the reflectance component\default{1.0}}
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* \lastparameter{specular\showbreak Reflectance}{\Spectrum\Or\Texture}{
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* Optional factor used to modulate the reflectance component
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* \default{1.0}}
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* }
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* \renderings{
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* \rendering{Measured copper material (the default)}{bsdf_conductor_copper.jpg}
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* \rendering{Measured gold material (\lstref{conductor-gold})}{bsdf_conductor_gold.jpg}
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* \rendering{Measured copper material (the default)}
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* {bsdf_conductor_copper.jpg}
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* \rendering{Measured gold material (\lstref{conductor-gold})}
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* {bsdf_conductor_gold.jpg}
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* }
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* This plugin implements a perfectly smooth interface to a conducting material,
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@ -50,18 +53,20 @@ MTS_NAMESPACE_BEGIN
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*
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* To faciliate the tedious task of specifying spectrally-varying index of
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* refraction information, Mitsuba ships with a set of measured data for a
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* several materials, where visible-spectrum information was publicly available\footnote{
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* These index of refraction values are identical to the data distributed with PBRT.
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* They are originally from the Luxpop database (\url{www.luxpop.com}) and
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* are based on data by Palik et al. \cite{Palik1998Handbook} and measurements
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* of atomic scattering factors made by the Center For X-Ray Optics (CXRO)
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* at Berkeley and the Lawrence Livermore National Laboratory (LLNL).
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* several materials, where visible-spectrum information was publicly
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* available\footnote{
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* These index of refraction values are identical to the data distributed
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* with PBRT. They are originally from the Luxpop database
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* (\url{www.luxpop.com}) and are based on data by Palik et al.
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* \cite{Palik1998Handbook} and measurements of atomic scattering factors
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* made by the Center For X-Ray Optics (CXRO) at Berkeley and the
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* Lawrence Livermore National Laboratory (LLNL).
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* }.
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*
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* Note that \tblref{conductor-iors} also includes several popular optical coatings, which are
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* not actually conductors. These materials can also be used with this plugin,
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* though note that the plugin will ignore any refraction component that the actual
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* material might have had.
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* Note that \tblref{conductor-iors} also includes several popular optical
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* coatings, which are not actually conductors. These materials can also
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* be used with this plugin, though note that the plugin will ignore any
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* refraction component that the actual material might have had.
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* The table also contains a few birefingent materials, which are split into
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* separate measurements correponding to their two indices of
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* refraction (named ``ordinary'' and ``extraordinary ray'').
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@ -70,7 +75,8 @@ MTS_NAMESPACE_BEGIN
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* renderings to get the most accurate results. While it also works in RGB mode,
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* the computations will be much more approximate in this case.
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*
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* \begin{xml}[caption=Material configuration for a smooth conductor with measured gold data, label=lst:conductor-gold]
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* \begin{xml}[caption=Material configuration for a smooth conductor with
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* measured gold data, label=lst:conductor-gold]
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* <shape type="...">
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* <bsdf type="conductor">
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* <string name="preset" value="Au"/>
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@ -79,7 +85,8 @@ MTS_NAMESPACE_BEGIN
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* \end{xml}
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* \vspace{5mm}
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* It is also possible to load spectrally varying index of refraction data from
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* two external files (see \secref{format-spectra} for details on the file format):
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* two external files (see \secref{format-spectra} for details on the file
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* format):
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* \begin{xml}[caption=Rendering a smooth conductor with custom data]
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* <shape type="...">
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* <bsdf type="conductor">
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@ -121,12 +128,13 @@ MTS_NAMESPACE_BEGIN
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* \end{tabular}
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* \caption{
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* \label{tbl:conductor-iors}
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* This table lists all supported material names that can be passed into the
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* \pluginref{conductor} plugin. Note that some of them are not actually
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* conductors---this is not a problem, they can be used regardless (though only
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* the reflection component and no transmission will be simulated).
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* In most cases, there are multiple entries for each material, which
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* represent different measurements.
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* This table lists all supported materials that can be passed into the
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* \pluginref{conductor} and \pluginref{roughconductor} plugins. Note that
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* some of them are not actually conductors---this is not a problem,
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* they can be used regardless (though only the reflection component and
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* no transmission will be simulated). In most cases, there are
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* multiple entries for each material, which represent measurements by
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* different authors.
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* }
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* \end{table}
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*/
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@ -196,9 +204,12 @@ public:
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bool sampleReflection = (bRec.typeMask & EDeltaReflection)
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&& (bRec.component == -1 || bRec.component == 0);
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/* Verify that the provided direction pair matches an ideal
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specular reflection; tolerate some roundoff errors */
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if (!sampleReflection || measure != EDiscrete ||
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Frame::cosTheta(bRec.wi) <= 0 ||
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Frame::cosTheta(bRec.wo) <= 0)
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Frame::cosTheta(bRec.wo) <= 0 ||
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std::abs(1 - dot(reflect(bRec.wi), bRec.wo)) > Epsilon)
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return Spectrum(0.0f);
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return m_specularReflectance->getValue(bRec.its) *
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@ -208,10 +219,15 @@ public:
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Float pdf(const BSDFQueryRecord &bRec, EMeasure measure) const {
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bool sampleReflection = (bRec.typeMask & EDeltaReflection)
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&& (bRec.component == -1 || bRec.component == 0);
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if (!sampleReflection || measure != EDiscrete ||
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/* Verify that the provided direction pair matches an ideal
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specular reflection; tolerate some roundoff errors */
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if (!sampleReflection || measure != EDiscrete ||
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Frame::cosTheta(bRec.wi) <= 0 ||
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Frame::cosTheta(bRec.wo) <= 0)
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Frame::cosTheta(bRec.wo) <= 0 ||
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std::abs(1 - dot(reflect(bRec.wi), bRec.wo)) > Epsilon)
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return 0.0f;
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return 1.0f;
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}
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@ -45,14 +45,14 @@ MTS_NAMESPACE_BEGIN
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*
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* This plugin models an interface between two dielectric materials having mismatched
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* indices of refraction (for instance, water and air). Exterior and interior IOR values
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* can each be independently specified, where ``exterior'' refers to the side that contains
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* can be independently specified, where ``exterior'' refers to the side that contains
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* the surface normal. When no parameters are given, the plugin activates the defaults, which
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* describe a borosilicate glass BK7/air interface.
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*
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* In this model, the microscopic surface structure of the surface is assumed to be perfectly
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* In this model, the microscopic structure of the surface is assumed to be perfectly
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* smooth, resulting in a degenerate\footnote{Meaning that for any given incoming ray of light,
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* the model always scatters into a discrete set of directions, as opposed to a continuum.}
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* BSDF described by a Dirac delta function. For a similar model that instead describes a
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* BSDF described by a Dirac delta distribution. For a similar model that instead describes a
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* rough surface microstructure, take a look at the \pluginref{roughdielectric} plugin.
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*
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* \begin{xml}[caption=A simple air-to-water interface, label=lst:dielectric-water]
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@ -125,9 +125,13 @@ MTS_NAMESPACE_BEGIN
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* \end{tabular}
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* \caption{
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* \label{tbl:dielectric-iors}
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* This table lists all supported material names that can be passed
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* into the \pluginref{dielectric} plugin, along with the associated
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* index of refraction at standard conditions.
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* This table lists all supported material names along with
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* along with the associated index of refraction at
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* standard conditions. These can be used with the plugins
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* \pluginref{dielectric},\
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* \pluginref{roughdielectric},\
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* \pluginref{plastic}, and
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* \pluginref{roughplastic}.
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* }
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* \end{table}
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*/
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@ -200,26 +204,66 @@ public:
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return Vector(-wi.x, -wi.y, wi.z);
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}
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/// Refraction in local coordinates
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/// Refraction in local coordinates (reuses computed information)
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inline Vector refract(const Vector &wi, Float eta, Float cosThetaT) const {
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return Vector(-eta*wi.x, -eta*wi.y, cosThetaT);
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}
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/// Refraction in local coordinates (full version)
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inline Vector refract(const Vector &wi) const {
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Float cosThetaI = Frame::cosTheta(wi),
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etaI = m_extIOR,
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etaT = m_intIOR;
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bool entering = cosThetaI > 0.0f;
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/* Determine the respective indices of refraction */
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if (!entering)
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std::swap(etaI, etaT);
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/* Using Snell's law, calculate the squared sine of the
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angle between the normal and the transmitted ray */
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Float eta = etaI / etaT,
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sinThetaTSqr = eta*eta * Frame::sinTheta2(wi);
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Float cosThetaT = 0;
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if (sinThetaTSqr >= 1.0f) {
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/* Total internal reflection */
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return Vector(0.0f);
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} else {
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cosThetaT = std::sqrt(1.0f - sinThetaTSqr);
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if (entering)
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cosThetaT = -cosThetaT;
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}
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return Vector(-eta*wi.x, -eta*wi.y, cosThetaT);
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}
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Spectrum eval(const BSDFQueryRecord &bRec, EMeasure measure) const {
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bool sampleReflection = (bRec.typeMask & EDeltaReflection)
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&& (bRec.component == -1 || bRec.component == 0);
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bool sampleTransmission = (bRec.typeMask & EDeltaTransmission)
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&& (bRec.component == -1 || bRec.component == 1);
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bool reflection = Frame::cosTheta(bRec.wo) * Frame::cosTheta(bRec.wi) > 0;
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if ((reflection && !sampleReflection) ||
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(!reflection && !sampleTransmission) || measure != EDiscrete)
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/* Check if the provided direction pair matches an ideal
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specular reflection; tolerate some roundoff errors */
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bool reflection = std::abs(1 - dot(reflect(bRec.wi), bRec.wo)) < Epsilon;
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if (measure != EDiscrete || (reflection && !sampleReflection))
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return Spectrum(0.0f);
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Float fr = fresnel(Frame::cosTheta(bRec.wi), m_extIOR, m_intIOR);
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if (!reflection) {
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/* Check if the provided direction pair matches an ideal
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specular refraction; tolerate some roundoff errors */
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bool refraction = std::abs(1 - dot(refract(bRec.wi), bRec.wo)) < Epsilon;
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if (!refraction || !sampleTransmission)
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return Spectrum(0.0f);
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}
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Float Fr = fresnel(Frame::cosTheta(bRec.wi), m_extIOR, m_intIOR);
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if (reflection) {
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return m_specularReflectance->getValue(bRec.its) * fr;
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return m_specularReflectance->getValue(bRec.its) * Fr;
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} else {
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Float etaI = m_extIOR, etaT = m_intIOR;
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bool entering = Frame::cosTheta(bRec.wi) > 0.0f;
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@ -229,7 +273,7 @@ public:
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Float factor = (bRec.quantity == ERadiance)
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? (etaI*etaI) / (etaT*etaT) : 1.0f;
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return m_specularTransmittance->getValue(bRec.its) * factor * (1 - fr);
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return m_specularTransmittance->getValue(bRec.its) * factor * (1 - Fr);
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}
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}
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@ -238,13 +282,21 @@ public:
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&& (bRec.component == -1 || bRec.component == 0);
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bool sampleTransmission = (bRec.typeMask & EDeltaTransmission)
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&& (bRec.component == -1 || bRec.component == 1);
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bool reflection = Frame::cosTheta(bRec.wo)
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* Frame::cosTheta(bRec.wi) > 0;
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if ((reflection && !sampleReflection) ||
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(!reflection && !sampleTransmission) || measure != EDiscrete)
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/* Check if the provided direction pair matches an ideal
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specular reflection; tolerate some roundoff errors */
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bool reflection = std::abs(1 - dot(reflect(bRec.wi), bRec.wo)) < Epsilon;
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if (measure != EDiscrete || (reflection && !sampleReflection))
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return 0.0f;
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if (!reflection) {
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/* Check if the provided direction pair matches an ideal
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specular refraction; tolerate some roundoff errors */
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bool refraction = std::abs(1 - dot(refract(bRec.wi), bRec.wo)) < Epsilon;
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if (!refraction || !sampleTransmission)
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return 0.0f;
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}
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if (sampleTransmission && sampleReflection) {
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Float Fr = fresnel(Frame::cosTheta(bRec.wi), m_extIOR, m_intIOR);
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return reflection ? Fr : (1 - Fr);
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@ -43,10 +43,9 @@ MTS_NAMESPACE_BEGIN
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* behavior than the separately available \pluginref{phong} plugin.
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* \item \code{ggx}: New distribution proposed by
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* Walter et al. meant to better handle the long
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* tails observed in transmission measurements through
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* ground glass. Renderings with this distribution may
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* converge slowly.
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* \item \code{as}: Anisotropic microfacet distribution proposed by
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* tails observed in measurements of ground surfaces.
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* Renderings with this distribution may converge slowly.
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* \item \code{as}: Anisotropic Phong-style microfacet distribution proposed by
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* Ashikhmin and Shirley \cite{Ashikhmin2005Anisotropic}.\vspace{-3mm}
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* \end{enumerate}
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* }
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@ -58,12 +57,14 @@ MTS_NAMESPACE_BEGIN
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* \default{0.1}.
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* }
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* \parameter{alphaU, alphaV}{\Float\Or\Texture}{
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* Specifies the anisotropic rougness values along the tangent and bitangent directions. This
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* parameter is only valid when \texttt{distribution=as}.
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* Specifies the anisotropic rougness values along the tangent and bitangent directions. These
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* parameter are only valid when \texttt{distribution=as}.
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* \default{0.1}.
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* }
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* \parameter{intIOR}{\Float}{Interior index of refraction \default{1.5046}}
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* \parameter{extIOR}{\Float}{Exterior index of refraction \default{1.0}}
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* \parameter{intIOR}{\Float\Or\String}{Interior index of refraction specified
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* numerically or using a known material name. \default{\texttt{bk7} / 1.5046}}
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* \parameter{extIOR}{\Float\Or\String}{Exterior index of refraction specified
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* numerically or using a known material name. \default{\texttt{air} / 1.000277}}
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* \parameter{specular\showbreak Reflectance}{\Spectrum\Or\Texture}{Optional
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* factor used to modulate the reflectance component\default{1.0}}
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* \lastparameter{specular\showbreak Transmittance}{\Spectrum\Or\Texture}{Optional
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@ -93,39 +94,43 @@ MTS_NAMESPACE_BEGIN
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* plugin is based on the paper ``Microfacet Models for Refraction through
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* Rough Surfaces'' by Walter et al. \cite{Walter07Microfacet}. It supports
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* several types of microfacet distributions and has a texturable roughness
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* parameter. Exterior and interior IOR values can each be independently
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* parameter. Exterior and interior IOR values can be independently
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* specified, where ``exterior'' refers to the side that contains the surface
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* normal. When no parameters are given, the plugin activates the default
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* settings, which describe a borosilicate glass BK7/air interface with a
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* light amount of roughness modeled using a Beckmann distribution.
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* normal. Similar to the \pluginref{dielectric} plugin, IOR values can either
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* be specified numerically, or based on a list of known materials (see
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* \tblref{dielectric-iors} for an overview). When no parameters are given,
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* the plugin activates the default settings, which describe a borosilicate
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* glass BK7/air interface with a light amount of roughness modeled using a
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* Beckmann distribution.
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*
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* When using the Ashikmin-Shirley or Phong models, a conversion method is
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* used to turn the specified $\alpha$ roughness value into the exponents
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* of these distributions. This is done so that the different distributions
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* all produce a similar appearance for the same value of $\alpha$.
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* of these distributions. This is done in a way, such that the different
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* distributions all produce a similar appearance for the same value of $\alpha$.
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*
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* When using this plugin, it is crucial that the scene contains
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* meaningful and mutally compatible index of refraction changes---see
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* \figref{glass-explanation} for an example. Also, please note that
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* the importance sampling implementation of this model is close, but
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* not perfect a perfect match to the underlying scattering distribution,
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* particularly for high roughness values and when the \texttt{GGX}
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* model is used. Hence, such renderings may converge slowly.\vspace{1cm}
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* not always a perfect a perfect match to the underlying scattering distribution,
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* particularly for high roughness values and when the \texttt{ggx}
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* microfacet distribution is used. Hence, such renderings may
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* converge slowly.\vspace{1cm}
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*
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* \begin{xml}[caption=Material definition for ground glass, label=lst:roughdielectric-roughglass]
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* \begin{xml}[caption=A material definition for ground glass, label=lst:roughdielectric-roughglass]
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* <bsdf type="roughdielectric">
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* <string name="distribution" value="ggx"/>
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* <float name="alpha" value="0.304"/>
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* <float name="intIOR" value="1.5046"/>
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* <float name="extIOR" value="1.0"/>
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* <string name="intIOR" value="bk7"/>
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* <string name="extIOR" value="air"/>
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* </bsdf>
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* \end{xml}
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*
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* \begin{xml}[caption=A texture can be attached to the roughness parameter, label=lst:roughdielectric-textured]
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* <bsdf type="roughdielectric">
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* <string name="distribution" value="beckmann"/>
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* <string name="intIOR" value="bk7"/>
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* <string name="extIOR" value="air"/>
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* <float name="intIOR" value="1.5046"/>
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* <float name="extIOR" value="1.0"/>
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*
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* <texture name="alpha" type="bitmap">
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* <string name="filename" value="roughness.exr"/>
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Reference in New Issue