a few bugfixed, re-integrated twosided
Wenzel Jakob
parent
4871d6793a
commit
60e0252af3
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@ -8,6 +8,11 @@
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<!-- Test the rough diffuse model -->
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<bsdf type="roughdiffuse"/>
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<!-- Test the two-sided model -->
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<bsdf type="twosided">
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<bsdf type="diffuse"/>
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</bsdf>
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<!-- Test the diffuse transmission model -->
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<bsdf type="difftrans"/>
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@ -110,4 +115,5 @@
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<string name="distribution" value="beckmann"/>
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<float name="alpha" value=".7"/>
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</bsdf>
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</scene>
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12
doc/main.bib
12
doc/main.bib
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@ -46,3 +46,15 @@
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year = {1994},
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organization={ACM}
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}
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@inproceedings{Weidlich2007Arbitrarily,
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author = {Weidlich, Andrea and Wilkie, Alexander},
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title = {Arbitrarily layered micro-facet surfaces},
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booktitle = {Proceedings of the 5th international conference on Computer graphics and interactive techniques in Australia and Southeast Asia},
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series = {GRAPHITE '07},
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year = {2007},
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pages = {171--178},
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publisher = {ACM},
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address = {New York, NY, USA}
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}
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@ -12,15 +12,15 @@ plugins += env.SharedLibrary('roughplastic', ['roughplastic.cpp'])
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# Materials that act as modifiers
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#plugins += env.SharedLibrary('coating', ['coating.cpp'])
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#plugins += env.SharedLibrary('twosided', ['twosided.cpp'])
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plugins += env.SharedLibrary('twosided', ['twosided.cpp'])
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#plugins += env.SharedLibrary('mask', ['mask.cpp'])
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plugins += env.SharedLibrary('mixture', ['mixture.cpp'])
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# Other materials
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plugins += env.SharedLibrary('difftrans', ['difftrans.cpp'])
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plugins += env.SharedLibrary('phong', ['phong.cpp'])
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#plugins += env.SharedLibrary('ward', ['ward.cpp'])
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#plugins += env.SharedLibrary('phong', ['phong.cpp'])
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#plugins += env.SharedLibrary('irawan', ['irawan.cpp'])
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Export('plugins')
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@ -27,6 +27,7 @@ MTS_NAMESPACE_BEGIN
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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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* }
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* This class implements a smooth dielectric coating in the style of \cite{Weidlich2007Arbitrarily}.
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*
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* XXX cancel out cosine factors?
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* XXX did I get the measure conversion terms right?
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@ -460,7 +460,7 @@ public:
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nEvalsTotal += nEvals;
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}
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SLog(EInfo, "Created a " SIZE_T_FMT "-node cubic spline approximation to the rough Frensel "
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SLog(EInfo, "Created a " SIZE_T_FMT "-node cubic spline approximation to the rough Fresnel "
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"transmittance (integration took %i ms and " SIZE_T_FMT " function evaluations)",
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resolution, timer->getMilliseconds(), nEvalsTotal);
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spline->build();
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@ -36,6 +36,7 @@ MTS_NAMESPACE_BEGIN
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* \item \code{ggx}: New distribution proposed by
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* Walter et al. \cite{Walter07Microfacet}, which is meant to better handle
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* the long tails observed in measurements of ground surfaces.
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* Renderings with this distribution may converge slowly.
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* \item \code{phong}: Classical $\cos^p\theta$ distribution.
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* Due to the underlying microfacet theory,
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* the use of this distribution here leads to more realistic
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@ -67,13 +68,9 @@ MTS_NAMESPACE_BEGIN
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* factor used to modulate the reflectance component\default{1.0}}
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* }
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* This plugin implements a realistic microfacet scattering model for rendering
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* rough conducting materials, such as metals. Microfacet theory describes rough
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* surfaces as an arrangement of unresolved and ideally specular facets, whose
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* normal directions are given by a specially chosen \emph{microfacet distribution}.
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* By accounting for shadowing and masking effects between these facets, it is
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* possible to reproduce the important off-specular reflections peaks observed
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* in real-world measurements of such materials.
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* rough conducting materials, such as metals. It can be interpreted as a fancy
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* version of the Cook-Torrance model and should be preferred over
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* empirical models like \pluginref{phong} and \pluginref{ward} when possible.
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* \renderings{
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* \rendering{Rough copper (Beckmann, $\alpha=0.1$)}
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* {bsdf_roughconductor_copper.jpg}
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@ -81,9 +78,16 @@ MTS_NAMESPACE_BEGIN
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* $\alpha_u=0.05,\ \alpha_v=0.3$), see
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* \lstref{roughconductor-aluminium}}
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* {bsdf_roughconductor_anisotropic_aluminium.jpg}
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* \vspace{-7mm}
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* \vspace{-8mm}
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* }
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*
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* Microfacet theory describes rough
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* surfaces as an arrangement of unresolved and ideally specular facets, whose
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* normal directions are given by a specially chosen \emph{microfacet distribution}.
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* By accounting for shadowing and masking effects between these facets, it is
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* possible to reproduce the important off-specular reflections peaks observed
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* in real-world measurements of such materials.
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*
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* This plugin is essentially the ``roughened'' equivalent of the (smooth) plugin
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* \pluginref{conductor}. For very low values of $\alpha$, the two will
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* be very similar, though scenes using this plugin will take longer to render
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@ -108,8 +112,8 @@ MTS_NAMESPACE_BEGIN
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* with slight imperfections on an
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* otherwise smooth surface finish, $\alpha=0.1$ is relatively rough,
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* and $\alpha=0.3-0.7$ is \emph{extremely} rough (e.g. an etched or ground
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* finish).
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* \vspace{-2mm}
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* finish). Values significantly above that are probably not too realistic.
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* \vspace{-6mm}
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* \subsubsection*{Techical details}\vspace{-2mm}
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* When rendering with the Ashikhmin-Shirley or Phong microfacet
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* distributions, a conversion is used to turn the specified
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@ -122,7 +126,7 @@ MTS_NAMESPACE_BEGIN
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* of two distinct roughness values along the tangent and bitangent
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* directions. This can be used to provide a material with a ``brushed''
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* appearance. The alignment of the anisotropy will follow the UV
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* parameterization of the underlying mesh in this case. This means that
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* parameterization of the underlying mesh in this case. This also means that
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* such an anisotropic material cannot be applied to triangle meshes that
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* are missing texture coordinates.
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*
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@ -131,7 +135,7 @@ MTS_NAMESPACE_BEGIN
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* in RGB mode, the computations will be much more approximate in this case.
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* Also note that this material is one-sided---that is, observed from the
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* back side, it will be completely black. If this is undesirable,
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* consider using the \pluginref{twosided} BRDF adapter plugin.
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* consider using the \pluginref{twosided} BRDF adapter.
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*
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* \begin{xml}[caption={A material definition for brushed aluminium}, label=lst:roughconductor-aluminium]
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* <bsdf type="roughconductor">
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@ -310,10 +314,11 @@ public:
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const Spectrum F = fresnelConductor(Frame::cosTheta(bRec.wi),
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m_eta, m_k);
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Float numerator = m_distribution.G(bRec.wi, bRec.wo, m, alphaU, alphaV)
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Float numerator = m_distribution.eval(m, alphaU, alphaV)
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* m_distribution.G(bRec.wi, bRec.wo, m, alphaU, alphaV)
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* dot(bRec.wi, m);
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Float denominator = Frame::cosTheta(m)
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Float denominator = m_distribution.pdf(m, alphaU, alphaV)
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* Frame::cosTheta(bRec.wi);
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return m_specularReflectance->getValue(bRec.its) * F
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@ -135,7 +135,7 @@ MTS_NAMESPACE_BEGIN
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* of two distinct roughness values along the tangent and bitangent
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* directions. This can be used to provide a material with a ``brushed''
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* appearance. The alignment of the anisotropy will follow the UV
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* parameterization of the underlying mesh in this case. This means that
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* parameterization of the underlying mesh in this case. This also means that
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* such an anisotropic material cannot be applied to triangle meshes that
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* are missing texture coordinates.\newpage
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*
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@ -53,7 +53,7 @@ MTS_NAMESPACE_BEGIN
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* \default{0.1}.
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* }
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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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* numerically or using a known material name. \default{\texttt{polypropylene} / 1.49}}
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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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@ -62,10 +62,73 @@ MTS_NAMESPACE_BEGIN
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* factor used to modulate the diffuse reflectance component\default{0.5}}
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* }
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* \renderings{
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* \rendering{Beckmann, $\alpha=0.1$}{bsdf_roughplastic_ggx}
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* \rendering{GGX, $\alpha=0.3$}{bsdf_roughplastic_ggx}
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* \medrendering{Beckmann, $\alpha=0.05$, \texttt{diffuse}
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* \showbreak\texttt{Reflectance=0}, \lstref{roughplastic-lacquer}}{bsdf_roughplastic_beckmann_lacquer}
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* \medrendering{Beckmann, $\alpha=0.1$}{bsdf_roughplastic_beckmann}
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* \medrendering{GGX, $\alpha=0.3$}{bsdf_roughplastic_ggx}
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* }
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*
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* This plugin implements a realistic microfacet scattering model for rendering
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* rough dielectric materials with internal scattering, such as plastic. It can
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* be interpreted as a fancy version of the Cook-Torrance model and should be
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* preferred over empirical models like \pluginref{phong} and \pluginref{ward}
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* when possible.
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*
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* Microfacet theory describes rough surfaces as an arrangement of unresolved and
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* ideally specular facets, whose normal directions are given by a specially
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* chosen \emph{microfacet distribution}.
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* By accounting for shadowing and masking effects between these facets, it is
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* possible to reproduce the important off-specular reflections peaks observed
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* in real-world measurements of such materials.
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*
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* This plugin is essentially the ``roughened'' equivalent of the (smooth) plugin
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* \pluginref{plastic}. For very low values of $\alpha$, the two will
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* be very similar, though scenes using this plugin will take longer to render
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* due to the additional computational burden of tracking surface roughness.
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*
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* The model uses the integrated specular reflectance to interpolate between the
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* specular and diffuse components (i.e. any light that is not scattered
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* specularly is assumed to contribute to the diffuse component).
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* Similar to the \pluginref{dielectric} plugin, IOR values
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* can either be specified numerically, or based on a list of known materials
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* (see \tblref{dielectric-iors} for an overview).
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*
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* The implementation is based on the paper ``Microfacet Models
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* for Refraction through Rough Surfaces'' by Walter et al.
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* \cite{Walter07Microfacet}. It supports several different types of microfacet
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* distributions. Note that the choices are a bit more restricted here---in
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* comparison to other rough scattering models in Mitsuba,
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* the roughness cannot be textured, and anisotropic microfacet
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* distributions are not allowed.
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*
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* When no parameters are given, the plugin activates the default settings,
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* which describe a white polypropylene plastic material with a light amount
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* of roughness modeled using the Beckmann distribution.
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*
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* To get an intuition about the effect of the surface roughness
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* parameter $\alpha$, consider the following approximate differentiation:
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* a value of $\alpha=0.001-0.01$ corresponds to a material
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* with slight imperfections on an
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* otherwise smooth surface finish, $\alpha=0.1$ is relatively rough,
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* and $\alpha=0.3-0.7$ is \emph{extremely} rough (e.g. an etched or ground
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* finish). Values significantly above that are probably not too realistic.
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*
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* When rendering with the Phong microfacet
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* distributions, a conversion is used to turn the specified
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* $\alpha$ roughness value into the Phong exponent.
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* This is done in a way, such that the different
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* distributions all produce a similar appearance for
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* the same value of $\alpha$.\vspace{5mm}
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*
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* \begin{xml}[caption={A material definition for rough, black laquer.}, label=lst:roughplastic-lacquer]
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* <bsdf type="roughplastic">
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* <string name="distribution" value="beckmann"/>
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* <float name="alpha" value="0.05"/>
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* <float name="intIOR" value="1.61"/>
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* <spectrum name="diffuseReflectance" value="0"/>
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* </bsdf>
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* \end{xml}
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*
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*/
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class RoughPlastic : public BSDF {
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public:
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@ -76,7 +139,7 @@ public:
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props.getSpectrum("diffuseReflectance", Spectrum(0.5f)));
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/* Specifies the internal index of refraction at the interface */
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m_intIOR = lookupIOR(props, "intIOR", "bk7");
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m_intIOR = lookupIOR(props, "intIOR", "polypropylene");
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/* Specifies the external index of refraction at the interface */
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m_extIOR = lookupIOR(props, "extIOR", "air");
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@ -24,7 +24,17 @@ MTS_NAMESPACE_BEGIN
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/*! \plugin{twosided}{Two-sided BRDF adapter}
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*
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* Turns a nested one-sided BRDF onto a two-sided version that
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* By default, all non-transmissive scattering models in Mitsuba
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* are \emph{one-sided} --- in other words, they absorb all light
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* that is received on the backs-side or interior of any surfaces
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* associated with them. Holes in a mesh will thus be
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*
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* This is usually a good idea, since it will expose modeling
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* issues early on. But sometimes one is forced to deal with such
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* a bad mesh. In this case, this plugin that cannot be fixed.
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*
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*
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* This plugin turns a nested one-sided model onto a two-sided version that
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* can be used to render meshes where the back-side is visible.
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*
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* \begin{xml}
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@ -65,23 +75,22 @@ public:
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"a transmission component can be nested!");
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}
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Spectrum eval(const BSDFQueryRecord &bRec) const {
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Spectrum eval(const BSDFQueryRecord &bRec, EMeasure measure) const {
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BSDFQueryRecord b(bRec);
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if (Frame::cosTheta(b.wi) < 0) {
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b.wi.z *= -1;
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b.wo.z *= -1;
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}
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return m_nestedBRDF->eval(b);
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return m_nestedBRDF->eval(b, measure);
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}
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Float pdf(const BSDFQueryRecord &bRec) const {
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Float pdf(const BSDFQueryRecord &bRec, EMeasure measure) const {
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BSDFQueryRecord b(bRec);
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if (b.wi.z < 0) {
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b.wi.z *= -1;
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b.wo.z *= -1;
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}
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return m_nestedBRDF->pdf(b);
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return m_nestedBRDF->pdf(b, measure);
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}
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Spectrum sample(BSDFQueryRecord &bRec, const Point2 &sample) const {
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@ -112,7 +121,7 @@ public:
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if (flipped) {
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bRec.wi.z *= -1;
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if (!result.isZero() && pdf != 0)
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bRec.wo.z *= -1;
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}
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