improvements to the dielectric material

data/tests/test_bsdf.xml

@@ -2,6 +2,12 @@
 	 to be tested for consistency. This is done
 	 using the testcase 'test_chisquare' -->
 <scene>
+	<!-- Test the dielectric model -->
+	<bsdf type="dielectric">
+		<string name="intIOR" value="water"/>
+		<string name="extIOR" value="air"/>
+	</bsdf>
+
 	<!-- Test the diffuse model -->
 	<bsdf type="diffuse"/>
 

doc/macros.sty

@@ -40,6 +40,7 @@
 	\end{tabular}}
 	\end{figure}
 	\setlength\fboxrule\fboxrulebackup
+	\arrayrulecolor{black}
 	}
 	
 \newcommand{\renderings}[1]{

src/bsdfs/SConscript

@@ -13,6 +13,8 @@ Import('env', 'plugins')
 #plugins += env.SharedLibrary('roughdiffuse', ['roughdiffuse.cpp'])
 
 
+plugins += env.SharedLibrary('dielectric', ['dielectric.cpp'])
+
 # Diffuse models
 plugins += env.SharedLibrary('difftrans', ['difftrans.cpp'])
 plugins += env.SharedLibrary('diffuse', ['diffuse.cpp'])
@@ -21,7 +23,6 @@ plugins += env.SharedLibrary('diffuse', ['diffuse.cpp'])
 plugins += env.SharedLibrary('mixture', ['mixture.cpp'])
 
 #plugins += env.SharedLibrary('twosided', ['twosided.cpp'])
-#plugins += env.SharedLibrary('dielectric', ['dielectric.cpp'])
 
 #plugins += env.SharedLibrary('difftrans', ['difftrans.cpp'])
 #plugins += env.SharedLibrary('mask', ['mask.cpp'])

src/bsdfs/dielectric.cpp

@@ -18,14 +18,17 @@
 
 #include <mitsuba/render/bsdf.h>
 #include <mitsuba/render/consttexture.h>
+#include "ior.h"
 
 MTS_NAMESPACE_BEGIN
 
 /*! \plugin{dielectric}{Smooth dielectric material}
  *
  * \parameters{
- *     \parameter{intIOR}{\Float}{Interior index of refraction \default{1.5046}}
+ *     \parameter{intIOR}{\Float\Or\String}{Interior index of refraction specified
- *     \parameter{extIOR}{\Float}{Exterior index of refraction \default{1.0}}
+ *      numerically or using a known material name. \default{\texttt{bk7} / 1.5046}}
+ *     \parameter{extIOR}{\Float\Or\String}{Exterior index of refraction specified
+ *      numerically or using a known material name. \default{\texttt{air} / 1.000277}}
  *     \parameter{specular\showbreak Reflectance}{\Spectrum\Or\Texture}{Optional
  *         factor used to modulate the reflectance component\default{1.0}}
  *     \lastparameter{specular\showbreak Transmittance}{\Spectrum\Or\Texture}{Optional
@@ -49,14 +52,14 @@ MTS_NAMESPACE_BEGIN
  * In this model, the microscopic surface structure of the surface is assumed to be perfectly 
  * smooth, resulting in a degenerate\footnote{Meaning that for any given incoming ray of light,
  * the model always scatters into a discrete set of directions, as opposed to a continuum.} 
- * BSDF described by a Dirac delta function. For a similar model that describes a rough 
+ * BSDF described by a Dirac delta function. For a similar model that instead describes a 
- * surface microstructure, take a look at the \pluginref{roughdielectric} plugin. 
+ * rough surface microstructure, take a look at the \pluginref{roughdielectric} plugin. 
  *
  * \begin{xml}[caption=A simple air-to-water interface, label=lst:dielectric-water]
  * <shape type="...">
  *     <bsdf type="dielectric">
- *         <float name="intIOR" value="1.33"/>
+ *         <string name="intIOR" value="water"/>
- *         <float name="extIOR" value="1.0"/>
+ *         <string name="extIOR" value="air"/>
  *     </bsdf>
  * <shape>
  * \end{xml}
@@ -68,29 +71,74 @@ MTS_NAMESPACE_BEGIN
  * In many cases, we will want to additionally describe the \emph{medium} within a
  * dielectric material. This requires the use of a rendering technique that is
  * aware of media (e.g. the volumetric path tracer). An example of how one might
- * describe a slightly absorbing piece of glass is given below:
+ * describe a slightly absorbing piece of glass is given on the next page:
- *
+ * \newpage
- * \begin{xml}[caption=A glass material with absorption, label=lst:dielectric-glass]
+ * \begin{xml}[caption=A glass material with absorption (based on the 
+ *    Beer-Lambert law). This material can only be used by an integrator
+ *    that is aware of participating media., label=lst:dielectric-glass]
  * <shape type="...">
  *     <bsdf type="dielectric">
  *         <float name="intIOR" value="1.504"/>
  *         <float name="extIOR" value="1.0"/>
  *     </bsdf>
+ *
  *     <medium type="homogeneous" name="interior">
  *			<rgb name="sigmaS" value="0, 0, 0"/>
  *			<rgb name="sigmaA" value="4, 4, 2"/>
  *     </medium>
  * <shape>
  * \end{xml}
+ * \vspace{1cm}
+ *
+ * \begin{table}[h!]
+ *     \centering
+ *     \begin{tabular}{>{\ttfamily}p{5cm}r@{.}lp{.8cm}>{\ttfamily}p{5cm}r@{.}l}
+ *         \toprule
+ *         \rmfamily Name & \multicolumn{2}{l}{Value}& &
+ *         \rmfamily Name & \multicolumn{2}{l}{Value}\\
+ *         \cmidrule{1-3} \cmidrule{5-7}
+ *         vacuum               & 1 & 0 &  &
+ *         silicone oil         & 1 & 52045\\
+ *         helium               & 1 & 00004 & &
+ *         bromine              & 1 & 661\\
+ *         hydrogen             & 1 & 00013& &
+ *         water ice            & 1 & 31\\[-.8mm]
+ *         \cmidrule{5-7}\\[-5.5mm]
+ *         air                  & 1 & 00028& &
+ *         fused quartz         & 1 & 458\\
+ *         carbon dioxide       & 1 & 00045& &
+ *         pyrex                & 1 & 470\\[-.8mm]
+ *         \cmidrule{1-3}\\[-5.5mm]
+ *         water                & 1 & 3330& &
+ *         acrylic glass        & 1 & 490\\
+ *         acetone              & 1 & 36 & &
+ *         bk7                  & 1 & 5046\\
+ *         ethanol              & 1 & 361& &
+ *         sodium chloride      & 1 & 544\\
+ *         carbon tetrachloride & 1 & 461& &
+ *         amber                & 1 & 55\\
+ *         glycerol             & 1 & 4729& &
+ *         pet                  & 1 & 575\\
+ *         benzene              & 1 & 501& &
+ *         diamond              & 2 & 419\\
+ *         \bottomrule
+ *     \end{tabular}
+ *     \caption{
+ *         \label{tbl:dielectric-iors}
+ *          This table lists all supported material names that can be passed
+ *          into the \pluginref{dielectric} plugin, along with the associated 
+ *          index of refraction at standard conditions.
+ *     }
+ * \end{table}
  */
 class SmoothDielectric : public BSDF {
 public:
-	SmoothDielectric(const Properties &props) 
+	SmoothDielectric(const Properties &props) : BSDF(props) {
-			: BSDF(props) {
 		/* Specifies the internal index of refraction at the interface */
-		m_intIOR = props.getFloat("intIOR", 1.5046f);
+		m_intIOR = lookupIOR(props, "intIOR", "bk7");
+
 		/* Specifies the external index of refraction at the interface */
-		m_extIOR = props.getFloat("extIOR", 1);
+		m_extIOR = lookupIOR(props, "extIOR", "air");
 
 		m_specularReflectance = new ConstantSpectrumTexture(
 			props.getSpectrum("specularReflectance", Spectrum(1.0f)));
@@ -199,7 +247,7 @@ public:
 			} else {
 				bRec.sampledComponent = 1;
 				bRec.sampledType = EDeltaTransmission;
-;
+
 				/* Given cos(N, transmittedRay), compute the 
 				   transmitted direction */
 				bRec.wo = refract(bRec.wi, eta, cosThetaT);
@@ -230,15 +278,15 @@ public:
 		}
 	}
 
-	Spectrum eval(const BSDFQueryRecord &bRec) const {
+	Spectrum eval(const BSDFQueryRecord &bRec, EMeasure measure) const {
 		bool sampleReflection   = (bRec.typeMask & EDeltaReflection)
 				&& (bRec.component == -1 || bRec.component == 0);
 		bool sampleTransmission = (bRec.typeMask & EDeltaTransmission)
 				&& (bRec.component == -1 || bRec.component == 1);
-		bool reflection = BSDF::cosTheta(bRec.wo) * BSDF::cosTheta(bRec.wi) > 0;
+		bool reflection = Frame::cosTheta(bRec.wo) * Frame::cosTheta(bRec.wi) > 0;
 		
 		if ((reflection && !sampleReflection) || 
-		   (!reflection && !sampleTransmission))
+		   (!reflection && !sampleTransmission) || measure != EDiscrete)
 			return Spectrum(0.0f);
 
 		Float fr = fresnel(Frame::cosTheta(bRec.wi), m_extIOR, m_intIOR);
@@ -263,18 +311,18 @@ public:
 				&& (bRec.component == -1 || bRec.component == 0);
 		bool sampleTransmission = (bRec.typeMask & EDeltaTransmission)
 				&& (bRec.component == -1 || bRec.component == 1);
-
+		bool reflection = Frame::cosTheta(bRec.wo)
-		if (measure != EDiscrete || (!sampleReflection && !sampleTransmission))
-			return 0.0f;
-
-		bool reflection = Frame::costheta(bRec.wo)
 			* Frame::cosTheta(bRec.wi) > 0;
 
+		if ((reflection && !sampleReflection) || 
+		   (!reflection && !sampleTransmission) || measure != EDiscrete)
+			return 0.0f;
+
 		if (sampleTransmission && sampleReflection) {
 			Float Fr = fresnel(Frame::cosTheta(bRec.wi), m_extIOR, m_intIOR);
 			return reflection ? Fr : (1 - Fr);
 		} else {
-			return sampleReflection == reflection ? 1.0f : 0.0f;
+			return 1.0f;
 		}
 	}
 

src/bsdfs/ior.h

@@ -0,0 +1,103 @@
+/*
+    This file is part of Mitsuba, a physically based rendering system.
+
+    Copyright (c) 2007-2011 by Wenzel Jakob and others.
+
+    Mitsuba is free software; you can redistribute it and/or modify
+    it under the terms of the GNU General Public License Version 3
+    as published by the Free Software Foundation.
+
+    Mitsuba is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program. If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#if !defined(__IOR_DATA_H)
+#define __IOR_DATA_H
+
+#include <mitsuba/mitsuba.h>
+#include <boost/algorithm/string.hpp>
+
+MTS_NAMESPACE_BEGIN
+
+struct IOREntry {
+	const char *name;
+	Float value;
+};
+
+/**
+ * Many values are taken from Hecht, Optics, 
+ * Fourth Edition.
+ * 
+ * The IOR values are from measurements between
+ * 0 and 20 degrees celsius at ~589 nm.
+ */
+static IOREntry iorData[] = {
+	{ "vacuum",                1.0f      },
+	{ "helium",                1.000036f },
+	{ "hydrogen",              1.000132f },
+	{ "air",                   1.000277f },
+	{ "carbon dioxide",        1.00045f  },
+	//////////////////////////////////////
+	{ "water",                 1.3330f   },
+	{ "acetone",               1.36f     },
+	{ "ethanol",               1.361f    },
+	{ "carbon tetrachloride",  1.461f    },
+	{ "glycerol",              1.4729f   },
+	{ "benzene",               1.501f    },
+	{ "silicone oil",          1.52045f  },
+	{ "bromine",               1.661f    },
+	//////////////////////////////////////
+	{ "water ice",             1.31f     },
+	{ "fused quartz",          1.458f    },
+	{ "pyrex",                 1.470f    },
+	{ "acrylic glass",         1.490f    },
+	{ "bk7",                   1.5046f   },
+	{ "sodium chloride",       1.544f    },
+	{ "amber",                 1.55f     },
+	{ "pet",                   1.5750f   },
+	{ "diamond",               2.419f    },
+
+	{ NULL,                    0.0f      }
+};
+
+static Float lookupIOR(const std::string &name) {
+	std::string lowerCase = boost::to_lower_copy(name);
+	IOREntry *ior = iorData;
+
+	while (ior->name) {
+		if (lowerCase == ior->name)
+			return ior->value;
+		++ior;
+	}
+
+	std::ostringstream oss;
+	oss << "Unable to find an IOR value for \"" << lowerCase 
+		<< "\"! Valid choices are:";
+
+	/* Unable to find the IOR value by name -- print an error
+	   message that lists all possible options */
+	for (ior = iorData; ior->name != NULL; ++ior) {
+		oss << ior->name;
+		if ((ior+1)->name)
+			oss << ", ";
+	}
+
+	SLog(EError, "%s", oss.str().c_str());
+	return 0.0f;
+}
+
+static Float lookupIOR(const Properties &props, const std::string &paramName, const std::string &defaultValue) {
+	if (props.hasProperty(paramName) && props.getType(paramName) == Properties::EFloat)
+		return props.getFloat(paramName);
+	else
+		return lookupIOR(props.getString(paramName, defaultValue));
+}
+
+MTS_NAMESPACE_END
+
+#endif /* __IOR_DATA_H */