325 lines
12 KiB
C++
325 lines
12 KiB
C++
/*
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This file is part of Mitsuba, a physically based rendering system.
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Copyright (c) 2007-2011 by Wenzel Jakob and others.
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Mitsuba is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License Version 3
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as published by the Free Software Foundation.
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Mitsuba is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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#include <mitsuba/render/scene.h>
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#include <mitsuba/hw/basicshader.h>
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MTS_NAMESPACE_BEGIN
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/*! \plugin{bump}{Bump map}
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*
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* \parameters{
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* \parameter{\Unnamed}{\Texture}{
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* The luminance of this texture specifies the amount of
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* displacement. The implementation ignores any constant
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* offset---only changes in the luminance matter.
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* }
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* \parameter{\Unnamed}{\BSDF}{A BSDF model that should
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* be affected by the bump map}
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* }
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* \renderings{
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* \rendering{Bump map based on tileable diagonal lines}{bsdf_bump_1}
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* \rendering{An irregular bump map}{bsdf_bump_2}
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* }
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*
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* Bump mapping \cite{Blinn1978Simulation} is a simple technique for cheaply
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* adding surface detail to a rendering. This is done by perturbing the
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* shading coordinate frame based on a displacement height field provided
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* as a texture. This method can lend objects a highly realistic and detailed
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* appearance (e.g. wrinkled or covered by scratches and other imperfections)
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* without requiring any changes to the input geometry.
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*
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* The implementation in Mitsuba uses the common approach of ignoring
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* the usually negligible texture-space derivative of the base mesh
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* surface normal. As side effect of this decision, it is invariant
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* to constant offsets in the height field texture---only variations in
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* its luminance cause changes to the shading frame.
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*
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* Note that the magnitude of the height field variations influences
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* the strength of the displacement. If desired, the \pluginref{scale}
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* texture plugin can be used to magnify or reduce the effect of a
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* bump map texture.
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* \begin{xml}[caption=A rough metal model with a scaled image-based bump map]
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* <bsdf type="bump">
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* <!-- The bump map is applied to a rough metal BRDF -->
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* <bsdf type="roughconductor"/>
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*
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* <texture type="scale">
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* <!-- The scale of the displacement gets multiplied by 10x -->
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* <float name="scale" value="10"/>
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*
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* <texture type="bitmap">
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* <string name="filename" value="bumpmap.png"/>
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* </texture>
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* </texture>
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* </bsdf>
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* \end{xml}
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*/
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class BumpMap : public BSDF {
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public:
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BumpMap(const Properties &props) : BSDF(props) { }
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BumpMap(Stream *stream, InstanceManager *manager)
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: BSDF(stream, manager) {
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m_nested = static_cast<BSDF *>(manager->getInstance(stream));
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m_displacement = static_cast<Texture *>(manager->getInstance(stream));
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configure();
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}
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void configure() {
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if (!m_nested)
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Log(EError, "A child BSDF instance is required");
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if (!m_displacement)
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Log(EError, "A displacement texture must be specified");
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m_components.clear();
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for (int i=0; i<m_nested->getComponentCount(); ++i)
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m_components.push_back(m_nested->getType(i) | ESpatiallyVarying | EAnisotropic);
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m_usesRayDifferentials = true;
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BSDF::configure();
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}
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void serialize(Stream *stream, InstanceManager *manager) const {
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BSDF::serialize(stream, manager);
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manager->serialize(stream, m_nested.get());
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manager->serialize(stream, m_displacement.get());
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}
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void addChild(const std::string &name, ConfigurableObject *child) {
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if (child->getClass()->derivesFrom(MTS_CLASS(BSDF))) {
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if (m_nested != NULL)
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Log(EError, "Only a single nested BSDF can be added!");
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m_nested = static_cast<BSDF *>(child);
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} else if (child->getClass()->derivesFrom(MTS_CLASS(Texture))) {
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if (m_displacement != NULL)
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Log(EError, "Only a single displacement texture can be specified!");
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m_displacement = static_cast<Texture *>(child);
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} else {
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BSDF::addChild(name, child);
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}
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}
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void perturbIntersection(const Intersection &its, Intersection &target) const {
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/* Determine the step size for the finite difference computation */
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Float du = 0.5f * std::abs(its.dudx) + std::abs(its.dudy),
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dv = 0.5f * std::abs(its.dvdx) + std::abs(its.dvdy);
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if (du == 0) du = Epsilon;
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if (dv == 0) dv = Epsilon;
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/* Compute the U and V displacementment derivatives */
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Float displacement, displacementU, displacementV;
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target = its;
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displacement = m_displacement->getValue(target).getLuminance();
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target.p = its.p + its.dpdu * du;
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target.uv = its.uv + Point2(du, 0);
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displacementU = m_displacement->getValue(target).getLuminance();
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target.p = its.p + its.dpdv * dv;
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target.uv = its.uv + Point2(0, dv);
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displacementV = m_displacement->getValue(target).getLuminance();
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target.p = its.p;
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target.uv = its.uv;
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Float dDisplaceDu = (displacementU - displacement) / du;
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Float dDisplaceDv = (displacementV - displacement) / dv;
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/* Build a perturbed frame -- ignores the usually
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negligible normal derivative term */
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Vector dpdu = its.dpdu + its.shFrame.n * (
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dDisplaceDu - dot(its.shFrame.n, its.dpdu));
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Vector dpdv = its.dpdv + its.shFrame.n * (
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dDisplaceDv - dot(its.shFrame.n, its.dpdv));
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dpdu = normalize(dpdu);
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dpdv = normalize(dpdv - dpdu * dot(dpdv, dpdu));
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target.shFrame.s = dpdu;
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target.shFrame.t = dpdv;
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target.shFrame = Frame(Normal(cross(dpdv, dpdu)));
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if (dot(target.shFrame.n, target.geoFrame.n) < 0)
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target.shFrame.n *= -1;
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}
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Spectrum eval(const BSDFQueryRecord &bRec, EMeasure measure) const {
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const Intersection& its = bRec.its;
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Intersection perturbed;
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perturbIntersection(its, perturbed);
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BSDFQueryRecord perturbedQuery(perturbed,
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perturbed.toLocal(its.toWorld(bRec.wi)),
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perturbed.toLocal(its.toWorld(bRec.wo)), bRec.quantity);
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if (Frame::cosTheta(bRec.wo) * Frame::cosTheta(perturbedQuery.wo) <= 0)
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return Spectrum(0.0f);
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perturbedQuery.sampler = bRec.sampler;
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perturbedQuery.typeMask = bRec.typeMask;
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perturbedQuery.component = bRec.component;
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return m_nested->eval(perturbedQuery, measure);
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}
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Float pdf(const BSDFQueryRecord &bRec, EMeasure measure) const {
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const Intersection& its = bRec.its;
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Intersection perturbed;
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perturbIntersection(its, perturbed);
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BSDFQueryRecord perturbedQuery(perturbed,
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perturbed.toLocal(its.toWorld(bRec.wi)),
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perturbed.toLocal(its.toWorld(bRec.wo)), bRec.quantity);
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if (Frame::cosTheta(bRec.wo) * Frame::cosTheta(perturbedQuery.wo) <= 0)
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return 0;
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perturbedQuery.quantity = bRec.quantity;
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perturbedQuery.sampler = bRec.sampler;
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perturbedQuery.typeMask = bRec.typeMask;
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perturbedQuery.component = bRec.component;
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return m_nested->pdf(perturbedQuery, measure);
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}
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Spectrum sample(BSDFQueryRecord &bRec, Float &pdf, const Point2 &sample) const {
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const Intersection& its = bRec.its;
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Intersection perturbed;
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perturbIntersection(its, perturbed);
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BSDFQueryRecord perturbedQuery(perturbed, bRec.sampler, bRec.quantity);
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perturbedQuery.wi = perturbed.toLocal(its.toWorld(bRec.wi));
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perturbedQuery.typeMask = bRec.typeMask;
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perturbedQuery.component = bRec.component;
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Spectrum result = m_nested->sample(perturbedQuery, pdf, sample);
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if (!result.isZero()) {
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bRec.sampledComponent = perturbedQuery.sampledComponent;
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bRec.sampledType = perturbedQuery.sampledType;
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bRec.wo = its.toLocal(perturbed.toWorld(perturbedQuery.wo));
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if (Frame::cosTheta(bRec.wo) * Frame::cosTheta(perturbedQuery.wo) <= 0)
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return Spectrum(0.0f);
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}
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return result;
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}
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Spectrum sample(BSDFQueryRecord &bRec, const Point2 &sample) const {
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const Intersection& its = bRec.its;
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Intersection perturbed;
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perturbIntersection(its, perturbed);
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BSDFQueryRecord perturbedQuery(perturbed, bRec.sampler, bRec.quantity);
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perturbedQuery.wi = perturbed.toLocal(its.toWorld(bRec.wi));
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perturbedQuery.sampler = bRec.sampler;
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perturbedQuery.typeMask = bRec.typeMask;
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perturbedQuery.component = bRec.component;
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Spectrum result = m_nested->sample(perturbedQuery, sample);
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if (!result.isZero()) {
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bRec.sampledComponent = perturbedQuery.sampledComponent;
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bRec.sampledType = perturbedQuery.sampledType;
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bRec.wo = its.toLocal(perturbed.toWorld(perturbedQuery.wo));
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if (Frame::cosTheta(bRec.wo) * Frame::cosTheta(perturbedQuery.wo) <= 0)
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return Spectrum(0.0f);
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}
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return result;
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}
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Shader *createShader(Renderer *renderer) const;
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std::string toString() const {
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std::ostringstream oss;
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oss << "BumpMap[" << endl
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<< " name = \"" << getName() << "\"," << endl
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<< " displacement = " << indent(m_displacement->toString()) << endl
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<< " nested = " << indent(m_nested->toString()) << endl
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<< "]";
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return oss.str();
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}
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MTS_DECLARE_CLASS()
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protected:
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ref<Texture> m_displacement;
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ref<BSDF> m_nested;
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};
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// ================ Hardware shader implementation ================
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/**
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* This is a quite approximate version of the bump map model -- it likely
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* won't match the reference exactly, but it should be good enough for
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* preview purposes
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*/
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class BumpMapShader : public Shader {
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public:
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BumpMapShader(Renderer *renderer, const BSDF *nested, const Texture *displacement)
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: Shader(renderer, EBSDFShader), m_nested(nested), m_displacement(displacement) {
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m_nestedShader = renderer->registerShaderForResource(m_nested.get());
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m_displacementShader = renderer->registerShaderForResource(m_displacement.get());
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}
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bool isComplete() const {
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return m_nestedShader.get() != NULL;
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}
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void cleanup(Renderer *renderer) {
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renderer->unregisterShaderForResource(m_nested.get());
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renderer->unregisterShaderForResource(m_displacement.get());
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}
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void putDependencies(std::vector<Shader *> &deps) {
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deps.push_back(m_nestedShader.get());
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deps.push_back(m_displacementShader.get());
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}
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void generateCode(std::ostringstream &oss,
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const std::string &evalName,
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const std::vector<std::string> &depNames) const {
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oss << "vec3 " << evalName << "(vec2 uv, vec3 wi, vec3 wo) {" << endl
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<< " float du = abs(dFdx(uv.x)), dv = abs(dFdx(uv.y));" << endl
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<< " if (du == 0.0) du = 0.001;" << endl
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<< " if (dv == 0.0) dv = 0.001;" << endl
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<< " float displacement = " << depNames[1] << "(uv)[0];" << endl
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<< " float displacementU = " << depNames[1] << "(uv + vec2(du, 0.0))[0];" << endl
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<< " float displacementV = " << depNames[1] << "(uv + vec2(0.0, dv))[0];" << endl
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<< " float dfdu = (displacementU - displacement)/du;" << endl
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<< " float dfdv = (displacementV - displacement)/dv;" << endl
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<< " vec3 dpdu = normalize(vec3(1.0, 0.0, dfdu));" << endl
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<< " vec3 dpdv = vec3(0.0, 1.0, dfdv);" << endl
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<< " dpdv = normalize(dpdv - dot(dpdu, dpdv)*dpdu);" << endl
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<< " vec3 n = cross(dpdu, dpdv);" << endl
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<< " wi = vec3(dot(wi, dpdu), dot(wi, dpdv), dot(wi, n));" << endl
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<< " wo = vec3(dot(wo, dpdu), dot(wo, dpdv), dot(wo, n));" << endl
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<< " return " << depNames[0] << "(uv, wi, wo);" << endl
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<< "}" << endl
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<< endl
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<< "vec3 " << evalName << "_diffuse(vec2 uv, vec3 wi, vec3 wo) {" << endl
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<< " return " << depNames[0] << "_diffuse(uv, wi, wo);" << endl
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<< "}" << endl;
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}
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MTS_DECLARE_CLASS()
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private:
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ref<const BSDF> m_nested;
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ref<const Texture> m_displacement;
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ref<Shader> m_nestedShader;
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ref<Shader> m_displacementShader;
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};
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Shader *BumpMap::createShader(Renderer *renderer) const {
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return new BumpMapShader(renderer, m_nested.get(), m_displacement.get());
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}
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MTS_IMPLEMENT_CLASS(BumpMapShader, false, Shader)
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MTS_IMPLEMENT_CLASS_S(BumpMap, false, BSDF)
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MTS_EXPORT_PLUGIN(BumpMap, "Smooth dielectric coating");
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MTS_NAMESPACE_END
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