228 lines
7.1 KiB
C++
228 lines
7.1 KiB
C++
/*
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This file is part of Mitsuba, a physically based rendering system.
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Copyright (c) 2007-2014 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/core/statistics.h>
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#include <mitsuba/bidir/mut_caustic.h>
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MTS_NAMESPACE_BEGIN
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static StatsCounter statsAccepted("Caustic perturbation",
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"Acceptance rate", EPercentage);
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static StatsCounter statsGenerated("Caustic perturbation",
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"Successful generation rate", EPercentage);
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CausticPerturbation::CausticPerturbation(const Scene *scene, Sampler *sampler,
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MemoryPool &pool, Float minJump, Float coveredArea) :
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m_scene(scene), m_sampler(sampler), m_pool(pool) {
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if (!scene->getSensor()->getClass()->derivesFrom(MTS_CLASS(PerspectiveCamera)))
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Log(EError, "The caustic perturbation requires a perspective camera.");
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const PerspectiveCamera *camera = static_cast<const PerspectiveCamera *>(scene->getSensor());
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Vector2i filmSize = camera->getFilm()->getSize(),
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cropSize = camera->getFilm()->getCropSize();
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/* Simple heuristic for choosing a jump size: assumes that each
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pixel on the camera subtends the same area on the sphere */
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Float degPerPixel = std::min(
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camera->getXFov() / filmSize.x,
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camera->getYFov() / filmSize.y),
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radPerPixel = degPerPixel * M_PI / 180.0f;
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Float r1 = minJump,
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r2 = std::sqrt(coveredArea * cropSize.x*cropSize.y / M_PI); /* [Veach, p. 354] */
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/* These represent the *desired* angle change range as seen from the camera */
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m_theta1 = radPerPixel * r1;
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m_theta2 = radPerPixel * r2;
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m_logRatio = -math::fastlog(m_theta2 / m_theta1);
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}
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CausticPerturbation::~CausticPerturbation() { }
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Mutator::EMutationType CausticPerturbation::getType() const {
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return ECausticPerturbation;
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}
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Float CausticPerturbation::suitability(const Path &path) const {
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int k = path.length(), m = k - 1, l = m - 1;
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if (k < 4 || !path.vertex(l)->isConnectable())
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return false;
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--l;
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while (l >= 0 && !path.vertex(l)->isConnectable())
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--l;
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return l >= 1 ? 1.0f : 0.0f;
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}
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bool CausticPerturbation::sampleMutation(
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Path &source, Path &proposal, MutationRecord &muRec, const MutationRecord& sourceMuRec) {
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int k = source.length(), m = k - 1, l = m - 1;
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if (k < 4 || !source.vertex(l)->isConnectable())
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return false;
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--l;
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while (l >= 0 && !source.vertex(l)->isConnectable())
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--l;
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if (l < 1)
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return false;
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muRec = MutationRecord(ECausticPerturbation, l, m, m-l,
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source.getPrefixSuffixWeight(l, m));
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statsAccepted.incrementBase();
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statsGenerated.incrementBase();
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/* Heuristic perturbation size computation (Veach, p.354) */
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Float lengthE = source.edge(m-1)->length;
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Float lengthL = 0;
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for (int i=l; i<m-1; ++i)
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lengthL += source.edge(i)->length;
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Float factor = lengthE/lengthL,
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theta1 = m_theta1 * factor,
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theta2 = m_theta2 * factor;
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Vector woSource = normalize(source.vertex(l+1)->getPosition()
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- source.vertex(l)->getPosition());
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Float phi = m_sampler->next1D() * 2 * M_PI;
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Float theta = theta2 * math::fastexp(m_logRatio * m_sampler->next1D());
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Vector wo = Frame(woSource).toWorld(sphericalDirection(theta, phi));
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/* Allocate memory for the proposed path */
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proposal.clear();
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proposal.append(source, 0, l+1);
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proposal.append(m_pool.allocEdge());
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for (int i=l+1; i<m; ++i) {
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proposal.append(m_pool.allocVertex());
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proposal.append(m_pool.allocEdge());
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}
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proposal.append(source, m, k+1);
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proposal.vertex(l) = proposal.vertex(l)->clone(m_pool);
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proposal.vertex(m) = proposal.vertex(m)->clone(m_pool);
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BDAssert(proposal.vertexCount() == source.vertexCount());
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BDAssert(proposal.edgeCount() == source.edgeCount());
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Float dist = source.edge(l)->length +
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perturbMediumDistance(m_sampler, source.vertex(l+1));
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/* Sample a perturbation and propagate it through specular interactions */
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if (!proposal.vertex(l)->perturbDirection(m_scene,
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proposal.vertex(l-1), proposal.edge(l-1),
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proposal.edge(l), proposal.vertex(l+1), wo, dist,
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source.vertex(l+1)->getType(), EImportance)) {
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proposal.release(l, m+1, m_pool);
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return false;
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}
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Vector woProposal = normalize(proposal.vertex(l+1)->getPosition()
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- source.vertex(l)->getPosition());
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theta = unitAngle(woSource, woProposal);
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if (theta >= theta2 || theta <= theta1) {
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proposal.release(l, m+1, m_pool);
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return false;
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}
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/* If necessary, propagate the perturbation through a sequence of
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ideally specular interactions */
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for (int i=l+1; i<m-1; ++i) {
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Float dist = source.edge(i)->length +
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perturbMediumDistance(m_sampler, source.vertex(i+1));
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if (!proposal.vertex(i)->propagatePerturbation(m_scene,
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proposal.vertex(i-1), proposal.edge(i-1),
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proposal.edge(i), proposal.vertex(i+1),
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source.vertex(i)->getComponentType(), dist,
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source.vertex(i+1)->getType(), EImportance)) {
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proposal.release(l, m+1, m_pool);
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return false;
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}
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}
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if (!PathVertex::connect(m_scene,
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proposal.vertex(m-2),
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proposal.edge(m-2),
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proposal.vertex(m-1),
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proposal.edge(m-1),
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proposal.vertex(m),
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proposal.edge(m),
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proposal.vertex(m+1))) {
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proposal.release(l, m+1, m_pool);
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return false;
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}
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proposal.vertex(k-1)->updateSamplePosition(
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proposal.vertex(k-2));
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++statsGenerated;
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return true;
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}
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Float CausticPerturbation::Q(const Path &source, const Path &proposal,
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const MutationRecord &muRec) const {
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int m = muRec.m, l = muRec.l;
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/* Heuristic perturbation size computation (Veach, p.354) */
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Float lengthE = source.edge(m-1)->length;
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Float lengthL = 0;
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for (int i=l; i<m-1; ++i)
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lengthL += source.edge(i)->length;
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Float factor = lengthE/lengthL,
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theta1 = m_theta1 * factor,
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theta2 = m_theta2 * factor;
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Vector d1 = normalize(source.vertex(l+1)->getPosition() - source.vertex(l)->getPosition());
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Vector d2 = normalize(proposal.vertex(l+1)->getPosition() - source.vertex(l)->getPosition());
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Float theta = unitAngle(d1, d2);
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if (theta >= theta2 || theta <= theta1)
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return 0.0f;
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Float solidAngleDensity = 1.0f / (2*M_PI * -m_logRatio * std::sin(theta) * theta);
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Spectrum weight = muRec.weight * proposal.edge(m-1)->evalCached(
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proposal.vertex(m-1), proposal.vertex(m), PathEdge::EEverything);
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for (int i=l; i<m-1; ++i) {
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const PathVertex *v0 = proposal.vertex(i),
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*v1 = proposal.vertex(i+1);
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const PathEdge *edge = proposal.edge(i);
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weight *= edge->evalCached(v0, v1,
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PathEdge::ETransmittance | PathEdge::EValueCosineImp);
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if (v1->isMediumInteraction())
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weight /= pdfMediumPerturbation(source.vertex(i+1),
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source.edge(i), edge);
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}
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const Float lumWeight = weight.getLuminance();
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if(lumWeight <= RCPOVERFLOW)
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return 0.f;
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return solidAngleDensity / lumWeight;
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}
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void CausticPerturbation::accept(const MutationRecord &) {
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++statsAccepted;
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}
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MTS_IMPLEMENT_CLASS(CausticPerturbation, false, Mutator)
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MTS_NAMESPACE_END
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