mut_manifold.h

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/*
    This file is part of Mitsuba, a physically based rendering system.

    Copyright (c) 2007-2014 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/>.
*/

#pragma once
#if !defined(__MITSUBA_BIDIR_MUT_MANIFOLD_H_)
#define __MITSUBA_BIDIR_MUT_MANIFOLD_H_

#include <mitsuba/bidir/mutator.h>

MTS_NAMESPACE_BEGIN

#define MTS_MANIFOLD_QUANTILE_SURFACE 0.9f
#define MTS_MANIFOLD_QUANTILE_MEDIUM  0.5f

/**
 * \brief Specular manifold perturbation strategy
 *
 * \author Wenzel Jakob
 * \ingroup libbidir
 */
class MTS_EXPORT_BIDIR ManifoldPerturbation : public MutatorBase {
public:
        /**
         * \brief Construct a new specular manifold perturbation strategy
         *
         * \param scene
         *     A pointer to the underlying scene
         *
         * \param sampler
         *     A sample generator
         *
         * \param pool
         *     A memory pool used to allocate new path vertices and edges
         */
        ManifoldPerturbation(const Scene *scene, Sampler *sampler,
                MemoryPool &pool,
                Float probFactor,
                bool enableOffsetManifolds,
                bool enableSpecularMedia,
                Float avgAngleChangeSurface = 0,
                Float avgAngleChangeMedium = 0);

        // =============================================================
        //! @{ \name Implementation of the Mutator interface

        EMutationType getType() const;
        Float suitability(const Path &path) const;
        bool sampleMutation(Path &source, Path &proposal,
                        MutationRecord &muRec, const MutationRecord& sourceMuRec);
        Float Q(const Path &source, const Path &proposal,
                        const MutationRecord &muRec) const;
        void accept(const MutationRecord &muRec);

        //! @}
        // =============================================================

        MTS_DECLARE_CLASS()
protected:
        /// Virtual destructor
        virtual ~ManifoldPerturbation();

        /// Helper function for choosing mutation strategies
        bool sampleMutationRecord(const Path &source,
                int &a, int &b, int &c, int &step);

        Float nonspecularProbSurface(Float alpha) const;
        Float nonspecularProbMedium(Float g) const;

        Float nonspecularProb(const PathVertex *vertex) const;
        inline Float specularProb(const PathVertex *vertex) const {
                return 1 - nonspecularProb(vertex);
        }

        int getSpecularChainEnd(const Path &path, int pos, int step);
protected:
        ref<const Scene> m_scene;
        ref<Sampler> m_sampler;
        mutable ref<SpecularManifold> m_manifold;
        MemoryPool &m_pool;
        Float m_probFactor, m_probFactor2;
        bool m_enableOffsetManifolds;
        bool m_enableSpecularMedia;
        static Float m_thetaDiffSurface;
        static Float m_thetaDiffMedium;
        static int m_thetaDiffSurfaceSamples;
        static int m_thetaDiffMediumSamples;
        static Mutex *m_thetaDiffMutex;
};

MTS_NAMESPACE_END

#endif /*__MITSUBA_BIDIR_MUT_MANIFOLD_H_ */