SPHSolver2.hpp

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// This code is based on Jet framework.
// Copyright (c) 2018 Doyub Kim
// CubbyFlow is voxel-based fluid simulation engine for computer games.
// Copyright (c) 2020 CubbyFlow Team
// Core Part: Chris Ohk, Junwoo Hwang, Jihong Sin, Seungwoo Yoo
// AI Part: Dongheon Cho, Minseo Kim
// We are making my contributions/submissions to this project solely in our
// personal capacity and are not conveying any rights to any intellectual
// property of any third parties.

#ifndef CUBBYFLOW_SPH_SOLVER2_HPP
#define CUBBYFLOW_SPH_SOLVER2_HPP

#include <Core/Particle/SPHSystemData.hpp>
#include <Core/Solver/Particle/ParticleSystemSolver2.hpp>

namespace CubbyFlow
{
class SPHSolver2 : public ParticleSystemSolver2
{
 public:
    class Builder;

    SPHSolver2();

    SPHSolver2(double targetDensity, double targetSpacing,
               double relativeKernelRadius);

    SPHSolver2(const SPHSolver2&) = delete;

    SPHSolver2(SPHSolver2&&) noexcept = delete;

    ~SPHSolver2() override = default;

    SPHSolver2& operator=(const SPHSolver2&) = delete;

    SPHSolver2& operator=(SPHSolver2&&) noexcept = delete;

    [[nodiscard]] double GetEosExponent() const;

    void SetEosExponent(double newEosExponent);

    [[nodiscard]] double GetNegativePressureScale() const;

    void SetNegativePressureScale(double newNegativePressureScale);

    [[nodiscard]] double GetViscosityCoefficient() const;

    void SetViscosityCoefficient(double newViscosityCoefficient);

    [[nodiscard]] double GetPseudoViscosityCoefficient() const;

    void SetPseudoViscosityCoefficient(double newPseudoViscosityCoefficient);

    [[nodiscard]] double GetSpeedOfSound() const;

    void SetSpeedOfSound(double newSpeedOfSound);

    [[nodiscard]] double GetTimeStepLimitScale() const;

    void SetTimeStepLimitScale(double newScale);

    [[nodiscard]] SPHSystemData2Ptr GetSPHSystemData() const;

    [[nodiscard]] static Builder GetBuilder();

 protected:
    [[nodiscard]] unsigned int GetNumberOfSubTimeSteps(
        double timeIntervalInSeconds) const override;

    void AccumulateForces(double timeStepInSeconds) override;

    void OnBeginAdvanceTimeStep(double timeStepInSeconds) override;

    void OnEndAdvanceTimeStep(double timeStepInSeconds) override;

    virtual void AccumulateNonPressureForces(double timeStepInSeconds);

    virtual void AccumulatePressureForce(double timeStepInSeconds);

    void ComputePressure();

    void AccumulatePressureForce(const ConstArrayView1<Vector2D>& positions,
                                 const ConstArrayView1<double>& densities,
                                 const ConstArrayView1<double>& pressures,
                                 ArrayView1<Vector2D> pressureForces);

    void AccumulateViscosityForce();

    void ComputePseudoViscosity(double timeStepInSeconds);

 private:
    double m_eosExponent = 7.0;

    double m_negativePressureScale = 0.0;

    double m_viscosityCoefficient = 0.01;

    double m_pseudoViscosityCoefficient = 10.0;

    double m_speedOfSound = 100.0;

    double m_timeStepLimitScale = 1.0;
};

using SPHSolver2Ptr = std::shared_ptr<SPHSolver2>;

template <typename DerivedBuilder>
class SPHSolverBuilderBase2
{
 public:
    [[nodiscard]] DerivedBuilder& WithTargetDensity(double targetDensity);

    [[nodiscard]] DerivedBuilder& WithTargetSpacing(double targetSpacing);

    [[nodiscard]] DerivedBuilder& WithRelativeKernelRadius(
        double relativeKernelRadius);

 protected:
    double m_targetDensity = WATER_DENSITY;
    double m_targetSpacing = 0.1;
    double m_relativeKernelRadius = 1.8;
};

template <typename T>
T& SPHSolverBuilderBase2<T>::WithTargetDensity(double targetDensity)
{
    m_targetDensity = targetDensity;
    return static_cast<T&>(*this);
}

template <typename T>
T& SPHSolverBuilderBase2<T>::WithTargetSpacing(double targetSpacing)
{
    m_targetSpacing = targetSpacing;
    return static_cast<T&>(*this);
}

template <typename T>
T& SPHSolverBuilderBase2<T>::WithRelativeKernelRadius(
    double relativeKernelRadius)
{
    m_relativeKernelRadius = relativeKernelRadius;
    return static_cast<T&>(*this);
}

class SPHSolver2::Builder final : public SPHSolverBuilderBase2<Builder>
{
 public:
    [[nodiscard]] SPHSolver2 Build() const;

    [[nodiscard]] SPHSolver2Ptr MakeShared() const;
};
}  // namespace CubbyFlow

#endif