ParticleSystemSolver2.h

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/*************************************************************************
> File Name: ParticleSystemSolver2.h
> Project Name: CubbyFlow
> Author: Chan-Ho Chris Ohk
> Purpose: Basic 2-D particle system solver.
> Created Time: 2017/05/20
> Copyright (c) 2018, Chan-Ho Chris Ohk
*************************************************************************/
#ifndef CUBBYFLOW_PARTICLE_SYSTEM_SOLVER2_H
#define CUBBYFLOW_PARTICLE_SYSTEM_SOLVER2_H

#include <Core/Animation/PhysicsAnimation.h>
#include <Core/Collider/Collider2.h>
#include <Core/Emitter/ParticleEmitter2.h>
#include <Core/Field/VectorField2.h>
#include <Core/Particle/ParticleSystemData2.h>
#include <Core/Utils/Constants.h>
#include <Core/Vector/Vector2.h>

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

        ParticleSystemSolver2();

        ParticleSystemSolver2(double radius, double mass);

        virtual ~ParticleSystemSolver2();

        double GetDragCoefficient() const;

        void SetDragCoefficient(double newDragCoefficient);

        double GetRestitutionCoefficient() const;

        void SetRestitutionCoefficient(double newRestitutionCoefficient);

        const Vector2D& GetGravity() const;

        void SetGravity(const Vector2D& newGravity);

        const ParticleSystemData2Ptr& GetParticleSystemData() const;

        const Collider2Ptr& GetCollider() const;

        void SetCollider(const Collider2Ptr& newCollider);

        const ParticleEmitter2Ptr& GetEmitter() const;

        void SetEmitter(const ParticleEmitter2Ptr& newEmitter);

        const VectorField2Ptr& GetWind() const;

        void SetWind(const VectorField2Ptr& newWind);

        static Builder GetBuilder();

    protected:
        void OnInitialize() override;

        void OnAdvanceTimeStep(double timeStepInSeconds) override;

        virtual void AccumulateForces(double timeStepInSeconds);

        virtual void OnBeginAdvanceTimeStep(double timeStepInSeconds);

        virtual void OnEndAdvanceTimeStep(double timeStepInSeconds);

        void ResolveCollision();

        void ResolveCollision(
            ArrayAccessor1<Vector2D> newPositions,
            ArrayAccessor1<Vector2D> newVelocities);

        void SetParticleSystemData(const ParticleSystemData2Ptr& newParticles);

    private:
        double m_dragCoefficient = 1e-4;
        double m_restitutionCoefficient = 0.0;
        Vector2D m_gravity = Vector2D(0.0, GRAVITY);

        ParticleSystemData2Ptr m_particleSystemData;
        ParticleSystemData2::VectorData m_newPositions;
        ParticleSystemData2::VectorData m_newVelocities;
        Collider2Ptr m_collider;
        ParticleEmitter2Ptr m_emitter;
        VectorField2Ptr m_wind;

        void BeginAdvanceTimeStep(double timeStepInSeconds);

        void EndAdvanceTimeStep(double timeStepInSeconds);

        void AccumulateExternalForces();

        void TimeIntegration(double timeStepInSeconds);

        void UpdateCollider(double timeStepInSeconds) const;

        void UpdateEmitter(double timeStepInSeconds) const;
    };

    using ParticleSystemSolver2Ptr = std::shared_ptr<ParticleSystemSolver2>;
    
    template <typename DerivedBuilder>
    class ParticleSystemSolverBuilderBase2
    {
    public:
        DerivedBuilder& WithRadius(double radius);

        DerivedBuilder& WithMass(double mass);

    protected:
        double m_radius = 1e-3;
        double m_mass = 1e-3;
    };

    template <typename T>
    T& ParticleSystemSolverBuilderBase2<T>::WithRadius(double radius)
    {
        m_radius = radius;
        return static_cast<T&>(*this);
    }

    template <typename T>
    T& ParticleSystemSolverBuilderBase2<T>::WithMass(double mass)
    {
        m_mass = mass;
        return static_cast<T&>(*this);
    }

    class ParticleSystemSolver2::Builder final :
        public ParticleSystemSolverBuilderBase2<ParticleSystemSolver2::Builder>
    {
    public:
        ParticleSystemSolver2 Build() const;

        ParticleSystemSolver2Ptr MakeShared() const;
    };
}

#endif