PerParticlePBDSpringConstraints.h

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// Copyright Epic Games, Inc. All Rights Reserved.
#pragma once
 
#include "Chaos/PBDSpringConstraintsBase.h"
 
namespace Chaos::Softs
{
 
class UE_DEPRECATED(5.0, "Per particle constraint rules are no longer used by the cloth solver. Use FPBDSpringConstraints instead.") FPerParticlePBDSpringConstraints : public FPBDSpringConstraintsBase
{
    typedef FPBDSpringConstraintsBase Base;
    using Base::Constraints;
    using Base::Stiffness;
 
public:
    FPerParticlePBDSpringConstraints(const FSolverParticles& InParticles, const TArray<TVec2<int32>>& InConstraints, const FSolverReal InStiffness = (FSolverReal)1.)
        : Base(InParticles, 0, 0, InConstraints, TConstArrayView<FRealSingle>(), FSolverVec2(InStiffness))
    {
        for (int32 i = 0; i < Constraints.Num(); ++i)
        {
            const auto& Constraint = Constraints[i];
            int32 i1 = Constraint[0];
            int32 i2 = Constraint[1];
            if (i1 >= ParticleToConstraints.Num())
            {
                ParticleToConstraints.SetNum(i1 + 1);
            }
            if (i2 >= ParticleToConstraints.Num())
            {
                ParticleToConstraints.SetNum(i2 + 1);
            }
            ParticleToConstraints[i1].Add(i);
            ParticleToConstraints[i2].Add(i);
        }
    }
    virtual ~FPerParticlePBDSpringConstraints() override {}
 
    // TODO(mlentine): We likely need to use time n positions here
    void Apply(FSolverParticles& InParticles, const FSolverReal Dt, const int32 Index) const
    {
        for (int32 i = 0; i < ParticleToConstraints[Index].Num(); ++i)
        {
            int32 CIndex = ParticleToConstraints[Index][i];
            const auto& Constraint = Constraints[CIndex];
            int32 i1 = Constraint[0];
            int32 i2 = Constraint[1];
            if (Index == i1 && InParticles.InvM(i1) > 0)
            {
                InParticles.P(i1) -= InParticles.InvM(i1) * Base::GetDelta(InParticles, CIndex, (FSolverReal)Stiffness);
            }
            else if (InParticles.InvM(i2) > 0)
            {
                check(Index == i2);
                InParticles.P(i2) += InParticles.InvM(i2) * Base::GetDelta(InParticles, CIndex, (FSolverReal)Stiffness);
            }
        }
    }
 
private:
    TArray<TArray<int32>> ParticleToConstraints;
};
 
}  // End namespace Chaos::Softs