PerParticlePBDTetConstraints.h

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// Copyright Epic Games, Inc. All Rights Reserved.
#pragma once
 
#include "Chaos/PBDSoftsSolverParticles.h"
#include "Chaos/PBDTetConstraintsBase.h"
 
namespace Chaos::Softs
{
 
class UE_DEPRECATED(5.0, "Per particle constraint rules are no longer used by the cloth solver. Use Softs::FPBDTetConstraints instead.") FPerParticlePBDTetConstraints : public Softs::FPBDTetConstraintsBase
{
    typedef Softs::FPBDTetConstraintsBase Base;
    using Base::Constraints;
 
  public:
      FPerParticlePBDTetConstraints(const FSolverParticles& InParticles, TArray<TVec4<int32>>&& InConstraints, const FSolverReal InStiffness = (FSolverReal)1.)
        : Base(InParticles, MoveTemp(InConstraints), InStiffness)
    {
        for (int32 i = 0; i < Constraints.Num(); ++i)
        {
            const TVec4<int32>& Constraint = Constraints[i];
            int32 i1 = Constraint[0];
            int32 i2 = Constraint[1];
            int32 i3 = Constraint[2];
            int32 i4 = Constraint[3];
            if (i1 >= ParticleToConstraints.Num())
            {
                ParticleToConstraints.SetNum(i1 + 1);
            }
            if (i2 >= ParticleToConstraints.Num())
            {
                ParticleToConstraints.SetNum(i2 + 1);
            }
            if (i3 >= ParticleToConstraints.Num())
            {
                ParticleToConstraints.SetNum(i3 + 1);
            }
            if (i4 >= ParticleToConstraints.Num())
            {
                ParticleToConstraints.SetNum(i4 + 1);
            }
            ParticleToConstraints[i1].Add(i);
            ParticleToConstraints[i2].Add(i);
            ParticleToConstraints[i2].Add(i);
            ParticleToConstraints[i2].Add(i);
        }
    }
    virtual ~FPerParticlePBDTetConstraints() override
    {
    }
 
    void Apply(FSolverParticles& InParticles, const FSolverReal Dt, const int32 Index) const
    {
        for (int i = 0; i < ParticleToConstraints[Index].Num(); ++i)
        {
            int32 CIndex = ParticleToConstraints[Index][i];
            const TVec4<int32>& Constraint = Constraints[CIndex];
            int32 i1 = Constraint[0];
            int32 i2 = Constraint[1];
            int32 i3 = Constraint[2];
            int32 i4 = Constraint[3];
            const TVec4<FSolverVec3> Grads = Base::GetGradients(InParticles, CIndex);
            const FSolverReal S = Base::GetScalingFactor(InParticles, CIndex, Grads);
            if (Index == i1)
            {
                InParticles.P(i1) -= S * InParticles.InvM(i1) * Grads[0];
            }
            else if (Index == i2)
            {
                InParticles.P(i2) -= S * InParticles.InvM(i2) * Grads[1];
            }
            else if (Index == i3)
            {
                InParticles.P(i3) -= S * InParticles.InvM(i3) * Grads[2];
            }
            else
            {
                check(Index == i4);
                InParticles.P(i4) -= S * InParticles.InvM(i4) * Grads[3];
            }
        }
    }
 
  private:
    TArray<TArray<int32>> ParticleToConstraints;
};
 
}  // End namespace Chaos::Softs