PBDCollisionSphereConstraints.h

Go to the documentation of this file.

// Copyright Epic Games, Inc. All Rights Reserved.
#pragma once
 
#if !COMPILE_WITHOUT_UNREAL_SUPPORT
#include "Chaos/Array.h"
#include "Chaos/BoundingVolumeHierarchy.h"
#include "Chaos/Framework/Parallel.h"
#include "Chaos/Map.h"
#include "Chaos/PBDParticles.h"
#include "Chaos/PerParticleRule.h"
#include "Chaos/Sphere.h"
 
#include <algorithm>
 
// This is an approximation but only collides with spheres in the velocity direction which can hurt compared to all directions when it comes to thickness
namespace Chaos
{
class FPBDCollisionSphereConstraints : public FPerParticleRule
{
  public:
      FPBDCollisionSphereConstraints(const FPBDParticles& InParticles, const TSet<TVec2<int32>>& DisabledCollisionElements, const FReal Dt, const FReal Height = (FReal)0.)
        : MH(Height)
    {
        for (int32 i = 0; i < (int32)InParticles.Size(); ++i)
        {
            MObjects.Add(Chaos::FImplicitObjectPtr(new FSphere(InParticles.P(i), Height)));
        }
        TBoundingVolumeHierarchy<TArray<Chaos::FImplicitObjectPtr>, TArray<int32>> Hierarchy(MObjects);
        FCriticalSection CriticalSection;
        PhysicsParallelFor(InParticles.Size(), [&](int32 Index) {
            TArray<int32> PotentialIntersections = Hierarchy.FindAllIntersections(InParticles.P(Index));
            for (int32 i = 0; i < PotentialIntersections.Num(); ++i)
            {
                int32 Index2 = PotentialIntersections[i];
                if (Index == Index2 || DisabledCollisionElements.Contains(TVector<int32, 2>(Index, Index2)))
                    continue;
                if ((InParticles.P(Index2) - InParticles.P(Index)).Size() < Height)
                {
                    CriticalSection.Lock();
                    MConstraints.FindOrAdd(Index).Add(Index2);
                    CriticalSection.Unlock();
                }
            }
        });
    }
    virtual ~FPBDCollisionSphereConstraints() {}
 
    void Apply(FPBDParticles& InParticles, const FReal Dt, const int32 Index) const override //-V762
    {
        if (InParticles.InvM(Index) == 0 || !MConstraints.Contains(Index))
            return;
        for (int32 i = 0; i < MConstraints[Index].Num(); ++i)
        {
            FVec3 Normal;
            FReal Phi = MObjects[MConstraints[Index][i]]->PhiWithNormal(InParticles.P(Index), Normal);
            if (Phi < 0)
            {
                InParticles.P(Index) += -Phi * Normal;
            }
        }
    }
 
  private:
    FReal MH;
    TMap<int32, TArray<int32>> MConstraints;
    TArray<Chaos::FImplicitObjectPtr> MObjects;
};
 
template <typename T, int d>
using TPBDCollisionSphereConstraints UE_DEPRECATED(4.27, "Deprecated. this class is to be deleted, use FPBDCollisionSphereConstraints instead") = FPBDCollisionSphereConstraints;
 
}
#endif