ParticleCollisions.h

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// Copyright Epic Games, Inc. All Rights Reserved.
#pragma once
 
#include "CoreMinimal.h"
#include "Chaos/Core.h"
 
#include "Chaos/Collision/CollisionVisitor.h"
#include "Chaos/ParticleHandleFwd.h"
 
namespace Chaos
{
    class FParticlePairMidPhase;
 
    class FParticleCollisions
    {
    public:
        // In a mostly stationary scene the choice of container doesn't matter much. In a highly dynamic
        // scene it matters a lot. This was tested with TMap, TSortedMap, and TArray. TArray was better in all cases.
        // We store the list of overlapping particle pairs for every particle. This list can get quite
        // large for world objects. We need to make sure that Add / Remove are not O(N).
        // We also search this list to find an existing MidPhase for a specific particle pair. However
        // we always search the particle with the fewest overlaps, which will be a dynamic particle
        // that should not have too many contacts. 
        using FContainerType = TArray<TPair<uint64, FParticlePairMidPhase*>>;
 
        CHAOS_API FParticleCollisions();
        CHAOS_API ~FParticleCollisions();
 
        inline int32 Num() const 
        { 
            return MidPhases.Num();
        }
 
        inline void Reset()
        {
            MidPhases.Reset();
        }
 
        CHAOS_API void AddMidPhase(FGeometryParticleHandle* InParticle, FParticlePairMidPhase* InMidPhase);
 
        CHAOS_API void RemoveMidPhase(FGeometryParticleHandle* InParticle, FParticlePairMidPhase* InMidPhase);
 
        inline FParticlePairMidPhase* GetMidPhase(const int32 InIndex)
        {
            if (MidPhases.IsValidIndex(InIndex))
            {
                return MidPhases[InIndex].Value;
            }
            return nullptr;
        }
 
        inline FParticlePairMidPhase* FindMidPhase(const uint64 InKey)
        {
            for (int32 Index = 0; Index < MidPhases.Num(); ++Index)
            {
                if (MidPhases[Index].Key == InKey)
                {
                    return MidPhases[Index].Value;
                }
            }
            return nullptr;
        }
 
        template<typename TLambda>
        inline ECollisionVisitorResult VisitMidPhases(const TLambda& Lambda);
 
        template<typename TLambda>
        inline ECollisionVisitorResult VisitConstMidPhases(const TLambda& Lambda) const;
 
        template<typename TLambda>
        inline ECollisionVisitorResult VisitCollisions(const TLambda& Visitor, const ECollisionVisitorFlags VisitFlags = ECollisionVisitorFlags::VisitDefault);
 
        template<typename TLambda>
        inline ECollisionVisitorResult VisitConstCollisions(const TLambda& Visitor, const ECollisionVisitorFlags VisitFlags = ECollisionVisitorFlags::VisitDefault) const;
 
    private:
        FContainerType MidPhases;
    };
 
}