PerCellBoundaryConditions.h

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// Copyright Epic Games, Inc. All Rights Reserved.
#pragma once
 
// HEADER_UNIT_SKIP - Not included directly
 
#include "Chaos/KinematicGeometryParticles.h"
#include "Chaos/Transform.h"
 
namespace Chaos
{
template<class T, int d>
class TPerCellBoundaryConditions
{
  public:
    TPerCellBoundaryConditions(const TKinematicGeometryParticles<T, d>& CollisionParticles, const TKinematicGeometryParticles<T, d>& SourceParticles)
        : MParticles(CollisionParticles), MSources(SourceParticles) {}
    ~TPerCellBoundaryConditions() {}
 
    void ApplyNeumann(const TUniformGrid<T, d>& Grid, TArrayFaceND<bool, d>& BoundaryConditions, TArrayFaceND<T, d>& Velocity, const T Dt, const Pair<int32, TVector<int32, d>>& Index)
    {
        BoundaryConditions(Index) = false;
        for (uint32 i = 0; i < MParticles.Size(); ++i)
        {
            const TVector<T, d>& X = Grid.Location(Index);
            TRigidTransform<T, d> Frame(MParticles.GetX(i), MParticles.GetR(i));
            if (MParticles.GetGeometry(i)->SignedDistance(Frame.InverseTransformPosition(X)) < 0)
            {
                BoundaryConditions(Index) = true;
                Velocity(Index) = MParticles.GetV(i)[Index.First];
                break;
            }
        }
        for (uint32 i = 0; i < MSources.Size(); ++i)
        {
            const TVector<T, d>& X = Grid.Location(Index);
            TRigidTransform<T, d> Frame(MSources.GetX(i), MSources.GetR(i));
            if (MSources.GetGeometry(i)->SignedDistance(Frame.InverseTransformPosition(X)) < 0)
            {
                BoundaryConditions(Index) = true;
                Velocity(Index) = MSources.GetV(i)[Index.First];
                break;
            }
        }
    }
 
    void ApplyDirichlet(const TUniformGrid<T, d>& Grid, TArrayND<bool, d>& BoundaryConditions, TArrayND<T, d>& Density, const T Dt, const TVector<int32, d>& Index)
    {
        BoundaryConditions(Index) = false;
        // This is not a real boundary condition; just a convinient place to set density from sources
        for (uint32 i = 0; i < MSources.Size(); ++i)
        {
            const TVector<T, d>& X = Grid.Location(Index);
            TRigidTransform<T, d> Frame(MSources.GetX(i), MSources.GetR(i));
            if (MSources.GetGeometry(i)->SignedDistance(Frame.InverseTransformPosition(X)) < 0)
            {
                Density(Index) = 1.f;
                break;
            }
        }
    }
 
  private:
    const TKinematicGeometryParticles<T, d>& MParticles;
    const TKinematicGeometryParticles<T, d>& MSources;
};
}