PBDCollisionSolverUtilities.h

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// Copyright Epic Games, Inc. All Rights Reserved.
#pragma once
 
#include "Chaos/Core.h"
#include "Chaos/Defines.h"
#include "Chaos/Evolution/SolverBody.h"
 
 
namespace Chaos
{
    namespace Private
    {
 
        inline bool CalculateBodyShockPropagation(
            const FSolverBody& Body0,
            const FSolverBody& Body1,
            const FSolverReal ShockPropagation,
            FSolverReal& OutShockPropagation0,
            FSolverReal& OutShockPropagation1)
        {
            OutShockPropagation0 = FSolverReal(1);
            OutShockPropagation1 = FSolverReal(1);
 
            // Shock propagation decreases the inverse mass of bodies that are lower in the pile
            // of objects. This significantly improves stability of heaps and stacks. Height in the pile is indictaed by the "level". 
            // No need to set an inverse mass scale if the other body is kinematic (with inv mass of 0).
            // Bodies at the same level do not take part in shock propagation.
            if (Body0.IsDynamic() && Body1.IsDynamic() && (Body0.Level() != Body1.Level()))
            {
                // Set the inv mass scale of the "lower" body to make it heavier
                if (Body0.Level() < Body1.Level())
                {
                    OutShockPropagation0 = ShockPropagation;
                }
                else
                {
                    OutShockPropagation1 = ShockPropagation;
                }
                return true;
            }
 
            return false;
        }
 
    } // namespace Private
} // namespace Chaos