Spring.h

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#ifndef ULT_PHYSICS_SPRING_H_INCLUDED
#define ULT_PHYSICS_SPRING_H_INCLUDED
 
#include "PointMass.h"
 
namespace Ult
{

class SpringMass : public PointMass
{
public:
    SpringMass() :
        mNormal(),
        mFixed(false)
    {}

    Vector3D GetNormal() const { return mNormal; }

    Vector3D* GetNormalPtr() { return &mNormal; }

    void SetNormal(const Vector3D& n) { mNormal = n; }

    void NormalizeNormal() { mNormal.Normalize(); }

    bool IsFixed() const { return mFixed; }

    void SetIsFixed(const bool val) { mFixed = val; }
 
private:
    Vector3D mNormal;
    bool mFixed;
};

class Spring
{
public:
    Spring() :
        mBall1(nullptr),
        mBall2(nullptr),
        mTension(0.0f),
        mConstant(0.0f),
        mLength(0.0f)
    {}

    ~Spring()
    {}

    void SetSpring(float t, float c, float l, SpringMass* m1, SpringMass* m2)
    {
        mBall1 = m1;
        mBall2 = m2;
        mTension = t;
        mConstant = c;
        mLength = l;
    }

    void Update()
    {
        if (!mBall1 || !mBall2) { return; }
        Vector3D springVec = mBall2->GetPosition() - mBall1->GetPosition();
        mTension = mConstant * (springVec.Magnitude() - mLength) / mLength;
        springVec.Normalize();
        mBall1->AddForce(springVec * mTension);
        mBall2->AddForce((springVec * mTension) * -1.0f);
    }
 
private:
    SpringMass* mBall1, *mBall2;
    float mTension, mConstant, mLength;
};
 
} // namespace Ult
 
#endif // ULT_PHYSICS_SPRING_H_INCLUDED