c++ - 将两种方法结合在一起

Question

以下两个函数计算 obj 类型对象的体积力。第一个函数调用第二个函数两次，有没有办法将这些方法组合在一起？

void calculateBodyForcesForEach(obj *pBody, obj *pHead, sys *sys) {
    float fTotalForce[4] = {0.0f};

     calculateBodyForces(pBody, sys->m_pSun, fTotalForce, sys);


     for (obj *pOtherBody = pHead; pOtherBody;) {       
         if (pBody != pOtherBody) {
             calculateBodyForces(pBody, pOtherBody, fTotalForce, sys);
         }
         pOtherBody = pOtherBody->m_pNext;
     }  

     vecCopy(fTotalForce, pBody->m_fForce);
}

void calculateBodyForces(obj *pBody, obj *pOtherBody, 
                         float *fTotalForce, solarSystem *sys) 
{
    pBody->m_fForce[0] = 0.0f;
    pBody->m_fForce[1] = 0.0f;
    pBody->m_fForce[2] = 0.0f;

    float fCalculatedForce[3] = {0.0f};

    float fCalculatedMass = pBody->m_fMass * pOtherBody->m_fMass;

    float fDistanceBetweenPos[3] = {0.0f};
    vecSub(pOtherBody->m_fPosition, pBody->m_fPosition, fDistanceBetweenPos);

    float fDistanceSquared = (fDistanceBetweenPos[0] * fDistanceBetweenPos[0]) + (fDistanceBetweenPos[1] * fDistanceBetweenPos[1]) + (fDistanceBetweenPos[2] * fDistanceBetweenPos[2]);         

    float fUnitVector[3] = {0.0f};
    vecSub(pOtherBody->m_fPosition, pBody->m_fPosition, fUnitVector);
    vecNormalise(fUnitVector, fUnitVector);

    float fGravitationalForce = sys->m_fGravitationalConstant * (fCalculatedMass / fDistanceSquared);

    vecScalarProduct(fUnitVector, fGravitationalForce, fCalculatedForce);

    vecAdd(fTotalForce, fCalculatedForce, fTotalForce); 
}

//////到目前为止我的解决方案但仍然不起作用

void calculateVelocityAndPosition(planet *pElement, solarSystem *pSystem) { //completly modified  

    float fStartPosition[4] = {0.0f,0.0f,0.0f,0.0f};
    float fAccelerationTime[3] = {0.0f,0.0f,0.0f};
    float fVelocityInterval[3] = {0.0f,0.0f,0.0f};
    float fTotalCalculated[3] = {0.0f,0.0f,0.0f};
    vecCopy(pElement->m_fPosition, fStartPosition);
    vecScalarProduct(pElement->m_fAcceleration, pSystem->m_fTimeStep * pSystem->m_fTimeStep, fAccelerationTime);
    vecScalarProduct(fAccelerationTime, 0.5f, fAccelerationTime);
    vecScalarProduct(pElement->m_fVelocity, pSystem->m_fTimeStep, fVelocityInterval);
    vecAdd(fVelocityInterval, fAccelerationTime, fTotalCalculated);
    vecAdd(fStartPosition, fTotalCalculated, pElement->m_fPosition);
    fori(3){
    pElement->m_fVelocity[i] = (pElement->m_fPosition[i] - fStartPosition[i]) / pSystem->m_fTimeStep;
    }
    fori(3)
     if (pElement->m_fVelocity[i] > pSystem->m_fMaxVelocity)
     pElement->m_fVelocity[i] = pSystem->m_fMaxVelocity;
     else if (pElement->m_fVelocity[i] < pSystem->m_fMaxNegativeVelocity)
     pElement->m_fVelocity[i] = pSystem->m_fMaxNegativeVelocity;
    vecScalarProduct(pElement->m_fVelocity, pSystem->m_fDragCoefficient, pElement->m_fVelocity);
}

Answer 1

fori(3)

这是什么意思？

这个金额:

float fDistanceSquared = (fDistanceBetweenPos[0] * fDistanceBetweenPos[0]) + (fDistanceBetweenPos[1] * fDistanceBetweenPos[1]) + (fDistanceBetweenPos[2] * fDistanceBetweenPos[2]);

最好用它制作一个循环:

float fDistanceSquared = 0.0f
for (int i = 0; i<3; i++)
 fDistanceSquared += fDistanceBetweenPos[i] * fDistanceBetweenPos[i];

如何确定标量积？为什么里面有三个变量呢？此外，了解正在解决的问题可能会有所帮助。