shadow detection in opencv code

//shadow detection performed per pixel
// should work for rgb data, could be usefull for gray scale and depth data as well
//  See: Prati,Mikic,Trivedi,Cucchiarra,"Detecting Moving Shadows...",IEEE PAMI,2003.
CV_INLINE int _icvRemoveShadowGMM(float* data, int nD,
                                unsigned char nModes, 
                                CvPBGMMGaussian* pGMM,
                                float m_fTb,
                                float m_fTB,    
                                float m_fTau)
{
    float tWeight = 0;
    float numerator, denominator;
    // check all the components  marked as background:
    for (int iModes=0;iModes<nModes;iModes++)
    {

        CvPBGMMGaussian g=pGMM[iModes];

        numerator = 0.0f;
        denominator = 0.0f;
        for (int iD=0;iD<nD;iD++)
        {
                numerator   += data[iD]  * g.mean[iD];
                denominator += g.mean[iD]* g.mean[iD];
        }

        // no division by zero allowed
        if (denominator == 0)
        {
                return 0;
        };
        float a = numerator / denominator;

        // if tau < a < 1 then also check the color distortion
        if ((a <= 1) && (a >= m_fTau))
        {

            float dist2a=0.0f;
            
            for (int iD=0;iD<nD;iD++)
            {
                float dD= a*g.mean[iD] - data[iD];
                dist2a += (dD*dD);
            }

            if (dist2a<m_fTb*g.variance*a*a)
            {
                return 2;
            }
        };

        tWeight += g.weight;
        if (tWeight > m_fTB)
        {
                return 0;
        };
    };
    return 0;
}