/* distance v1 to line-piece v2-v3 in 3D */
float PdistVL3Dfl(float *v1, float *v2, float *v3)
{
    float lambda, cp[3], len;

    lambda= lambda_cp_line_ex(v1, v2, v3, cp);

    if(lambda <= 0.0f)
        return VecLenf(v1, v2);
    else if(lambda >= 1.0f)
        return VecLenf(v1, v3);
    else
        return VecLenf(v1, cp);
}