푸리에 급수 전개 시각화

\begin{eqnarray}
f(x,y)=\sum_{m=1}^{M}\sum_{n=1}^{N}b_{mn}sin\frac{mπ}{L}x・sin\frac{nπ}{L}y
\end{eqnarray}

// (x,y)での高さを計算
float calcHeight(float x, float y, int N, int M)
{
    float y = 0.0f, temp_y = 0.0f;
    int i, j;
    for (i = 1; i <= N; i++)
    {
        temp_y = sin((float)i*PI*0.5f)*cos((float)i*PI*0.1f*x)/(float)i;
        for (j = 1; j <= M; j++)
        {
            y += tempy*sin((float)j*PI*0.5f)*cos((float)i*PI*0.1f*y)/(float)j;
        }
    }
    y *= 4.0f/(PI*PI);
    return y;
}