 return (chebyshev_client_y_center - client_y) / chebyshev_client_y_step;
}

function chebyshev_x_to_client(x){
    return x * chebyshev_client_x_step + chebyshev_client_x_center;
}

function chebyshev_y_to_client(y){
    return chebyshev_client_y_center - y * chebyshev_client_y_step;
}

// Chebyshev points
var chebyshev_xs = [-1.0, -0.8, -0.6, -0.4, -0.2, 0.0, 0.2, 0.4, 0.6, 0.8, 1.0];
var chebyshev_ys = [ 0.1,  0.2,  0.3,  0.4,  0.5, 0.6, 0.5, 0.4, 0.3, 0.2, 0.1];
var chebyshev_n = 11;
var chebyshev_i = 0