• 1. 摄像机中FOV（Field Of View）属性控制视野角度大小
• 2. FOV代表竖直方向的角度
• 3. 计算横向的角度代码如下

private float GetHorizontalAngle(Camera camera)
{
        float vFOVrad = camera.fieldOfView * Mathf.Deg2Rad;
        float cameraHeightAt1 = Mathf.Tan(vFOVrad * .5f);
        return Mathf.Atan(cameraHeightAt1 * camera.aspect) * 2f * Mathf.Rad2Deg;
}