这个相机旋转算法有什么问题？

I'm trying to implement 3d graphics for a small game I'm working on, and the camera rotation isn't working quite right. For the camera, I am using a spherical coordinate system, with alpha as the azimuthal angle (theta in the picture) and beta as 90 - the polar angle (90 - phi in the picture):I'm trying to implement 3d graphics for a small