The camera struct maintains all the state of the camera. In order to maintain correct the correct aspect ratio and timing for orbital mechanics, it needs to be updated every frame.
Create a perspective transform that takes eye space coordinates into clip space using field of view and aspect ratio to define the viewing frustrum. We assume that the center of the near plane is also the center of the screen.
Create a perspective transform that takes eye space coordinates into clip space using all the specification needed to defined a viewing frustrum