Camera controller

I’d like to discuss the way the camera moves now. When the camera is looking directly at the earth’s surface, rotation while the camera is moving is achieved by changing x and z. When the camera is at an angle to the ground, rotation while the camera is moving is achieved by changing x and y. Now I want the camera to achieve the effect of abandoning the z-axis rotation by changing x and y even when the camera is looking directly at the earth’s surface. Any ideas?

It might help to take a step back and start with what you’re actually trying to achieve. I’m perhaps stating the obvious, but because the Earth is round, the direction of “down” changes depending on where you are on the globe and how are away that location is from the CesiumGeoreference origin.