Make boundaries to camera

Hello,
i would like to make boundaries for my camera so that it stays in the game field. I've seen many times on the web that the solution would be to clamp the x y z position or set a limit but it's quite impossible in my case (i think) cause my camera is rotated, so every time i move my camera, this is x y and z which change at the same time.
Is there a way to solve this problem ?

Thank you

 

Options:

• Do the math on the clamping zone. Then clamp the camera.
• Add physics colliders around the area and use those to constrain the camera.