3rd person camera that avoids objects

I am looking for a camera script to for a 3rd person shooter game. Being rubbish at scripting, I managed to make one where the camera got closer to the player depending on its upward rotation, it worked alright, but wasn't great. I would prefer to have it so the camera stays at a fixed distance unless it has to avoid and object. This means if I made the character look up, the camera would stay at x distance until it touched the ground, when it would slide along the ground.

This is like the WOW-like camera script example except I want to be able to look up and down as well but I can't implement it because I wouldn't know how.

Thanks