I was wondering how you would go about putting a 3D object into a photograph so that portions of the image are:

1. In front of, or
2. Behind the model.

For example, a photo taken from the roadside with a tree in the foreground. I want to show a 3D model of a car in the photo on the road but a section of it is not visible because it is obscured by the tree.

Is this possible? If so, how can you do it?

Thanks in advance.