Last winter I was working on this city in Carrara 2.0, and I'm picking up where I left off. I've done a lot of modeling, but not much actual animating. Now, I want to install a camera and motion path and back a camera slowly down the street. I'm stymied on the tutorial in the manual...right at the start. After the sphere is installed, the 'add point' button [when clicked on the active plane wall] will not make a point. I feel like I'm overlooking something simple, but what?