I have a problem. It is the first project in which I want to use 3d layers and cameras. The project I have is a landscape pan, like if you were in a car filming another car.
I already have built all the landscape with 3d layers, one for the mountains, one for the nearest grass, some for trees in different depth, I have also a car that moves from the left side of the composition and goes through the right size. The composition with the landscape is 12800 x 720 (10 times wider than normal 720p).
What I want to do is to set a camera layer that just film a 720p size of the big comp, to could move it as I want along the landscape. I do not know how to do it because when i set the camera layer it sees all the comp and not an small part of it as I want to.
Not sure you can actually resize a camera for a specific size in AE. However you can have stuff off the sides of a comp in After effects in 3D space. So you can resize the comp back to 1280x720 then just pan the camera right and left without any problems.
If you wanted to keep it the long comp you could place the long comp in another comp sized to 1280x720 then frame it in the middle. Then using a camera in the long comp pan it around keeping in mind what you want to keep in frame. I think the first way I mentioned would be easier though.