Fly Through with Surrounding Background

There is no real need for a huge working space for a large 3D fly-through. 3D layers can exist at the edge of a standard HD frame until they are needed. In these scenarios, it is almost always a better idea to move the actors (layers I often call my 3D layers actors) than it is to move the camera. 

It is also a great temptation to try and cover way too much time in a single comp. If there is a place to cut your shot, even do a match cut, then break up your comp into shorter sections and do the final edit in Premiere Pro.

Shortly after 3D layers were introduced in After Effects I created a fly-over of the entire WWII war in the pacific. It was about a five-minute scene. At first, I tried to arrange the stage with all of the layers distributed in 3D space in a single comp. It was a mess. I then rethought the entire workflow and set up about 30 separate layered Illustrator files, some with the same background layers. Each AI file was imported as a separate composition, the layers were arranged in 3D space using 4 views, and then a 3D Null was added to act as the parent for all of the actors. I flew the null through the scene by animating only the position. The camera was animated in Y and X with the point of interest always at the comp center si I could easily get any angle on my 3D scenes and find the starting point for the next comp with ease.

Some of my actors moved in the scene, like ships moving at the battle of midway, and there were animated arrows showing movements, but all of the transitions between different stages (comps) were handled by matching up first and last frames with the first and last frame of the preceding comps (shots). The project became manageable, changes requested by the director took a few minutes instead of a few days, I don't think I had a single comp longer than about 10 seconds which was a single sentence of narration, and 2 weeks before the deadline the rendered file was sitting on the editors' desk. If I had kept the project as one comp and tried to fly the camera through the whole thing it would have taken me forever and changes would have taken days to render. 

If you would like to share some screenshots I can probably give you some decent workflow suggestions. A 50K X 50K master comp with everything in it is probably not a very good idea at all.

I'm pretty sure you will have problems working on a 50000px composition in a 3D space. Anyway, you can create you 3D background using some techniques:

1.- Create a Cinema 4D file with a Sky with any texture. Import this native Cinema 4D file into your composition and chage the Cineware camera options to Centered Camera Comp. This way this "infinite 3D" sphere will act as a background reacting to the movement of your camera.

2.- Change your composition renderer to Cinema 4D reneder . This way you can create a curvature for any kind of layer to create a semi-cylindrical environment (you can duplicate and rotate this layer to create a complete cylindrical environmet).