Horizon very far off

Project:The Wall
Component:Code
Category:feature request
Priority:normal
Assigned:Unassigned
Status:active
Project wiki:The Wall: animation project
Description

I want to create a very flat world. The horizon will often be visible in the camera view. The horizon is very far away, and very flat, as if the earth was a perfect sphere and very large (like our own).
I can add a plane and make it very large, but then the render time is tremendously increased even with the most modest scene.

Use do clippings ?