Earth curvature and horizon in modeling large scenes If I want to model a large environment, how can I solve the problem of earth curvature and horizon?

I use an environment map for the sky, but for the ground what can I do?

Do I have to model the ground with a big plane, disk or a spherical cap?

Is there a general procedure to solve this problem in computer graphics?
Having the horizon fall off is simply dropping the ground in the distance down somewhat.

A point $x$ km away if you follow the curve of the planet will be $r-r\cdot \cos \frac{x}{r}$ down and $r\cdot \sin \frac{x}{r}$ out horizontally where $r$ is the radius of the planet you are modeling (~6.3k km for earth). In the vertex shader you can account for that before you apply the view and projection matrix.