Learn how to generate beautiful skies with the Sky object in Cinema 4D, and how to export and generate skyboxes for Unity.

(You need Cinema4D 10.111 (or over) with Advanced Render installed.)

Expand the file attached and you will find two files, a C4D project and a unityPackage.

This is how it works:

Open the Speed_Sky.c4d project and you will see a preview of the generated sky thanks to the Sky object. If you select it you can adjust the look of your sky or simply delete it and add a new one.
The camera is already animated to generate the six images needed for the SkyBox. The render settings are 512x512 but you can adjust that.
Only select the path for the rendered images and press shift+R.

The CinemaSky.unityPackage include a material CinemaSky with the six images in place. If you render from C4D directly to the folder NoonSky included, your SkyBox will be updated automatically (you must select NoonSky as the name of your render).

This is the correct order of the images for the SkyBox to look properly (the rendered images from C4D are named with consecutive numbers):

yourskyname0000 - Front
yourskyname0001 - Right
yourskyname0002 - Back
yourskyname0003 - Left
yourskyname0004 - Up
yourskyname0005 - Down