This is a tutorial detailing how to set up directional lighting in your custom SWBF2 map. I originally wrote this several years ago for someone on Gametoast. The original post can be found here and is as follows:
Here's what you'll need to make your map run beautifully and look beautiful.
In Zero Editor, open up your map (make sure you have "Build accurate object collision" checked) and go to the "Light" tab.
Create a new light, place it literally wherever you want in your map (I usually place mine in the general area where the sun is), and call it "Sun"; change its type to "Dir", for "directional," and change its settings so "Cast Specular" and "Cast Shadows" are enabled; oh, and probably change the color of the light to whatever you please as well - probably at least make it a bit darker than
(255, 255, 255) since
(255, 255, 255) will make your units that have specular glow like crazy.
Now over to the right, type "Sun" into the text field under "Directional Light 1" and change the Top Ambient and Bottom Ambient Colors to whatever you please.
Finally, click on the "Image" button, make sure "Burn Object Shadows" is set to "Yes," and click "Burn Terrain."