Building lighting stuck at 0%

I’m pretty new to this.

I’ve got a relatively simple map with only a few actors - although they are from the Kite demo kit and rather large. Once I started adding a few copies of the big rocks, lighting stopped generating.

It works to move around the preview/editor, but when I go to build lighting it never gets past 0% even after an hour.

The computer still works fine, its just stuck here. Here’s a screen.

I’m on a macbook pro laptop with 16 gigs of ram.

Here’s a screen shot.