Ok so I just got done watching this video UE4 Features Trailer 2015 | Unreal Engine - YouTube. Which at the time that I posted it points out the feature of dynamic global illumination from heightfields. I was immediately dumbfounded as I never even heard of the technique. What is it and how is it done?
It takes the heightfield from the landscape and uses it for very efficient global illumination, so the light only bounces from the landscape. It’s not yet in 4.7 but will be in 4.8.
Very very cool. When you say it will be in 4.8… how will I enable it when it ships in 4.8?
I have no idea since 4.8 is not yet out so there is no documentation about that.
It will be in 4.8 but disabled by default as it needs a bit more work.
Fair enough 
“From heightfields”… does this mean that it can´t be used in closed environments without landscape height data, i.e. houses, caves, etc?
That seems to be very interesting for my project. I’m really looking forward to 4.8 and some improvement in the future.
If somebody is interested in read into this topic, here is a nice paper from Microsoft Research, even if it’s a bit mathematical. 
Probably not going to find out a lot of information concerning specifics just yet - it still needs some work, and things are likely to change before it is implemented and widely used.