Ok I compiled it from sources and decided to test. For the sake of it I used broadleaf tree, single landscape (2k) and dynamic lights.
With distance field enabled rendering something like 650 instanced of this tree took 22ms (about 44fps).
Rendering without distance fields took like 18ms (about 55fps).
At this point, I think the bigger problem was amount of trees, than the fact they had distance fields on them. In more realistic scenarios you would probabaly never rendering this amount of things at once.
One problem I noticed though is that seem like Distance field shadows got backfired, since they seem to not work, even though, they are enabled.
Bah. For some reason DistanceFieldShadowing variable was on 0.
Now difference between enabled and disabled GI on the same scene is about 2ms. And that’s on Draw (draw is CPU time ?).
For me that’s good enough! To be perfectly useable. Especially in more realistic scenario, than spamming trees all around on giant landscape load entirely at once ;).
I’m impressed. Waiting for more informations!.
Edit:
To be clear. Enabling DFAO on tree + GI is well worth it, since they look like 10x times better with AO alone ;).
And I used the foliage lighting model in material.