Esenthel Game Engine ( http://esenthel.com/ ) now has full support of PBR.
This includes realistic GGX specular, environment map, smoothness/roughness/gloss, reflectivity, multi-scattering energy preservation, Burley/Disney based diffuse shading.
It's a lot more advanced than the previous shading model!
Here's an example of new rendering:
And as if turned to metal:
And here's a slideshow comparing old vs new rendering system:
https://www.facebook.com/EsenthelEngine/photos/pcb.2777773715589925/2777771278923502/?type=3&theater
Esenthel is a very powerful, free, open source and cross-platform Game Engine.
Thanks!