Godot Engine – Free and open-source 2D and 3D game engine
I recently got into Panda3d[1]. The Blender3D[2] (an excellent general purpose computer graphics tool) exporter is amazing. I don't even have to change the materials really. The "autoshader" uses blenders normal, emit, spec, and diffuse maps, along with the alpha from PNG's right out of the box.Amazingly easy to use if you like python as well. If you're tired of GUI based game engines, I highly recomend taking a look.EDIT: There is also a physically based shading set-up. But my laptop isn't good enough to play around with it.[1]: http://www.panda3d.org/
[2]: https://store.blender.org/