References

Here's a list of interesting, detailed material on Physically-Based Rendering (within and outside Unity):

• For a deep understanding of Physically-Based Rendering, we recommend you to take a look at The Comprehensive PBR Guide, written by Wes McDermott from Allegorithmic. Allegorithmic's guide takes an in-depth look at the practical and theoretical aspects of PBR, including a great analysis of possible workflows. The guide is freely available in two volumes at http://www.allegorithmic.com/pbr-guide.
• Mastering Physically Based Shading in Unity 5 by Renaldas Zioma (Unity), Erland K?rner (Unity), and Wes McDermott (Allegorithmic), is available at http://www.slideshare.net/RenaldasZioma/unite2014-mastering-physically-based-shading-in-unity-5. This is a detailed presentation about using PBS in Unity. Originally presented at the Unite 2014 conference, it contains some out-of-date information, but it is still worth taking a look at.
• Physically Based Shading in Unity 5 by Aras Pranckevi?ius, from Unity, is available at http://aras-p.info/texts/talks.html. Slides and notes from a presentation on the subject are given at the GDC.
• Tutorial: Physically Based Rendering, And You Can Too! by Joe "EarthQuake" Wilson is available at http://www.marmoset.co/toolbag/learn/pbr-practice. It is a great overview from the makers of Marmoset Toolbag and Skyshop.
• Polycount PBR Wiki, available at http://wiki.polycount.com/wiki/PBR, is a list of resources compiled by the Polycount community.
• Lots of general 3D graphics articles and tutorials from Jeremy Brin of Pixar: http://3drender.com/.