Another shout-out to my work with IMG - this one is my favorite.

It is a document I wrote to explain how to actually *DO* PBR, and added code samples to the PowerVR SDK.

My original material:
https://docs.imgtec.com/PBR_with_IBL_for_PVR/topics/pbr_ibl_introduction.html

My colleague Tom Lewis is also turning this into a series of blog posts.

https://www.imgtec.com/blog/physically-based-rendering-powervr/

https://www.imgtec.com/blog/physically-based-rendering-with-powervr-part-2/