"Physically Based Rendering nvidia" and the first links point directly to nvidia's solution: iRay.
if you google
"Physically Based Rendering amd" you just get random articles on PBR and nothing that AMD has to offer - this despite the fact that AMD's ProRender (previously known as FireRender) offers that functionality.
Nvidia has been ahead of AMD in capturing this segment for a while now. They looked into the market for software that could benefit from iRay and pushed iRay towards them. For example Daz Studio from Daz3D.
This is a slide from 2015 from nvidia's GPU tech conference:
Here is the full presentation: http://on-demand.gputechconf.com/gtc/2015/presentation/S5536-Martin-Karl-LeFrancois.pdf
Basically they approached the Daz3D people and worked with them to develop an iRay solution (which supports nvidia GPU and CPU acceleration only) bundled free of charge.
Note that they are competing against LuxRender, which is a freeware PBR renderer made by a bunch of developers. But nvidia saw a huge market which could mean more sales of their graphics cards....
Can AMD also try to expand their ProRender technology to more software developers too?
|Application||AMD Support (ProRender)||Nvidia Support (Iray)|
|Autodesk 3ds Max||Yes||Yes|
|Cinema 3D||In progress?||Yes|
|Blender (Cycles)||In progress..||Yes (CUDA)|
AMD try to reach out to Daz Studios and more amateur rendering software developers too please.