Wasn't Witcher 2 deferred? is that move really necessary? Dirt Showdown had forward+ and it didn't look convincing to be honest, not compared to other racing titles that are deferred anyway.
It was partial pre-pass on PC, but they switched to deferred shading on 360:
http://www.eurogamer.net/articles/digitalfoundry-the-making-of-the-witcher-2
LPP/Light Indexed DR & F+ are pretty similar."On Xbox we decided to go fully deferred, while on PC we used partial pre-pass - for skin shaders we have different lighting models (two specular values) and two passes that provided screen space subsurface scattering. We light an object and then apply albedo and specularity. Unfortunately we dropped it for Xbox, having to shrink down g-buffer due to optimisations," senior programmer Bartek Wroński explains.
Not sure exactly what you mean by convincing.
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PBR means that it's an energy conserving model. The BRDF models/equations will determine the look (artists) - material roughness/specularity.The footage so far don't look PBR, most materials look the same(AC4 type of look).
They might be referring to the light probes. Should give more accurate lighting information from the environment.I always thought image based methods are useful in reflections (cubemaps), but lighting? what good will they do compared to good lighting methods?