EatChildren
Currently polling second in Australia's federal election (first in the Gold Coast), this feral may one day be your Bogan King.
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I fixed the grass in The Witcher 2, and this appears exactly the same, so this is how it works; instead of draw distance being handled exclusively by the back end of the engine it's handled by per asset data, which the engine draws upon for information on namely for LOD transitions.
So for example in a lot of PC games you can tweak the engine cfg or ini files and find simple draw distance variables that will improve LOD transitions for more or less everything. From memory Source is a pretty good example of this. Basic commands will increase the LOD distance for all mesh/assets effectively eradicating LOD transitions and rendering everything in the highest quality over the longest possible distance.
In The Witcher 2 (and now The Witcher 3) that data is stored in the assets themselves. The engine pulls up grass, character, or whatever else, and that asset has tiers of LOD that the engine uses to calculate mesh complexity. The engine should, like The Witcher 2, have a mixed asset rendering distance command, so I'm surprised they're implying The Witcher 3 does not and I figure that's a mistake. In The Witcher 2 you could increase rendering distance of foliage and some assets, but it would still restrict LOD detail to whatever is hard coded into the assets.
In short, to fix the foliage rendering distance in The Witcher 2 I had to load up every single foliage asset individually in the editor and custom tweak the LOD one by one, then bake it into a mod for the game to use the "new" asset data.
Even then, I could never find a solution for characters, buildings, and some props. The general rendering distance command only works on some assets, excluding others (like characters, etc). So, for example, if you work out the draw distance rendering transition for a tent and the characters surrounding it, no line of command in the cfg or ini, nor any data in the assets themselves, could "fix" the pop-in. They were locked to their rendering distance.
That being said the engine still draws upon rendering distance tiers, so there should still be stuff like Rendering Distance = Low/Medium/High or whatever for performance reasons. But going beyond the maximum might not be possible. Unlike, say, Skyrim where increasing draw distance for everything is handled exclusively by the engine and very easy to tweak.