Some more random npcs in C77 with PT on/off, NO MODS:
As you can see above it doesn't look good. No indirect lighting, only strong phong shading. Her plastic shirt looks horrible because it relies entirely on normal mapping with no lighting at all. Her eyes and fingers look horible because even at ultra lighting there is not enough resolution to cast proper self shadowing so everything "glows". And this is actually the best situation for normal rendering, close source of light singular.
Here PT resolves everything and that bad looking npc (which is standard pretty much in all open world games) becomes actually pretty nice looking lady. The little details like her fingers and eyes now are awesome, her plastic shirt makes more sense, quality of materials also rose up significantly and they aren't just texture blob.
Here is when you find no light near and game has to rely on fake lighting in game aka ambient light:
You know that look from playing other games. That's why developers don't like foggy areas etc. without adding strong lights somewhere in scene. She looks like PS4 character.
But let's give it PT treatment in scene where there is no direct light and only ambient scattered light:
Now it makes sense. Everything look correctly now. Her head doesn't look like Final Fantasy VII cloud anymore. Her bra/shirt also isn't flat but has intricate detail, bumps, meterial, it's streached etc.
Ever wondered why black skin characters look so wrong ? That's because a lot of what makes black skin color work is actually shadows and subsurface scattering. And with PT effects are dramatic:
Here without PT:
Looks like normal no. Pretty standard black person in game these days. Let's look at the guy with PT:
Yoooo, that's a different person alltogehter.
Another. This npc as far as npcs go in C77 is pretty good even without PT because his eyes aren't shown and his clothing is pretty simple.
But let's take this guy and give him PT treatment. Suddenly we go from good looking NPC to hero level in other games characters: