In general, anything that looks like mid gray in the shader or the lights will take on new meaning when GC is enabled.  If that is being used to multiply something the impact can be huge.

Any small amount of injected luminance will be magnified. And it's not enough to look in Ambient_Color. It can be anywhere.

For example, the old V4 shaders used to have some very small amount of red injected when the light levels were low - faking subsurface scattering in shadows. That small amount of red becomes a really large amount of red when GC is enabled.

But those same shaders used some light cyan in specular to offset the added red. This was a suppression of red. The two effects were clever and carefully balanced in a way that only worked if you were doing non-linear rendering and only if the light levels were roughly the same as everybody is always using in portraits.

When GC is on, or when rendering with no lights (IDL only) or lots of other situations, those skin shaders turned all kinds of ugly colors.

Guess what - the correct shader under linear workflow is TWO NODES. That's right. It's SIMPLE.

Linear workflow is about removing hacks. It's about not having to guess. It's about not having complications.

 

---

Renderosity forum reply notifications are wonky. If I read a follow-up in a thread, but I don't myself reply, then notifications no longer happen AT ALL on that thread. So if I seem to be ignoring a question, that's why. (Updated September 23, 2019)