I'm currently learning how to use OpenGl, and I'm following a tutorial on learnOpenGL. I'm at the lightning chapter, and it has introduced basic lightning, ambient and diffuse with specular highlight. Phong shading essentially.
I'm confused about the ambient term. I understand that the ambient light is basically a light that comes from nowhere in particular, and it just fills the scene you're in with a soft light. And it's used to fake Global Illumination in renderers that do not compute it, so that the stuff that's not in the direct view of a light source is not completely black but it has some generic lightning on it.
So going by the definition, before actually trying to implement a renderer myself, and by using other engines like UE4, I always just assumed that ambient light would be a separate thing from say a point light or a directional light. I thought it would be a parameter independent of other stuff that would basically just light the scene.
But in the tutorial, at least for the basic lightning part, the ambient is actually part of the light "object" itself. Essentially every light source has its own ambient light.
This seems counterintuitive to me. Why does every light need an ambient part too? Wouldn't make more sense to have a "separate" ambient light object that provides the ambient light itself?
Also, if my light has a radius of say 100 units, then outside of that radius nothing will receive any direct light, obviously, but also no ambient and will be completely dark. Isn't the point of ambient light exactly not to have scenes without direct light go completely dark?
Most importantly I'm wondering if this implementation approach is the standard used in modern game engines, or if it's maybe a simplification in the tutorial. (For example I don't remember seeing a parameter for ambient light in the light objects themselves in UE4)