Trying a little bit of illustration myself, as an indirect answer and for those who want to learn more about the shaders.
This is a simplified model obviously, converted to 2d, car shaders are used as example.
Green = object normals, also calculated visible surface points
Blue = camera point direction from object surface
Yellow = sun point direction from object surface
As shaders calculate every pixel (or "fragment" actually) of the visual objects that uses the material, also materials in the background unless they are discarded.
1. The normal facing sun position is about 90 deg away from sun direction = about 0 diffuse (first calculated range is 1.0 to -1.0, then range is limited to about , 1.0 to 0) I use range 1.0 to about -0.05 to make surface in shadow a little bit more bluish (take some sun color away) and limits everything below -0.05 to -0.05 as you can't have negative light, but I still use a tiny bit for simulated shadow.
Specular light almost 0 because sun does not reflect, from sun direction via normal direction to camera direction.
Ambient light about 90% (base) + extra from normals facing upwards (45deg away from 100% up)
Fresnel value (the effect where reflection amount is increased with higher view angle related to a surface) is low, as camera and normal is almost the same = low cube map
2. Normal facing about 45deg from sun direction => about 0.5 diffuse x texture(s).
So calculated diffuse is about 0.5 x sun light from the track file.
Sun direction reflects into camera direction in the normal direction, so specular light = close to 1.0
Ambient light about 90% (base) + extra from normals facing upwards (to have some extra sky reflection added to and increase cube map effect).
Fresnel value is quite high as camera angle is big compared to normal = high cube map and specular
3. Diffuse = high from sun and normal directions, about 1.0 x sun color x texture(s)
No specular, sun does not reflect to camera from normals direction.
Ambient light about 90% (base) + (extra added to cube map) from normals facing upwards (45deg away)
Fresnel value is quite high as camera angle is big compared to normal = high cube map and specular
4 - 6. Normals facing away from camera (not visible), simplified calculations to save performance. Texture x ambient only, as a little bit can be seen sometimes if some normals are heavily tweaked away from camera but a polygon still is visible.
7. Only base ambient x texture, no diffuse or specular
High fresnel, but doesn't matter, because cube map amount is also effected by diffuse light.
8. Almost the same as 7, less fresnel
There are also some numbers used in the shaders for fine tuning amount of some things in the calculations (to make it look better). These tweaks are made using the WTCC cars, to make them look as good as possible, so other mods may need some adjusting to look the best. That is why I update the super touring cars now,