I wonder how these reflection functions are efficiently encoded in texture files. Would it be defined per polygon facets? per coordinate mapping on the texture?

I wonder if there are other, special case reflection functions for very specific lighting environments. For example, light that reflects mostly perpendicular to the surface, like something between Glossy specular and Retro-reflective.

It is really cool to see that the reflection models can be represented by bidirectional reflectance distribution functions. This allows the algorithm to calculate the radiance reflected by the material toward a specific direction. Maybe there are other functions that can model different physical properties like refraction?

What factors contribute to how the light reflects off an object? Is it based on the element that the object is made of (what properties of those elements?), thickness, the path light takes, or anything else?

these graphs are very illustrative in showing how reflections differ. it implies the intuition that the more mirror-like the surface is (glossier?), better the refection resembles a symmetric counterpart across the normal vector. for diffuse reflections functions, the light reflections are towards all directions, therefore we cannot see our mirror reflections

I wonders how to classify what type of reflection a given material be, does it only have to do to it's materials or does it also have to due with it's the angle and etc?

I'm curious to know what the word "ideal" is referring to in the first two names. I'm guessing it means that, in an ideal world, this is how the surface would react. However, since we don't live in an ideal world, what are some of the discrepancies and how do we reflect these discrepancies in our renderrings?

I think ideal here just refers to it 100% doing something, like being 100% reflective or 100% absorbed @ abaqai

Is there much difference between glossy specular and ideal specular? Can anything actually be ideal specular? If not, why do we make this distinction?

Why is the moon retro-reflective? It reflects the light of the sun toward the earth and that's why we can see it. If it is retro-reflective then it should reflect all the light back toward the sun?

is there a correlation between materials and the category of reflection functions? What other factors are there besides material that determine how light reflects? Can the interference of other objects change the reflection functions?

@nobugnohair I think this is because of the fact that some light from Earth is also reflected towards the Moon, which is why we can still see the faint outline of the Moon during a lunar eclipse (for example). This light is probably retro-reflected back to Earth, which is what this slide is referring to.

In terms of the actual real-life materials being modeled, what qualities of the material are most important when determining which category of reflection the material falls into? For example, it seems like the main difference between ideal specular and ideal diffuse is how smooth the surface of the material is, but what about glossy specular vs ideal specular? Both have a smooth, glossy finish, but what physical attributes of a glossy specular material sets it apart from an ideal specular material?