Challenge 2: Why the Mug and Table Need Different Roughness Values — Solution Walkthrough

The answer:

Per Chapter 6's own material, Roughness controls how sharply or
diffusely light reflects off a surface, independent of whether an
object is solid, opaque, or metallic. Ceramic (the mug) and wood (the
table) both being solid, non-metal, opaque materials doesn't mean they
share the same surface finish — a glazed ceramic mug is typically
smoother and glossier than an unfinished or lightly finished wood
table surface.

Why "solid and non-metal" doesn't imply "identical material settings":

Per Chapter 6's own comparison table, Metallic being off on both
objects only rules out the specific metal-reflection behavior — it
says nothing about how glossy or matte either surface actually is.
Roughness is an entirely separate property from Metallic, and two
non-metal materials can still have very different Roughness values
depending on their own real-world surface finish.

Why matching each material to its own real surface matters:

Using identical Roughness values for both would make either the
ceramic look unrealistically rough or the wood look unrealistically
glossy — exactly the kind of mismatch this chapter's own material
warns against by emphasizing that these two properties alone define
most of what makes a rendered surface read as a specific real-world
material.

WHY THIS WORKS AS AN ANSWER
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This exercise checks that Roughness is correctly understood as an
independent property from Metallic, requiring its own thoughtful value
per material rather than being uniform across all non-metal objects.