Lighting lab

A sphere lit with the same physically based formula games use (GGX + Schlick Fresnel + Smith). Diffuse is the soft matte light; specular is the shiny highlight.

LitNormals viewFresnel view

DiffuseSpecular

Material

Albedo Roughness 0.4Metallic 0

Key lightAround (yaw °) 40Height (pitch °) 35Intensity 3

Fill lightAround (yaw °) -60Height (pitch °) 10Intensity 0.8

Rim lightAround (yaw °) 170Height (pitch °) 20Intensity 2.5

Try it

Set metallic to 1: the diffuse vanishes and the highlight takes the albedo colour.
Roughness 0.05 → 0.9: the highlight grows wider and dimmer, but the total light stays about the same (energy conservation).
Turn off Key and Fill: the rim light alone outlines the silhouette — that's Fresnel at grazing angles.