Outdoor SDF shaders use three light sources: sun key light, sky dome fill, and ground bounce

A minimal but realistic outdoor lighting rig has three components: (1) Sun / key light — a strong directional light, placed low for dramatic long shadows, yellow-orange in color. (2) Sky dome / fill light — the ambient blue light from the whole sky hemisphere, driven by dot(nor, vec3(0,1,0)) so upward-facing surfaces catch more sky. (3) Ground bounce — a faint upward-facing (dot(nor, vec3(0,-1,0))) yellow light simulating sun bouncing off the ground floor, preventing pure-black undersides. The complementary relationship between yellow sun and blue sky is an artistic advantage to push deliberately.

Examples

vec3 lin = sunDiff*sunCol*shd + skyDiff*skyCol + bounceDiff*bounceCol;

Assessment

Disable the sky fill light in a shader and describe three visual changes you observe on a sphere sitting on a ground plane.