Original Phase 3a constants had SUN_DIR=(0.4,0.3,0.8) — heavily
vertical, so roofs and ground both landed near peak brightness and
only walls dropped. Combined with AMBIENT=0.4/DIFFUSE=0.6 the lit-vs-
shadow contrast was ~2.2x, which was real but hard to read through
textures. User feedback: "Ligtning looks the same I think."
Diagnosed with a temporary grayscale-lighting fragment output — walls
on different sides of the same building did show different brightness,
confirming the Phase 3a/3b pipeline is wired correctly end-to-end and
the issue was purely perceptual contrast.
Retuned: SUN_DIR=(0.5,0.4,0.6) (more oblique), AMBIENT=0.25, DIFFUSE=0.75.
Contrast ratio now ~3.3x. User-verified visually.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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