- Hosek-Wilkie inspired procedural sky (Rayleigh/Mie scattering, sun disk) - L2 Spherical Harmonics irradiance (9 coefficients, CPU computation) - SH evaluation in shader replaces sample_environment for diffuse IBL - GPU compute BRDF LUT (Rg16Float, higher precision than CPU Rgba8Unorm) - SkyParams (sun_direction, turbidity) in ShadowUniform Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>