Area light soft-shadows! 🙂
Not physically accurate at all - just visually plausible. Shadow sharpness reacts to changes in dimensions, orientation and proximity of the emissive quad. Simple ray-tracing approximisations (no path-tracing, no stochatic-sampling/integration, no cone-tracing, no ray-matching, no sdf, no rasterisation, etc.) (pure-software, single-threaded)