Lighting features of Iray Interactive render mode include:
Ray-traced, accurate hard- and soft-shadows
Accurate reflections and refractions
Efficient direct light sampling, including light profiles
Efficient multi-scale environment sampling. Initial coarse-scale approximation with low noise level converges quickly over time to an accurate result
Approximated indirect lighting (diffuse and glossy but diffuse-only on primary hit).
Fast, smooth approximation of matte ground shadows
Two ambient-occlusion modes (diffuse AO, AO guided by environment)