DDGI (Dynamic Diffuse Global Illumination)
A grid of light probes that gets re-ray-traced a little every frame, so indirect lighting can change in real time instead of being baked once and frozen.
Classic light probes are computed offline and go stale the moment a door opens. DDGI, published by Majercik, McGuire and colleagues at NVIDIA in 2019, lays probes out on a regular grid and fires a hundred-odd rays from each one per frame. The result is blended into the probe's irradiance map with a hysteresis factor, so lighting drifts towards its new state over a few frames rather than flickering.
The clever part is that each probe also stores the distance to the nearest surface. With that, the shader can tell when a probe sits behind a wall and ignore it — which is what otherwise produces the classic light leaking through walls. The technique ships as NVIDIA's RTXGI and has informed similar approaches in Lumen and other engines.