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Dynamic area and volume lights are a common phenomenon in our world. Examples include illuminated advertising, video screens, and lava lamps. Yet rendering such light sources in real-time in interactive scenes remains challenging. In this paper we present a method to render area or volume light sources in a fully dynamic scene, i.e. the geometry, materials, camera, and lights (spatial and spectral composition) can change continuously. The key idea of our approach is to decouple lighting from shading complexity by using a dynamically generated hierarchy of irradiance volumes as an intermediate approximation of incident lighting. The main contribution of this paper is a new computation scheme that updates irradiance volumes directly on the GPU and enables real-time performance. The algorithm is very fast, runs on DX9-level hardware, and is easy to integrate into existing rendering pipelines, which makes it well-suited for games and virtual-reality applications. Current limitations of our algorithm are that it cannot handle shadows and provides only a coarse approximation for glossy reflection.