Described is a technology by which a GPU-based photon mapping mechanism/algorithm uses a kd-tree to render arbitrary dynamic scenes. For each frame, the mechanism emits and traces a set of photons into the scene. When a photon hits a surface, it can either be reflected, transmitted, or absorbed based on the surface material. Once photon tracing is done, a kd-tree is built for the stored photons. To estimate the radiance value at an arbitrary surface point, the k-nearest photons are located and filtered. The photon tracing and photon kd-tree construction, as well as the radiance estimation using k-nearest neighbor (KNN) searches are performed on graphics hardware, e.g., a GPU. In one example, only caustic photons are traced, whereby a photon is terminated and stored once it hits a diffuse surface.