Iterative Lightmap Updates for Scene Editing

Lightmaps are popular for precomputed global illumination, but require costly recomputation when the scene changes. We present the theory and an iterative algorithm to update lightmaps efficiently, when objects are inserted or removed. Our method is based on path tracing, but focuses on updates to those paths that are affected by the scene change. Using an importance sampling scheme, our solution substantially accelerates convergence. Our GPU implementation is well-suited for interactive scene editing scenarios.