This paper presents a novel image-based approach to render plausible soft shadows for complex dynamic scenes with rectangular light sources. The algorithm?s performance is mostly independent of the scene complexity and the source?s size. Occluders and receivers do not need to be separated and no knowledge about the scene representation is required, making the method easy to use. The main idea is to approximate the occlusion in the scene with prefiltered occlusion textures. The visibility of the light source at a point in space is estimated by accumulating the occlusion caused by each texture, using a novel formula based on probabilities.