Abstract: The limited resolution of shadow maps (SM) may result in erroneous shadowing, yielding artificially jagged edges and temporally crawling shadows even using perspective optimization techniques. We introduce Sub-Pixel Shadow Maps (SPSM) for real-time shadow-mapping with sub-pixel precision. Our technique is based on the storage of a fixed-size partial representation of the scene geometry using conservative rasterization, combined with an original reconstruction of shadow edges. With only a small computational overhead our method avoids both perspective and projection aliasing. SPSM reconstructs shadow boundaries with thin details and high temporal consistency even using low resolution shadow maps. Our solution can also be used in conjunction with perspective optimization techniques where temporal and projection aliasing is hardly addressed. SPSM can particularly be used in demanding application such as games and real time rendering engines.