Abstract: Soft shadows and penumbra regions generated by extended light sources such as linear and area lights are visual effects that significantly con-tribute to the realism of a scene. In interactive applications, shadow computations are mostly performed by either the shadow volume or the shadow map algorithm. Variants of these methods for soft shadows exist, but they require a significant number of samples on the light source, thereby dramatically increasing rendering times.

In this paper we present a modification to the shadow map algorithm that allows us to render soft shadows for linear light sources of a high visual fidelity with a very small number of light source samples. This algorithm is well suited for both software and hardware rendering.