Fast Robust and Precise Shadow Algorithm for WebGL 1.0 Platform

Abstract

This paper presents fast and robust per-sample correct shadows for WebGL platform. The algorithm is based on silhouette shadow volumes and it rivals the standard shadow mapping performance. Our performance is usually superior when compared with high resolution shadow maps. Moreover, it does not suffer from a number of artefacts of shadow mapping and always provides per-pixel correct results. WebGL 1.0 provides just vertex and fragment shaders. Thus, we put all our algorithms evaluating silhouette edges to vertex shaders. Specially precomputed data are fed to the vertex shaders that extrude shadow volume sides just for silhouette edges. Some optimizations are deployed for performance and data size reasons that are important especially on low performance configurations, such as cost-effective tablets and mobile phones. The paper evaluates our solution on number of models. Our solution performs on par with high resolution omnidirectional shadow mapping.