Extended PSM (XPSM) provides practical solution for real time shadows rendering. Distinguishing futures of this method from other shadow map reparameterization techniques is:
* high quality shadows, based on suboptimal projective space parameterization
* complete artifact reduction with correct post perspective space Z bias
* stability, free from singularities
* easy integration into any shadow map based engine
* patent clearance

Research paper, demo, code at http://xpsm.org