Javadoc
This Filter does basically the same as a SpotLightShadowRenderer except it
renders the post shadow pass as a fullscreen quad pass instead of a geometry
pass. It's mostly faster than PssmShadowRenderer as long as you have more
than a about ten shadow receiving objects. The expense is the draw back that
the shadow Receive mode set on spatial is ignored. So basically all and only
objects that render depth in the scene receive shadows. See this post for
more details
http://jmonkeyengine.org/groups/general-2/forum/topic/silly-question-about-shadow-rendering/#post-191599
API is basically the same as the PssmShadowRenderer;