From Wojciech Lewandowski, "I made a minor tweak in StandardShadowMap.cpp. As agreed with J-S I have added AlphaFunc/AlphaTest to shadow camera stateset to make sure transparent objects will not cast blocky solid shadows."

src/osgShadow/StandardShadowMap.cpp

@@ -21,6 +21,7 @@
 #include <osg/Geode>
 #include <osg/Geometry>
 #include <osg/CullFace>
+#include <osg/AlphaFunc>
 #include <osg/Point>
 #include <sstream>
 
@@ -526,6 +527,12 @@ void StandardShadowMap::ViewData::init( ThisClass *st, osgUtil::CullVisitor *cv
         stateset->setRenderBinDetails( 0, "RenderBin", 
                             osg::StateSet::OVERRIDE_RENDERBIN_DETAILS );
 
+        // Assure that AlphaTest/AlphaRef works when redirecting all drawables to single bin.
+        // If AlphaFunc/AlphaTest is off - transparent objects will cast solid blocky shadows.
+        // No override to allow users change this policy in the model if really want solid shadows.
+        stateset->setAttributeAndModes
+            ( new osg::AlphaFunc( osg::AlphaFunc::GREATER, 0 ), osg::StateAttribute::ON );
+
         // agressive optimization
         stateset->setAttributeAndModes
             ( new osg::ColorMask( false, false, false, false ),
@@ -555,11 +562,6 @@ void StandardShadowMap::ViewData::init( ThisClass *st, osgUtil::CullVisitor *cv
         stateset->setMode
             ( GL_BLEND, osg::StateAttribute::OVERRIDE | osg::StateAttribute::OFF );
 
-#if 0
-        stateset->setMode
-            ( GL_ALPHA_TEST, osg::StateAttribute::OVERRIDE | osg::StateAttribute::OFF );
-#endif    
-
 #if 0 // fixed pipeline seems faster (at least on my 7800)
         program->addShader( new osg::Shader( osg::Shader::FRAGMENT,
             "uniform sampler2D texture;                                       \n"