Added preliminary GLSL shader path for volume rendering.
Added preliminary GLSL shader path for volume rendering.


openscenegraph/osg,jtorresfabra/osg,jtorresfabra/osg,openscenegraph/osg,marchelbling/osg,artoolkit/osg,tomasthoresen/osg,openscenegraph/osg,scrawl/osg,artoolkit/osg,artoolkit/osg,tomasthoresen/osg,scrawl/osg,scrawl/osg,scrawl/osg,marchelbling/osg,jtorresfabra/osg,tomasthoresen/osg,openscenegraph/osg,jtorresfabra/osg,marchelbling/osg,artoolkit/osg,tomasthoresen/osg,marchelbling/osg